Upland Development Programme in Southern Mindanao (UDP)

STOP 1-4

SLOPE TREATMENT-ORIENTED PRACTICES FOR SUSTAINABLE

UPLAND FARMING AND SOIL CONSERVATION

including an Annex on

The effect of hedgerow layout on erosion and farm productivity

by K R S Proud

with illustrations by Ben Hur Viloria, SAD Component Coordinator

March 2006

A partnership programme sponsored by

the European Commission (EC) and the Government of the Philippines (GoP) and executed by the Department of Agriculture (DA)

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Foreword The permanent cultivation of upland in the humid tropics faces serious problems: a few days of moisture stress can reduce yields of annual crops intense rainstorms wash out nutrients and cause severe soil erosion, even on gentle slopes weed control is difficult high soil temperatures inhibit the accumulation of organic matter, complicating the replacement of nutrients and acid soils mean high rates of fertilizer applications are needed to be effective. To make matters worse, sheet erosion caused by growing coconuts, corn and cassava on sloping land in Southern Mindanao has reduced soil profiles by 50-100 cm over the last 20-30 years. Although land capability classifications indicate that most of the uplands are too fragile to support agriculture, people have been allowed uncontrolled access to plant annual crops - even on very steep slopes. As it is impractical to move one million people out of the uplands, the Upland Development Programme has opted to arrest the on-going environmental degradation by changing corn-based cropping to diversified farming with the emphasis on fruit and other trees that can be grown as cash crops. Farming systems analysts have identified the most promising development paths for permanent upland cultivation in the humid tropics. The first path is to re-establish a multi-storey cover of fruit and other cash crop trees on the slopes, and restricting corn and cassava production for home consumption to small gently sloping or terraced areas on the tops of hills or upper slopes. The second path involves a) reducing the time spent cultivating corn for home consumption on steep slopes by growing high yielding varieties of corn with inorganic fertilizers on corn patches one to two thousand square metres in area; and using the 2.5-3.5 months savings in labour to cultivate vegetables in intensively managed raised beds, either in the minor valleys, where irrigation may be possible, or as home gardens where scarce supplies of manures and composts can be concentrated most effectively. Including fishponds where feasible, and small-ruminants, such as goats, will provide extra income. This booklet describes the practices to be used for micro-scale planning at the farm level by local government agricultural officers and extension workers, in moving upland agriculture in the humid tropics along the development paths. If used correctly, extension workers should be able to provide upland farmers with appropriate, site-specific recommendations to protect their farms against erosion while increasing productivity and incomes. One of the steps taken by SAD in identifying replicable and sustainable models for permanent upland cultivation in the humid tropics was to review analyses of farming systems in similar climates in other parts of the world∗. Ruthenberg’s analysis emphasises that the permanent cultivation of upland in a hot humid climate “presents some of the most troublesome problems of tropical agriculture”. However, he identifies successful strategies adopted by smallholder farmers in the humid tropics from the Americas, Africa, South Asia and South East Asia and Australia, namely: dualistic cropping, multi-storey cropping, zero ∗ Ruthenberg, H (1983). Farming Systems in the Tropics. Third edition. Oxford University Press and Beets, W C (1990). Raising and Sustaining Productivity of Smallholder Farming Systems in the Tropics. AgBé Publishing. Alkmaar, Holland

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tillage and mulching, reduction in the area of annual crops to meeting the family’s food needs, and intensive cultivation of vegetables in gardens. If these strategies are replicable in areas with hot, humid climates+ across countries and continents, then they should be applicable and replicable in a similar climate in Mindanao. The very few economically viable systems of permanent upland farming that exist are found on very fertile alluvial or volcanic soils. Examples of permanent cropping which preserve the soil rely on intensive fertilising with organic and inorganic fertilisers, supplemented by erosion control measures, and intensive ploughing (e.g. in Taiwan), which is clearly impractical on the steep slopes in the uplands.

+ Humid climates have 7 or more humid months/year (>1,400 mm/yr). A very humid climate has 9 wet months

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SLOPE TREATMENT-ORIENTED PRACTICES FOR SUSTAINABLE UPLAND FARMING AND SOIL CONSERVATION

PESSIMISTIC VIEW OF THE UPLANDS • The general land development suitability of the uplands in the Davao Gulf Provinces is

considered as forest conservation areas. • The uplands are classified as not suitable for upland crops and half of the UDP-

covered areas are considered not suitable for orchard development. (The 1999 Planning Atlas for RegionXI. Davao Integrated Development Project (DIDP)

Japan International Cooperation Agency (JICA), March 1999.

PRAGMATIC APPROACH • It is too late to move the one million people living in the uplands on to other land. • The solution to arresting the environmental degradation in the uplands can only be

tackled by changing the “present farming system of annual corn-based cropping to one which is more appropriate with permanent and diversified cropping systems”. (Section 12.1, Annex 4 of the Financing Proposal for the Upland Development Programme)

STOP (Slope Treatment-oriented Practices) is a farm-level land suitability classification which identifies a choice of site-specific, environmentally-sound soil conservation strategies and diversified land use options based on slope, soil type and soil depth.

REASONS FOR OPTIMISM

“Introduced by the UDP in 2003, the diversified farming system using the Slope Treatment-oriented Practices (STOP), is a pioneering effort to improve upland farming for sustainable agricultural development…..it has surpassed expectations in helping preserve the resource base of the uplands and has also boosted farm production and income generation of farmers”. From; Sun Star Nov 25 2004.

END USER REACTIONS

• “I’m switching to bananas!” Farmer Santos Bidiot from Sto. Rosario, on realizing that he had spent P6,000 in labour to produce a corn crop worth just P2,800.

• “We have a word for that: Short!” A group of farmers in Marabatuan, after calculating that they had spent P9,600 in labour to harvest P6,000 worth of corn.

• “I have resigned from poverty!” Farmer Vicente Aliwanon from Del Pilar, on his greatly increased income after switching from corn to fruit trees.

• “My income averaged P1,000 a month when I grew corn. Now I only grow fruit and vegetables, and I get over P10,000 a month!” Saturnino Ellios, fromTaguibo

• “Despite my farm having steep slopes, by using the right technology it became a productive and replicable model for others to copy.” Pastor Guinang Fucal of Libi. His income rose from P4,000 from corn, to P20,000 a harvest after diversifying into bananas, pineapples, monggo, and fruits using STOP. His neighbours are copying him.

DISCLAIMER

The views expressed in this Report are purely those of the writer and may not in any circumstance be regarded as stating the official position of the European Commission

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TABLE OF CONTENTS Summary of STOP objectives for land care and diversified farming in the uplands

Land suitability issues Objective Approach Strategy Staff training Layout of the handbook

INTRODUCTION 1. Land classification 2. Suitability of the Southern Mindanao uplands for agricultural development 3. The need for site-specific soil and water conservation (SWC) measures 4. Slope treatment-oriented practices (STOP) 5. STOP 1, 2 3 and 4 6. Limitations to STOP

PART I 1. STOP 1: LAND UNIT FARMING Principle 1.1 Objectives 1.2 Land Units 1.3 Land unit mapping 1.4 Land unit farming 1.5 Restrict hedgerows to short lengths of slope <25% 1.5.1 Vertical Interval (VI) inappropriate for spacing hedgerows 1.5.2 Pineapples, sugarcane and cassava unsuitable as hedgerow plants 1.5.3 Problems arising from badly laid out hedgerwos 1.6 Hedgerow design using STOP 1.6.1 An improved design of cross-slope barriers 1.6.2 Objectives of new design for cross-slope barriers 1.7 Strategy for slopes too steep or too long for cross-slope barriers to be effective 2. STOP 2: MULTI-STOREY TREE CROPPING Principle 2.1 Importance of a vegetative cover in dissipating the erosive energy of rainfall 2.2 Lessons learned 2.3 Multi-storey tree cropping 2.4 Some planting sequences 2.5 Mulching 2.6 Maintaining soil fertility 3. STOP 3: ZERO-TILLAGE AND MULCHING Principle 3.1 How it works 3.2 The Problems 3.3 A Solution. STOP 3 –Zero-tillage (ZT) and Mulching 3.3.1 Zero-tillage (ZT) 3.3.2 Mulching 3.4 Environmental issues

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3.4.1 Herbicides 3.4.2 Safety precautions 3.5 Strategies of STOP 3 3.6 BSWM’s Balanced Fertilization Strategy 4. STOP 4: INTENSIVE PRODUCTION OF ANNUAL CROPS ON SMALL LEVEL PLOTS Principle 4.1 Objectives 4.2 Rationale 4.3 Strategies 4.3.1 Corn production 4.3.2 Vegetable production

4.4 THE CORN PATCH 4.4.1 Improved seed-fertiliser packages 4.4.2 Calculating the corn patch size to meet the annual corn requirements 4.4.3 Identifying areas suitable for the Corn Patch 4.4.4 Inputs and expected outputs from the Corn Patch 4.4.5 Demonstrating the corn patch 4.4.6 Recommended planting schedule 4.4.7 Comparing traditional corn production with the Corn Patch 4.4.8 Environmental aspects

4.5 RAISED BED VEGETABLE GARDENING Principle 4.5.1 Raised bed vegetable gardening 4.5.2 Advantages of gardening on Permanent Raised Beds 4.5.3 Site Selection 4.5.4 Bed Layout 4.5.5 Preparing a permanent raised bed 4.5.6 Preparing a crowned bed 4.5.7 Further actions to improve the site for permanent raised beds 4.5.8 Environmental issues

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List of figures Fig. 1.1 Improved design for cross-slope barriers on steep slopes Fig. 1.2 An impression of a landscape formed by land unit farming Fig. 1.3 Profile of a multi-storey tropical rain forest canopy Fig. 1.4 Profile of a slope planted with trees to produce a multi-storey effect Fig. 4.1 Farmer in corn field wonders how neighbour (with corn patch) has time to grow vegetables Fig. 4.2 Layout of permanent raised beds Fig. 4.3 Making the bamboo walls Fig. 4.4 The finished framework of a permanent raised bed Fig. 4.5 A crowned permanent raised bed Fig. 4.6 Using mosquito screening to break up raindrop impact on flowers

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List of Tables Table 1.1 Land qualities necessary for some farm production systems Table 4.1 Yields and production costs for a range of vegetables from one cropping season Table 4.2 Calculating corn patch size based on household requirements for corn grits Table 4.3 Inputs and outputs to produce corn for home consumption

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PART II STEPS TO USING STOP STEP 1: Draw a map showing the distribution of land units on farm STEP 2: Making and using the Slope Indicator STEP 2a: Making the Slope Indicator STEP 2 b: Using the Slope Indicator STEP 3: Determining soil texture in the field Notes on the characteristics of dry soils STEP 4: Slope Treatment-Oriented Practices for steep lands (STOP). Modified March 2006 STEP 5: Fill out the Land Unit Prescription Forms STEP 5 (a): Example of a Land Unit Prescription Form showing projected SWC inputs STEP 5 (b): Example of Land Unit Prescription Form showing projected incomes per land unit STEP 5 (c): Blank Land Unit Prescription Form STEP 6: Prepare map showing layout of SWC measures

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38 39 40 40 41 42 43 44

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ANNEXES Annex I The Effect of Poor Hedgerow Layout on Erosion and Farm Productivity

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SUMMARY STOP OBJECTIVES FOR LAND CARE AND DIVERSIFIED FARMING IN THE UPLANDS OF SOUTHERN MINDANAO

Land suitability issues Due to steep slopes and fragile, infertile soils, in 1999 the Davao Integrated Development Project (DIDP/JICA) classified the uplands of Southern Mindanao as not suitable for upland crops, and about 50% of the area as not suitable for orchard development. The only sound use recommended is as forest conservation areas. However, people have been allowed to settle there, and clear the forest cover from very steep slopes of critical watersheds to plant coconuts, corn and other crops without any restrictions. Reductions in soil depths of over 50 cm in the past 20 years (= 3 cm a year) under coconut plantations and on slopes, due to the continuous cultivation of corn and cassava, has proved this classification to be correct. The Upland Development Programme in Southern Mindanao (UDP), acknowledging that it is too late to move the one million people from the uplands to other lands, opted to arrest the on-going environmental degradation in the uplands by changing the “present farming system of annual corn-based cropping to one which is more appropriate with permanent and diversified cropping systems”. This is being achieved by identifying small areas, often only a few hundred square metres in area, within the rugged terrain of the uplands, that have the gentle slopes suitable for annual crops, and protecting them with appropriate soil and water conservation measures (SWC). On long, steep slopes, corn is being replaced with bananas and fruit trees. It should be noted that UDP’s experience with SALT technology confirms that of other projects and soil conservationists: that SALT is only applicable on very few sites at the tops of hills with short slopes of less than 20%. By referring to the UDP’s Slope Treatment-Oriented Practices (STOP), a land suitability classification designed for micro-scale planning at the upland farm level, appropriate site-specific SWC measures and land use options, can be identified. Objective The objective of STOP is to promote a change from unplanned upland agriculture, in which annual and perennial crops are planted anywhere, regardless of slope or soil depth and texture, to a planned one where crops are matched to the most appropriate slopes and soils. For over 90% of upland farmers growing corn as a cash crop has proved to be financially disastrous, as labour costs are more than the value of the crop. Diversifying into bananas, fruit trees, and vegetables, lessens dependence on a single crop, ensures food security, and increases productivity and income generation. However, it requires recognition that the land itself imposes limitations on what is ecologically sustainable. Technically speaking, the use of Vertical Interval (VI) as a basis for spacing hedgerows is not appropriate if the aim is just to slow down the run-off and let it filter through the barrier, rather than to intercept and divert it to a waterway of some kind. Under STOP 1 hedgerow spacing is based on depth of soil, slope and cultivation requirements, to ensure that 50 cm depth of soil remains at the back of the terrace to support crop growth. The UDP recognises that self-sufficiency in food is an important consideration to many upland farmers. Farmers are therefore encouraged to grow sufficient corn to feed their households until such time as the tree crops produce regular and reliable incomes sufficient

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to purchase household staples. Planting high-yielding varieties of corn on a 1,000-2,000 m2 corn patch, and using the recommended applications of fertilizer, will provide the farmer with his household needs for corn and free 75-105 mandays of labour per year for other uses. The 80-90% reduction in the area needed for corn releases land for planting income-generating banana and fruit trees. Approach

• Restrict the cultivation of annual crops to sites receiving the least amounts of run-off, i.e. the shorter gentler slopes of crests and ridge tops, where cross-slope barriers such as hedgerows, suited to slopes below 20%, become appropriate soil conservation measures.

• Plant contour grass hedges of Napier Grass or Vetiver Grass at approximately 4-m intervals on short 12-15 m lengths of upper slopes up to 45%. Two-metre wide natural vegetative strips (NVS) occupy the land immediately below the Napier-Vetiver grass hedges and are planted with bananas. Use the remaining 2-m wide strip to grow annual crops. Contour cultivation and the processes of erosion will form terraces over a 3-5 year period.

• Replace annual crops with a mixture of tree crops and grass cover on long slopes or steep slopes up to 55%, that cannot be terraced, and that generate large volumes of run-off with highly erosive velocities.

• Practice zero tillage and mulching on shallow soils less than 60 cm deep on gentle slopes (<25%). Above 25% slope, the wisest choice is to plant perennial crops.

• Reduce the risk of erosion on shorter slopes with rapidly steepening convexity by converting to medium- or long-term crops and sod-forming grasses (not cogon).

• Plant fruit trees by direct seeding followed by field-grafting of scions. This is particularly important on soils that have eroded down to <60 cm depth, as the tap-roots of the seedlings can penetrate through cracks in the rocky substrata to find moisture. Nursery-produced seedlings, which lose their taproots, have fibrous root systems near the surface and are more prone to drought.

• Develop high value vegetable production on raised beds in minor valleys. • Farmers can save 76-105 days of labour by growing high-yielding varieties of corn

for home consumption on 1,000-2,000 m2 corn patches and applying inorganic fertilizers.

• Options for farms dominated by slopes greater than 55% include planting small-crowned fruit trees from seed and field-grafting on scions; intensive backyard vegetable gardening on permanent raised beds, livestock or fish production around the homes of farmers, and working off-farm.

Strategy Model farms should be easily visible and accessible from roads and footpaths, and have a range of minority land units (crests, ridges, small valleys), so one or more of the following changes can be demonstrated:

− Substituting corn-based farming on steep slopes with perennial crops. − Relocating the production of erosive crops (e.g. corn, root crops) to the limited

areas of gently sloping land units (e.g. hill tops) and planting high-yielding varieties to compensate for the reduced area under cultivation.

− Terracing fallow land with clay-textured soils over 100 cm deep, on upper slopes below 45%, through a combination of grass strips and contour ploughing.

− Converting unproductive cogon grassland to fruit tree orchards (slopes 55%). − Intensifying vegetable production by improving backyard systems, or on land

where supplementary, gravity-fed watering is possible.

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Staff training Extension workers should be trained in:

− recognising land units such as crests, ridges, or valley bottoms, etc. with potential for sustainable cropping of annual crops.

− farm mapping to differentiate areas of high potential for annual crops (including upper slopes that can be terraced), from slopes suitable for trees; and

− applying the STOP menu of site-specific prescriptions to cover the wide range of combinations of slopes and soils occurring in the uplands.

Layout of the handbook Part I of this handbook describes the four STOP strategies developed so far: Land unit farming (STOP 1), which aims to restrict the area suitable for annual crops to upper slopes by using cross-slope barriers and contour ploughing to promote terracing; Multi-storey tree cropping (STOP 2), in which mixtures of fruit trees of different heights replace annual crops on slopes too steep or too long for cross-slope barriers; and Mulching and Zero Tillage (STOP 3), to be applied when soils are too shallow for applying STOP1; and Intensive Production of Annual Crops on Small Level Plots (STOP 4) which advocates adopting the corn patch approach to produce corn for home consumption which frees 75-105 days of labour for more productive activities such as intensive vegetable production, planting fruit trees, etc. STOP 4 also provides guidelines on intensifying backyard vegetable gardens in permanent raised beds as another option to cultivating annual crops on steep sloping land. Part II gives details on how to make and use the laminated slope indicator, and assess soil texture in the field. Blank Land Unit Prescription Forms are provided along with examples of completed forms and farm maps.

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INTRODUCTION

1. Land classification

Land classification places strict limitations on certain lands according to their location in the landscape, their slope, and soil depth, texture, etc.

Land suitability is the fitness of a given type of land for a defined use, either in its present condition or after improvements. By grouping land units according to their suitability for specific kinds of land use unsustainable land use practices are avoided on fragile lands. The health of the land can be preserved until technologies are developed permitting sustainable exploitation while conserving soil and water.

2. Suitability of the Southern Mindanao uplands for agricultural development

Upland soils are highly sensitive to disturbance and low in resilience. Their use for agriculture precipitates or accelerates land degradation. The fragile nature of the soils and the rugged terrain dominated by steep slopes limits the area of land suitable for agriculture.

The land capability maps in the DIDP/JICA 1999 Planning Atlas for Region XI1 show the uplands of the Davao Gulf Provinces as suitable as forest conservation areas, but over 90% of the UDP-covered barangay areas are not suitable for upland crops, with about 50% of the UDP area considered unsuitable for orchard crops.

Despite this, people have been allowed to settle in the uplands, and clear the forest cover from very steep slopes without restrictions. The long-term cultivation of corn and cassava, and coconuts on the fragile soils and steep slopes, has resulted in massive reductions in soil depths. Throughout the UDP areas farmers say soils are more than 50 cm shallower than 20 years ago (an average loss of 2-3 cm per year), with over 100 cm lost since the 1960s in some ancestral lands. Declining crop yields and periodic crop failures are normal.

Because it is impractical to move one million people out of the uplands, the UDP opted to try to change the corn-based cropping to diversified farming systems (DFS), to arrest the on-going environmental degradation. For over 90% of upland farmers, growing corn as a cash crop has been a financial disaster. The labour costs greatly exceed the value of the corn produced. All farmers agree, however, that growing bananas can be profitable (giving 2-10 times the income than corn), with lower labour costs and much less land degradation.

3. The need for site-specific soil and water conservation (SWC) measures

The “traditional” SALT leguminous hedgerows, initially tried by the Project, proved to be inappropriate SWC measures for the long, steep slopes found in much of the uplands. Reasons to doubt the suitability of hedgerow intercropping on steep slopes2, 3 include:

− they were designed for gentle slopes below 20%; − the very close spacing required on steeper slopes, and consequent reduction in

cultivable land, make hedgerows unacceptable to some farmers; − they do not prevent a build up in volume and velocity of run-off on long slopes.

4. Slope treatment-oriented practices (STOP)

Although the uplands have been classified as unsuitable for agriculture at the macro-scale, there are small areas, often only a few hundred square metres in area, within the steep uplands that are suitable for crops. These land units, with short slope lengths and gentle slope gradients, include plateaux, hill tops and crests, ridges, and minor valleys. 1 Japan International Cooperation Agency (JICA), March 1999. Davao Integrated Development Project (DIDP), Planning Atlas. Pacific Consultants Internatonal 2 Young, A (1989). Agroforestry for soil conservation. Wallingford UK, CAB International 3 Hudson, N (1992). Land husbandry. London. Batsford

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To exploit these areas of relatively high agricultural potential, UDP developed the STOP land suitability classification as a tool for micro-scale planning at the farm level. Based on slope angle, soil texture and soil depth, it takes into account farmer objectives, farm size, cost of labour, and proximity of markets. One hectare of land that includes slopes, hill tops and minor valleys is enough to provide an annual income of over P100,000 if the correct management practices are applied. For example, by reducing the gradients of upper slopes through a combination of cross-slope barriers and contour ploughing, and planting a variety of short-, medium- and long-term crops matched to appropriate slope ranges and soil types.

STOP restricts annual crops to areas where the erosion hazard is lower (i.e. on gentler slopes at the top of hills or in minor valleys) or where the hazard can be lowered (i.e. by applying appropriate SWC measures). Long or steeper slopes, where cross-slope barriers are not effective in controlling run-off, are set aside for tree crops.

By taking three simple field measurements: slope angle; soil texture, and soil depth, the agricultural extension worker can sub-zone the upland farms into land units (see Part II). Based on the characteristics of the land units, and their location in the landscape (e.g. hill top, ridge, upper slope, minor valley, etc) the STOP table provides site-specific prescriptions for annual crops, vegetables and fruit trees, and the appropriate SWC measures. The extension worker draws maps of the farm showing the land units and recommended lay out of SWC measures, and in consultation with the farmer prepares a prescription form outlining the land use options for each land unit and the recommended SWC measures.

5. STOP 1, 2, 3 and 4

To date, four forms of STOP intervention have been developed (see Part I):

− STOP 1: Land unit farming, which aims to extend the area suitable for annual crops by using cross-slope barriers and contour ploughing to promote terracing on the upper slopes where erosion risks and run-off rates are lower. Since poorly designed and laid out hedgerows can damage a farm’s potential, an improved design for cross-slope barriers is presented which combines 2-m wide natural vegetative strips with contour hedgerows. This increases the distance between the hedgerows and improves soil conservation. Bananas planted in the NVS generate higher incomes than if the area was left to corn. The cultivable strips can be planted with any crop once they have been properly protected with cross-slope barriers.

− STOP 2: Multi-storey tree cropping, in which mixtures of fruit trees of different heights replace annual crops on slopes too steep or too long for cross-slope barriers.

− STOP 3: Mulching and Zero Tillage, to be applied when soils are too shallow for forming terraces under STOP1.

− STOP 4: Intensive production of annual crops on small level plots, in which the area used to grow corn for consumption is reduced by 80-90% to a corn patch, and the savings in labour used to grow vegetables in permanent raised beds in the backyard and in minor valleys, as well as planting and tending fruit trees and bananas.

6. Limitations to STOP

There are many areas where the STOP soil and water conservation interventions cannot be safely or effectively implemented without increasing the erosion hazard. This may be due to excessively steep slopes, slope length and shape, highly erodible lahar soils, or severely truncated soil profiles overlying stone substrata. In these circumstances the DA and UDP should leave the decision to the DENR Secretary as to whether it is in the public interest that upland farmers be permitted to continue to try farm to these lands.

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PART I

1. STOP 1 LAND UNIT FARMING

PRINCIPLE: MINIMISE THE PROBLEMS OF SOIL EROSION BY RESTRICTING THE CULTIVATION OF ANNUAL CROPS TO MINOR VALLEYS AND FLAT TO

GENTLE SLOPES, OR UPPER SLOPES WHERE CROSS-SLOPE BARRIERS REDUCE SLOPE GRADIENTS BY PROMOTING TERRACE FORMATION. RESERVE STEEPER AREAS FOR PLANTING TREE CROPS FROM SEED.

1.1 Objectives

STOP 1 provides site-specific recommendations on the maximum intensity of land-use permitted and the type and spacing of soil and water conservation measures for a given piece of land, based on its slope, soil texture and soil depth (see Part II).

1.2 Land Units

A block of land with the same slope range and soil type is termed a land unit. It can be expected to have the problems and potentials for agriculture as similar areas of land elsewhere in the landscape. They are areas of land that are recognizable by their position in the landscape (e.g. a plateau, a hill crest, ridge, upper slope, mid-slope, spur, minor valley, etc). However, when the underlying geology changes, the width and length, slopes, soils and dissection of land units, may also change. The boundaries of a land unit occur where there is a distinct break in the slope. 1.3 Land unit mapping

The Bureau of Soils and Watershed Management (BSWM) has mapped the soils and land resources in many municipalities. However, the maps are at scale 1:25,000, which means the minimum area that can be mapped is 10 ha. But many upland farms are only 3-7 ha in area on dissected terrain. Areas of gently sloping land suitable for growing annual crops are scarce in the uplands, with blocks rarely exceeding 0.5 ha, and too small to be shown on the BSWM maps. Land unit mapping shows the presence of these areas of gentle slopes for farm planning purposes. Land unit mapping involves the following steps (see Part II for details):

Step 1: Sketch a map (overhead-view) showing the whole farm area, and the the different land units (crests, ridges, upper slopes, side slopes, minor valleys, etc). Base boundaries on easily visible, major breaks in slope.

Steps 2 & 3: Measure the slope and soil depth, and assess soil texture. Estimate the area and the current land use of each land unit.

Step 4: Refer to the STOP table for recommended land uses and SWC measures. Step 5: Write a prescription for each land unit in the land unit prescription form.

Specify the proposed land use and the soil conservation measures needed for the particular land unit. The inputs needed for each land unit (Step 5a) and estimated incomes for various crops (Step 5b), can also be included.

Step 6: Prepare a second map showing the layout of the proposed SWC measures.

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1.4 Land unit farming

Land unit farming is the development of crops on a series of land units usually, but not necessarily, from the top of a hill to the valley depending on their land qualities for agricultural crops (Table 1.1) and their susceptibility to erosion. Table 1.1 LAND QUALITIES NECESSARY FOR SOME FARM PRODUCTION SYSTEMS

ROOT CROPS

Soils: Loose, deep, free-draining soils, well-structured and free from compaction. Preferably loamy soils, with little stoniness. Shallow soils to be avoided.

Slopes: Flat to gentle slopes (12%) or on terraces on steeper slopes.

Drainage: Well-drained soils important.

Others: Animal manure or mineral fertilisers are necessary to maintain fertility.

VEGETABLES

Soils: Light workable soils, preferably alluvial or volcanic, which retain fertility and structure.

Slopes: Flat to gentle slopes (0-12%); low risk of erosion.

Drainage: Good drainage. Proximity to water supplies would be an advantage.

Others: Good shelter. Access to markets.

SEMI-PERENNIALS e.g. pineapples, bananas Soils: Pineapples can be grown on a wide range of soils. Prefer sandy loams with pH 5-6.5. Bananas grow on a wide range of soils. The best soils are fertile, of volcanic or alluvial origin. Low pH favours spread of Panama disease in Gros Michel bananas.

Slopes: High erosion results if pineapples are grown without mulching on steep slopes. Bananas should be hilled up on steep slopes, and planted on the contour with adequate soil conservation measures.

Drainage: Pineapples do not tolerate water-logging. Bananas require good drainage. Others: High calcium and manganese content in soil results in chlorosis in pineapples. High sodium chloride content is deleterious for bananas, but they respond well to added N and have a high K requirement.

FRUIT TREES Soils: Wide range of soils acceptable but less suitable on shallow sandy soils due to risk of drought. Avoid waterlogged soils. Slopes: Flat to steep slopes (up to 58%) depending on size of mature tree. Drainage: Good to moderate, or moderate to imperfect. Others: Good grass cover with little encroachment of cogon (Imperata cylindrica). Supplementary water is advisable if high value fruits are to be grown.

1.5 Restrict hedgerows to short lengths of slopes <25%

SALT hedgerows are not an appropriate soil conservation strategy on long slopes (i.e. more than 30 m) or slopes greater than 25%. STOP 1 restricts the cultivation of short-term crops to hilltops, crests, ridges, upper slopes and minor valleys, where terraces formed by

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hedgerows reduce slope gradients. Cross-slope barriers consist of a hedgerow or lines of Vetiver or Napier grass, planted accurately on the contour using an A-frame, with a 2-m wide NVS immediately below, planted with banana trees (see Section 1.6). 1.5.1 Vertical Interval (VI) inappropriate for spacing hedgerows

Using VI as a basis for spacing is not appropriate if the hedgerows are intended just to slow down the run-off and let it filter through the barrier. This design procedure should be applied only if the terrace is designed to carry away all run-off 4. The appropriate form of terracing for humid tropical regions are reverse-sloped terraces5 which are designed to intercept and divert surplus run-off into grass waterways or drainage lines.

1.5.2 Pineapples, sugarcane and cassava unsuitable as hedgerow plants

Plants such as pineapples, sugarcane and cassava should not be used as hedgerows. By their nature they are not permanent barriers and they do not produce tillers to fill gaps between plants. The soil built up behind contour rows of pineapple and cassava barriers increases the erosion hazard when the crops are harvested or replaced.

1.5.3 Problems arising from badly laid out hedgerows

Problems that arise when hedgerows are too widely spaced or soil depths are too shallow (see Annex 1) include:

− infertile subsoil is exposed at the back of the terrace giving poor crop production. − the riser height between terraces becomes too high (can exceed 3 metres) increasing

the kinetic energy of run-off and accelerating erosion; − drying out of the risers may lead to terrace collapse; − skeleton soils are formed when the topsoil overlying coarse deposits is washed

away; − the increased infiltration of rainfall runoff can cause land slides.

1.6 Hedgerow design using STOP

Under STOP 1, hedgerow spacing is based on a soil depth of at least 100 cm, slope and cultivation requirements. Provided there is a minimum soil depth of 100 cm, the spacings between the SWC measures given in the STOP Table (see Part II, Step 4) ensure a minimum soil depth of 50 cm will remain for growing crops at the back of the terrace when level bench terraces have developed.

1.6.1 An improved design of cross-slope barriers

Figure 1.1 shows an improved design for cross-slope barriers on steep slopes when applying STOP on undeveloped land. It incorporates a 2-m wide NVS immediately below the hedgerow, which will dissipate the energy of run-off dropping from the terrace above so it doesn’t undermine the terrace. The spacings given in STOP apply only to the width of the cultivable strip. The cross-slope barrier now includes both the leguminous hedgerow or Napier/Vetiver grass strip and the NVS.

Bananas in the NVS, and a row of pineapples at the NVS/terrace interface prevent ploughing into the NVS, and help diversify the farming system. Crops that can be productive with less water and therefore suitable for planting in the shallower 30-50 cm deep soil at the back of the terrace include the leguminous monngo bean, and the relatively drought-tolerant pineapple.

4 Hudson, N (1992). Land husbandry. London. Batsford (p 98) 5 FAO (1986) Watershed management field manual Slope treatment measures and practices. FAO Conservation Guide 13/3.

16

Fig. 1.1 Improved design for cross-slope barriers on steep slopes

Because the prescriptions for a given land unit can be extrapolated to similar land units occurring in the same landscape, which may cover several square kilometres, land unit farming can be considered to be a replicable model for upland development.

1.6.2 Objectives of the new design for cross-slope barriers:

The new design aims to produce terraces on steep slopes by using soil movement from erosion and contour ploughing over 3-4 years. The function of the NVS is:

• to reduce the riser height of the terrace and minimise the risk of terraces collapsing by absorbing the impact of run-off passing through the barrier.

• to act as an alternative to planting additional contour hedgerows when hedgerows are too widely spaced. Mark out the width of the cultivable strip appropriate to the slope steepness and extend the width of the NVS beyond 2-m.

• rather than reducing incomes, the NVS can yield higher returns than corn if bananas or other fruit trees are planted in it.

1.7 Strategy for slopes too steep or too long for cross-slope barriers to be effective

A mixture of fruit trees should replace annual crops on slopes too steep or too long for cross-slope barriers. This is best done by direct seeding, followed by the field-grafting of scions when the young trees have pencil-thin stems (see STOP 2: Multi-Storey Tree Cropping). Fruit trees grown from seeds planted in the field develop stronger root systems and live longer. This may be an essential strategy to ensure survival if soil depths have been eroded to depths less than 60 cm. Figure 1.2 illustrates a landscape after land unit farming has been adopted.

Slope Terrace width 12-25% : 4.0 m 26-35% ; 3.0 m 36-45% : 2.0 m

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Fig. 1.2 An impression of a landscape formed after land unit farming

Terraces, for growing annual crops, have formed on the less steep hillcrest and upper slopes because of soil interception by cross-slope barriers. Trees, in a triangular spacing, are growing on the steeper mid- and lower slopes from seeds directly planted into well-mulched planting site. Vegetables are grown on raised beds in the more fertile alluvial soils in the minor valleys.

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2. STOP 2 MULTI-STOREY TREE CROPPING

PRINCIPLE: IMITATING THE MULTI-STOREY CANOPY OF THE ORIGINAL RAIN FOREST, BY PLANTING A MIXTURE OF TREES OF DIFFERENT HEIGHTS, PROTECTS THE SOIL FROM EROSION BY DISSIPATING THE ENERGY OF RAINDROPS.

A MULCH OF DEAD LEAVES ON THE SOIL SURFACE IMPROVES INFILTRATON AND REDUCES SHEET EROSION AND RILLING.

2.1 Importance of a vegetative cover in dissipating the erosive energy of rainfall

Vegetation intercepts and dissipates the kinetic energy of raindrops before they reach the soil, preventing the detachment of soil particles. The main function of cover crops such as Pueraria, Calopogonium and Centrosema is to protect the soil from the impact of raindrops falling from the canopy - particularly tall trees when drops may approach their terminal velocity. A disadvantage is that the shade produced by the established tree crop may cause the cover crop to die out, preventing a satisfactory ground cover from developing. Cover crops on slopes do not prevent rill erosion.

Soil losses of 360 t/ha/yr under industrial plantations such as coconuts reduce soil depths by 3.0 cm/yr. Under undisturbed tropical rain forest soil losses are just 6 tons/ha/yr.

The much lower rate of soil erosion under tropical rain forest, even on steep slopes, is due to its multi-storey canopy (see Fig. 2.1) and mass of feeder roots just under a thick layer of litter on the forest floor. These combine to protect the soil from the direct impact of falling rain and increase its porosity. By enhancing infiltration of rainfall into the soil, the amount of run-off is reduced, and stream flows are maintained through the year.

Figure 2.1 Profile of a multi-storey tropical rainforest canopy

Emergent

Canopy

Understorey

2.2 Lessons learned

A UDP study found that slopes of 75-80%, protected by a mixed tree cover of coconuts, bananas, fruit trees and ipil-ipil, and a soil mulch of dead leaves, had soil depths of over 80 cm. Less than 50 m away, years of cultivating corn on slopes of 50% had reduced soil depths to 20-50 cm.

The closer the soil cover resembles the upper canopy and protective undergrowth or leaf mulch of the natural forest, the lower the rates of soil erosion.

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2.3 Multi-storey tree cropping

For a highly productive, sustainable, permanent upland cultivation to succeed in the humid tropics soil erosion must be kept to a minimum. This is best achieved by imitating the tropical rainforest that originally covered the soils. Multi-storey tree cropping, in which a mixture of trees and shrubs are planted together, is a good solution (see Figure 2.2).

The canopy of natural forests and a ground cover of dead leaf litter is most effective at reducing erosion. A dense growth of sod-forming perennial grasses on the slope is as effective but, for adequate erosion protection at least 70% of the ground surface must be covered. However, the shade of an established plantation kills off most of the grass under the trees, unless they are widely spaced.

Figure 2.2 Profile of a slope planted with trees to produce a multi-storey effect

2.4 Some planting sequences

Slopes unsuitable for arable crops should be given over to tree crops, preferably planted in rows running east-west to avoid shading and to maximize the utilization of solar radiation. Different types of tree are planted in sequence. For example:

Stage Plants to be planted Comments 1 Banana, citrus, ginger Rows oriented E-W. 2 Coconut, mango or durian, lansones Rows oriented E-W between the 1st stage trees 3 Coffee, cacao, jackfruit, medicinal plants Plant in the shade produced by the 2nd stage trees

With established coconut plantations start by planting bananas, citrus, coffee and ginger to get short-term and medium-term income. Phased cropping gives a continuous supply of food, fruits and fibre, and spreads labour requirements through the year.

2.5 Mulching (see also STOP 3)

Because cleared land doesn’t have the layer of dead leaves found on the floor of the original forest, the planting sites of the seeds or seedlings should consist of a 3-meter diameter circle heavily mulched to a depth of 30 cm (e.g. using cogon). A layer of 2-3 coconut fronds should be used to mulch ginger. The mulch retains soil moisture during dry spells, improves soil porosity, and helps support soil micro-organisms. Eventually, the leaf litter from bananas and coffee will also provide the mulch to protect the soil. The rate of mulch formation can be increased in a number of ways:

− The fine leaves of Acacia falcata planted as a shade tree (e.g. for durian) help mulch the soil. The Acacia trees, cut after four years, can earn P400 a stem.

B = Banana C = Coconut M = Mango G = Ginger

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− Arachis pintoi (forage peanut) forms a good cover. It can form a mulch of dead leaves if sprayed with a non-systemic herbicide. The live cover should regenerate from the roots.

2.6 Maintaining soil fertility

Under natural conditions the tropical rain forest recycles between 12-30 tons of organic matter per hectare every year. This maintains the ecosystem on infertile upland soils because, under normal circumstances, it is a closed cycle – nothing is removed. However, substantial amounts of N, P and K, and micronutrients are removed in fruits harvested from trees planted in soils depleted of nutrients by crops of corn and cassava. If the system is to be sustainable the nutrients removed need to be replaced. This is most effectively replenished in the form of a mixture of composts or manures and inorganic fertilizers. (See STOP 3 below for role of dead leaf litter in maintaining the nutrient cycle).

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3. STOP 3

MULCHING AND ZERO-TILLAGE

PRINCIPLE EMULATING THE ORIGINAL FOREST FLOOR BY COVERING THE SOIL

WITH A THICK LAYER OF MULCH PROTECTS IT FROM RAINDROP IMPACT, IMPROVES INFILTRATION OF RAINFALL, RETAINS SOIL

MOISTURE, AND ENCOURAGES SOIL MICRO-ORGANISMS. ZERO-TILLAGE INVOLVES PLANTING SHORT-TERM CROPS

THROUGH THE MULCH WITHOUT TURNING THE SOIL. 3.1 How it works

Layers of compost, in various stages of development, cover the natural forest floor: freshly fallen leaf litter, barely decomposed leaf litter, partially mature compost, mature compost, then the soil. A root mat draws nutrients from the compost layers. With minimal removal of forest products such an essentially closed nutrient recycling system6 has successfully supported the high biomass and bio-diversity of the tropical rainforest for hundreds of thousands of years.

However, when leaves, fruits, shoots, and roots are continuously harvested, the nutrients removed from the soil must be continuously replaced from outside sources. This is especially important to maintain a sustainable agriculture system. 3.2 The Problems

The expansion of impoverished smallholder farming producing unfertilised arable crops on depleted soils in the tropical uplands destroys forests and wildlife and causes serious erosion. For example, in Vietnam the continuous cultivation of hill rice and cassava has resulted in one million hectares of eroded skeleton soils with no value for agriculture or forestry7. If this happens in the Philippines there will be a mass exodus from extensive areas of the uplands. The treeless landscapes and shallow soils will exacerbate the risk of flooding in the lowlands.

The continuous cultivation of corn and cassava on sloping lands in the UDP areas is resulting in soil depth reductions of 2-4 cm per year. In some areas soil depths have been reduced from over 85 cm to less than 25 cm. Because shallow soils are unable to store sufficient soil moisture to support plant growth during the dry season, crop failures will become more frequent and the land may be unable to support tree crops. Efforts must be intensified to increase the awareness of the problems facing the uplands and effect a change to tree crops as soon as practical. 3.3 A Solution: Mulching and Zero-tillage (ZT)

STOP 3 is an attempt to address the problem of how to grow short-term crops when there is less than 100 cm depth of soil needed for terracing under STOP 1. The objective is to maintain the present soil depth by preventing any further movement of soil down slope. As with STOP 1, growing short-term crops will have to be restricted to gently sloping hilltops and ridges and minor valleys. Drought-tolerant Vetiver grass should be planted as cross-slope barriers to keep soil in place, as other hedgerow species are likely to die off.

6 Depending on soil type and vegetation between 8-25 t/ha need recycling annually to sustain the undisturbed forest 7 Thai Phien and Nguyen Tu Siem (1996). Management of sloping lands for sustainable agriculture in Vietnam. In: The Management of Sloping Lands in Asia. (IBSRAM/ASIALAND. Network Doc #20 pp. 275-314

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Most tree crops will not survive on shallow soils. Short-season crops such as monggo (mung beans), or drought-tolerant crops such as pineapples and sorghum, will make more efficient use of the limited amount of moisture stored in shallow soils. ZT (see 2.2 below) must be adopted to minimise exposure of the soil to the erosive impact of raindrops. Heavy mulching will be needed to prevent any further reduction in soil depths and to conserve soil moisture. Tree crops with tap roots will have to be planted from seed, as their tap roots can penetrate cracks in the ‘hardpan’ and access deeply stored moisture. 3.3.1 Mulching

Mulching is the covering of the soil to simulate the effect of the leaf litter-covered forest floor. Suitable materials include crop residues (e.g. corn stalks, rice straw or rice hulls, coconut fronds, sawdust or wood shavings). If cogon or other grasses are used, they should be cut before they set seeds to avoid creating a weed problem. To be effective a mulch should cover at least 70-75% of the soil surface.

Mulching improves the soil’s ability to absorb rainfall and slows down the drying out of the soil during the dry season. This can be particularly important when planting the durian. Durians do not have root hairs. The roots that absorb water and nutrients are fungus roots which grow out from the secondary or tertiary roots, and which grow only within about 50 cm of the soil surface. Without a deep layer of mulch to keep the soil moist, the fungus roots die off affecting the growth and productivity of the tree.

Mulching also protects the soil against erosion; prevents soil temperatures from getting too high; and suppresses weed growth. Crop residues used as mulch increase or retain the level of organic matter in the soil, stimulate soil organisms, and make the use of chemical fertilizers, such as phosphates, more effective if they are applied on top of a layer of mulch, than if they are applied on bare soil8. However, as organic mulches decompose they compete with the main crop for nitrogen. Pests such as termites and snails, which harm the crops, may be attracted. 3.3.2 Zero-tillage (ZT)

As its name implies, ZT (also termed minimum tillage, no-till, etc.) is a system of crop production where the soil is not ploughed or loosened with hand tools. Instead of tillage, the seed is planted directly into the soil. The main features of ZT are:

− Spraying with herbicide 3-5 days before planting to replace hand-weeding, or ploughing and harrowing as the way to control weeds (this saves time and money).

− Planting seeds in holes made by hand using sticks to make the opening (dibbling). − Using fertilisers and crops that produce a large amount of residues, otherwise

mulching materials have to be obtained from outside the farm. − Establishing a continuous cover of crops by intercropping techniques. − Retaining the crop residues as a mulch to reduce evaporation and limit weed growth. − Applying pesticides to control insect pests that spend part of their life cycle in the soil.

Advantages of Zero-tillage Considerable savings in time, labour and cash can be gained by spraying with herbicides. UDP farmers have found that applying herbicides to control cogon saved them between P2,500 to P9,700 per hectare in labour costs. This has increased their incomes, which is one of the UDP’s main objectives. Examples are as follows:

8 See “A Guide to Mulching Fruit Trees” prepared for UDP by KRS Proud, Tree Crops Consultant. September 2003

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• Observations at Sitio Mamada, Brgy Andap, New Bataan, Compostela Valley, show the value of using herbicides by replacing the function of tillage for weed control, and applying inorganic fertilizers and mulching to maintain fertility9. Two hectares of dense cogon grass were cleared with P2,000 worth of systemic herbicide taking 2-3 mandays. It usually took 20 man-days of labour (@ P100/day) to clear the area, but the cogon needed several more cuttings to eliminate it. It was not possible to grow maize with the cogon present. As they consider maize cultivation to be unsustainable, farmers eventually plant the area with fruit trees.

• At Brgy Tibulao, Carmen, Davao del Norte, Mario Alburo took 40 days to clear a ridge top for corn using four ploughings with a carabao at a cost of P12,000. However, he found that the cost of land preparation by spraying herbicide to kill cogon was only P 2,720 over 2-3 days. The early planting of corn enabled him to follow up with a crop of beans giving him extra income.

• The risk of losing the investment by planting fruit tree seedlings in Cogon lands is very high. Spraying systemic herbicides on the green leaves kills the subterranean rhizomes, leaves a layer of organic mulch to provide the seedlings with nutrients, and reduces competition for moisture and reduces soil erosion. An outlay of P193 for herbicides and inorganic fertilizer is enough to establish 30 trees in cogon lands: − P25 for herbicide to clear the 210 m2 of cogon covered land (@7 m2/ tree) and, − P168 for 12 kg inorganic fertiliser for 30 trees in the first year @ 100 g/ tree

/qtr after the first year). 3.4 Environmental issues

3.4.1 Herbicides

It must be emphasized that upland farmers tend to apply herbicides as a one-off measure to control Cogon. Normal hand weeding of the crop is done once the land has been cleared. Application rates of herbicide for controlling noxious weeds such as cogon vary from 0.3 to 4.0 kg/ha. The environmental impact if spraying herbicides in STOP 3 is expected to be miniscule. The rate of herbicide application is equivalent to applying one tablespoonful of herbicide in one litre of water over plant leaves covering 45 m2 of soil. By comparison, the depth of water from applying 50 litres of water in the 19 m2 root zone around a coconut tree is just 2.0 mm. There is no danger of contaminating ground water supplies. There is a perception that herbicides are harmful to soil micro-organisms, even though the micro-organisms are largely responsible for removing harmful chemicals from the field. Research shows that a mixture of two widely used herbicides actually stimulated microbial activity10. 3.4.2 Safety precautions

As noted above, farmers have learned independently that buying and applying herbicides can save them considerable labour and cash. In the interests of safety LGUs should therefore be advised to train technicians in the appropriate way to handle herbicides, and 9 Ruthenberg, H (1983). Farming systems in the Tropics. 10 Krutz, L.J., Senseman, S.A., Haney, R.L. 2003. Effect of Roundup Ultra on atrazine degradation in soil. Biology and Fertility of Soils. 38:115-118.

24

on the precautions to take (clothing to wear, avoid spraying on windy days, etc). Farmers can then make use of the services of these technicians when required.

3.5 Strategies of STOP 3

In summary, the strategies of STOP 3 are:

a) Boost organic matter production To generate sufficient mulching material in the first year it may be necessary to plant crops such as HYV corn, to produce large amounts of crop residues. Plenty of inorganic fertilizer, particularly N, will boost the production of corn stalks, especially on shallow soils to offset the nutrients lost through harvesting.

b) Keep the soil covered with a layer of mulch In the second year: establish a continuous cover of crops by intercropping to maintain soil fertility by N-fixation and biomass recycling instead of fallowing. Mulches of crop residues and fast-growing cover crops (e.g. Arachis pintoi) suppress the growth of weeds, protect the soil from raindrop impact and promote infiltration. Shading the soil from the sun minimizes oxidation of organic matter.

c) Practice zero tillage (ZT) Instead of tilling the soil to bury or kill weeds, spray with herbicide, and use a stick to plant (or dibble) the seeds through the mulch formed by the dead weeds and/or the large amounts of plant residues accumulated in the previous year). ZT enhances biological activity under the mulch. Higher infiltration rates result by reducing soil compaction.

d) Diversify crop production Diversify production by growing a wide range of crops to minimize the impact of price fluctuations, and damage to any particular crop by diseases and insect pests. Include legumes such as monggo (mung beans) in the rotation to maintain soil fertility. Plant vegetables in the minor valleys where soil eroded from the slopes accumulates, and water is available (see STOP 4: permanent raised beds).

e) Apply fertilizer on top of the mulch Many short-term crops develop a dense mat of feeder roots that penetrate the mulch, just like forest trees. As there are not enough nutrients in the available organic matter to sustain a vigorous crop of vegetation, apply fertiliser on top of the mulch to avoid ‘burning’ the crop roots. Phosphate fertilizers, in particular, are more effective if they are applied this way, as contact with bare soil makes P unavailable to plant roots. P inputs are needed to sustain crop yields on the highly weathered soils of the uplands. Deficiency of P prevents nodulation by legumes, resulting in low levels of N-fixation and increased competition between crops for available P.

3.6 BSWM’s Balanced Fertilization Strategy

BSWM advocates a Balanced Fertilization Strategy (BFS)11. BFS is the optimum use of organic and inorganic fertilisers to supply the correct ration of plant nutrients so that soils can sustain high crop yields over long cropping seasons. It aims to ensure stable production of affordable supplies of basic staples as well as ensuring the sustainable productivity of high value crops. Location specific recommendation is one of guiding principles of BFS.

11 Launched by BSWM in 1997 under Presidential Proclamation No. 1071

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4. STOP 4 INTENSIVE PRODUCTION OF ANNUAL

CROPS ON SMALL LEVEL PLOTS

PRINCIPLE SMALL INTENSIVELY CULTIVATED PLOTS OF ANNUAL CROPS CAN YIELD HIGHER RETURNS PER HOUR OF WORK THAN LARGER, POORLY TENDED

FIELDS. THE EFFICIENT PRODUCTION OF FAMILY FOOD REQUIREMENTS FREES LAND AND LABOUR TO PLANT PROFITABLE PERENNIAL CROPS,

WHILE OFF-FARM INCOME CAN BE USED TO IMPROVE FAMILY WELFARE.

4.1 Objectives

The primary aim of STOP 4 is to reduce the area planted under corn by 80-90%, while still achieving the food security priorities of the farmer. Freeing sloping land for planting fruit trees helps reduce land degradation. By producing food for home consumption more efficiently the farmer can invest more time to producing fruit and vegetables as cash crops. Off-farm income, previously earned to make up the shortfall in food production, can be invested in the farm or used to improve the family’s welfare (paying school fees, better housing, clothing, etc).

4.1 Rationale

In general, upland farmers spend excessive time and effort to grow the corn needed to feed their families. The five or six operations needed to secure a harvest of corn in the uplands can take 35—60 man-days work. With only one furrow covered per operation, the distance walked per hectare is 13.333 km per operation– or a minimum of 80 km travelled per harvest! Two ploughings to just 15 cm depth, loosens and turns over almost 4,000 tons of soil. Erosion on sloping land causes soil losses of 360 - 1,000+ tons/ha/yr, equivalent to a reduction in soil depth of 3-10 cm per year. This decreases corn yields still further and damages the potential of the land to plant tree crops, which need deep soils to store the sufficient moisture to survive during extended periods without rain.

Despite spending over 100 days growing corn, the low yields from growing native varieties of corn on depleted soils are insufficient to meet household requirements. Farmers then either work off-farm to the P3,600-6,300 needed to buy the shortfall of 200-350 kg of grits, depending on family size. At P80-100/day this can amount to an average of 36-45 days work. Some farmers are dedicating 5-6 months a year just to produce food to feed the family, without any generating any income. All the effort is wasted if a drought causes crop failure, and the farmer has to borrow money.

With such inefficient use of manpower, it is obvious why there is widespread poverty in the uplands. Spending less time on household food production means off-farm income can be used to improve the family welfare. Many upland farmers have discovered that planting fruit trees and bananas frees them to earn cash elsewhere, and they can buy their household staples and pay for other services things with the income from selling fruits. HYV varieties of corn are available in the municipalities that yield 5-7 tons of shelled corn per hectare. This is equivalent to 0.5 kg/m2 corn compared to the native varieties which give 0.04 kg/ m2. Planting these high yielding varieties of corn can reduce the area the farmer needs to plant by 80-90%. Growing vegetables can be very profitable. High yields can be obtained from small areas of land. E.g., 0.25 ha can produce up to 15,000 kg of tomatoes per season (see Table 4.1).

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Table 4.1. Yields and production costs for a range of vegetables from one cropping season (averaged to 0.25 ha). BSWM12

Vegetable Yields (kg/0.25 ha)

Production costs (Pesos/0.25 ha)

Production costs (Pesos/kg)

Eggplant 8,031 22,111 2.75 Tomato 15,000 25,960 1.73 Pechay 12,500 64,688 5.19 Ampalaya 49,917 288,656 5.78 Squash 22,500 15,998 0.71

Data from one farmer-respondent, Brgy Sto Rosario, San Isidro, Davao Oreintal

Ampalaya (the highest earner) yielded a net income of P430,094 from 0.25 ha ( P172/m2). 4.2 Strategies

4.3.1 Corn production The cost of inputs (HYV seed and complete fertilizer and urea) needed to grow all the year’s requirement for corn on only 25-45% of the off-farm income earned just to make up the shortfall in supply! In other words, by investing in a HYV seed/fertilizer inputs the farmer actually saves money, as well as time and releases land for other purposes. Identify small areas (1,000 -2,000 m2) of flat to gentle slopes, and help the farmer set up a Corn Patch (see Section 4.4). By showing the effectiveness of seed-fertiliser technology packages farmers will realize that a modest investment in inorganic fertilisers can secure their subsistence food requirements. They are then more likely to apply the considerable savings in time and labour to managing more profitable perennial crops and earning off-farm income to benefit the family through education, house improvement, health, etc. 4.3.2 Vegetable production Look for small areas on the farm, even short lengths of steep slope will do, preferably near a supplementary supply of water, and show how to set up Vegetable Gardens on Permanent Raised Beds (see Section 4.5). Each 1 m x 10 m bed will hold 3.5 cu metres of soil. In Malamudao, Compostela Valley, spring onions planted in permanent raised beds can earn the farmer P100/m2. Is the work too much? A 1.0 x 10.0 m bed holds about 3.5 cubic metres of soil. So preparing 20 beds would need a maximum of 70 cu m of soil. This is not a lot of soil compared to the 4,000 tons of soil loosened and turned over by the farmer each season for corn by two ploughings to 15 cm depth. The returns are certainly worthwhile. 20 beds at 10 m2 per bed gives 200 m2. This can give a potential income of between P20,000 - 30,000 a season, depending on the range of vegetables planted.

12 Bureau of Soils and Water Management (2004). Soils and Land Resources Evaluation of San Isidro, Davao Oriental. Soil and Land Resources Information Series. April 2004.

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4.4 THE CORN PATCH - GROWING CORN FOR HOME CONSUMPTION ON SMALL PLOTS

PRINCIPLE USING IMPROVED SEED-CHEMICAL FERTILISER TECHNOLOGIES CAN

REDUCE THE AREA USED TO CULTIVATE CORN FOR HOME CONSUMPTION BY 80-90%. THIS RELEASES LAND AND LABOUR FOR PLANTING THE STEEP SLOPES WITH TREE CROPS OR THEY CAN BE LEFT UNDER FOREST COVER 4.4.1 Improved seed-fertiliser packages

Improved varieties of corn have been developed to give high yields when combined with inorganic fertilizers. The yields to be derived from applying the recommended basal dressing and side-dressings of fertilizer need demonstrating over two seasons to show that the household needs for corn can be obtained from very small areas with correspondingly less effort.

4.4.2 Calculating the corn patch size to meet the annual corn requirements

Assumptions o 1.5 kg of shelled corn produce 1.0 kg of grits. o Expected yields from the HYV corn to be planted are 5,000 kg/ha/harvest or

higher. OPV corn is cheaper to buy than hybrid varieties but the labour and fertiliser needed on the 25% increase in area of corn patch, to make up for the lower yields, can be more expensive than buying the hybrid corn.

o For each harvest 1.0 m2 of corn patch is expected to produce 0.5 kg shelled corn giving 1.0 kg shelled corn/ m2 of corn patch per year.

When finding out the household’s daily requirements for corn grits, distinguish between what is cooked and what is actually required, as there are times when some families do not have sufficient food to prepare. The objective is to grow the household annual needs.

Table 4.2 shows how to extrapolate from kg grits needed per day to the kg of shelled corn needed per month to be produced to prepare the grits. The annual amount of shelled corn needed to produce the required amount of grits represents the minimum size of the corn patch. These sizes can be rounded up, e.g from 1,080 m2 up to1,200 m2.

In cases where a large household requires amounts that exceed those given in Table 4.2, e.g 6 kg of corn grits a day, simply refer to the Table and add together the corn patch sizes for 2 kg and 4 kg grits/day families, or double the area needed for 3 kg grits/day. Both calculations give a corn patch of 3.240 m2.

Table 4.2 Calculating corn patch size based on household requirements for corn grits

Grits/day (Kg)

Grits/mo. = Col. A x 30kg

(Kg)

Shelled corn/mo. = Col. C x 1.5 kg

(Kg)

Shelled corn/yr = Col. D x 12 mo.

(Kg)

SIZE OF CORN PATCH (1.0 kg shelled corn needs 1.0 sq

m) (Sq metres)

2 harvests/yr 3 harvests/yr

2 60 90 1,080 1,080 720

3 90 135 1,620 1,620 1,080

4 120 180 2,160 2,160 1,440

5 150 225 2,700 2,700 1,800

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4.4.3 Identifying areas suitable for the Corn Patch

One or more small blocks of land can provide the total area needed for the corn patches. The crests of hills and gently sloping land protected with properly contoured and spaced hedgerows or other cross-slope barriers are ideal. Small blocks of land in the vicinity of the farmer’s homestead on flattish land, with contour NVS to control soil erosion are ideal. Shade tolerant varieties of corn, if available, are recommended under coconut trees.

4.4.4 Inputs and expected outputs from the Corn Patch

Example: − A household requirement of 3 kg grits a day is equivalent to 135 kg of shelled

corn a month for food = 1,620 kg per year (see Table 4.2), requiring a 1,620 m2

corn patch. − Average yields of hybrid corn (GSI47) on loam soil = 5,280 kg/ha. This should

give about 850 kg of shelled corn per harvest from 1,620 m2, or a total of 1,700 kg from two harvests.

− Table 4.3 shows the inputs required to harvest 1,700 kg corn. Note the low amount of labour involved. An outlay of about P2,284 (including P1,000 of labour) per harvest gives P7,650 worth of shelled corn (@ P9/kg) if the farmer has to buy it to mill into grits for home consumption.

− 10-12 days of off-farm work each season will provide the funds to buy the inorganic fertiliser needed to grow half the family’s food supply.

Table 4.3 Inputs and outputs to produce corn for home consumption (purchase price of P18/kg)

Inputs Per hectare Per 1,620 sq m Cost/ 1,620 sq m Seed corn 18 kg 3.0 kg P292*

Expected yield 5,280 kg 850 kg Fertiliser Complete

Urea

200 kg (=3 g/hill) 200 kg (=3 g/hill)

32 kg 32 kg

P480 P512

Total cost of inputs P1,284 Labour 60 man days 10 md @ P100/day P1,000

COST/HARVEST P2,284 TOTAL COST/YEAR P4,468 Average yield/year 10,560 kg shelled corn 1,700 kg shelled corn Value = P15,300

* Assumes a 18 kg sack of seed corn costs P1,800 4.4.5 Demonstrating the corn patch

The extension technician must personally deliver the herbicides, seeds and fertilizers at the relevant stages to ensure the inputs are not misplaced, or sold, and must be present:

− spray cogon and weeds with herbicides to ensure the appropriate herbicide (e.g. systemic type for cogon) and the recommended amount of herbicide is mixed with water for the size of the corn patch13, and that the required safety procedures are followed (see 3.4.2 Safety precautions, above).

− planting to ensure the farmer plants the seeds of improved corn at the recommended number of seeds per hill and the spacing within rows and between rows. If the bag recommends planting one seed per hill, then that

13 In one instance farmers had mixed the entire 2.25 litres of herbicide with an equivalent volume of gasoline, when only 18 tablespoons (equivalent to one sardine can) were needed. Despite mixing with gasoline they were still going to mix one sardine can of the mixture with water – when two sardine cans of the mixture were now needed. As the gasoline floated on top of the herbicide the correct amount of herbicide might not have been applied to be effective.

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should be followed. Planting two seeds, as is usual practice, but only applying the recommended 3 g/hill of complete fertilizer as a basal dressing, and 3 g/hill of urea as a side dressing, provides only half the amount of fertilizer per plants. Yields will be reduced in these cases. (If one seed per hill is recommended, the small area of the corn patch should allow the farmer to replant any gaps caused by ungerminated seeds).

− the application of the top dressings and side dressings of fertilizer to ensure the correct amounts are placed. Reducing the recommended amounts will lower yields (see comment above regarding exceeding the recommended number of seeds per hill)

4.4.6 Recommended planting schedule

After preparing the land with the recommended spacing between the rows for the variety of hybrid corn (usually 70 or 75 cm apart), plant the seeds at the correct number per hill (sometimes this is just one seed a hill) and at the correct spacing within the row(18-25 cm apart). Apply a basal dressing of complete fertiliser (usually 3 g per hill – measured with the cap from a small bottle of mineral water) at the recommended time after planting. The fertiliser should preferably be covered with soil to minimise its dissipation (“burning off”) into the atmosphere due to exposure to sunlight. Weed the patch if needed before applying the side dressing of urea (3 g/hill). About 30 days before harvesting the cobs, plant beans or peanuts between the corn stalks. The crop residues should be left as a mulch on the soil surface, or ploughed in, to maintain soil organic matter levels and reduce leaching of fertilisers. The sale of beans or peanuts may offset the cost of the fertilizer.

Once the bananas and fruit trees planted on slopes formerly planted with corn start bearing fruit, the farmer may find that he can increase his income still further by converting the corn patch to bananas and buying corn for his family to eat – as farmers have discovered elsewhere in Southern Mindanao.

Figure 4.1 The farmer on the left, with a large corn field on steep slopes, wonders how his neighbour has time to tend vegetables and tree crops and still grow enough corn to feed hise family. The answer: a small corn patch planted with HYV corn and properly fertilized frees the manpower for the other tasks

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4.4.7 Comparing traditional corn production with the Corn Patch

Scenario 1 Traditional cultivation of corn (based on field data from Davao Oriental)

• Farmer X needs 800 kg grits a year for home consumption (i.e. 1,200 kg shelled corn).

• He currently plants 7,500 m2 of flat land each season with native corn. • Each harvest cycle takes 54 mandays of labour @ P80/day, and 18 carabao days

@ P 100/day. • Total cost for two seasons = 108 md or P8,640 plus P1,800 for carabao hire. Cost

of corn production = P10,440 • Harvesting 450 kg shelled corn per harvest, or 900 kg a year, leaves a shortfall of

300 kg (= 200 kg of corn grits). To buy the shortfall in grits costs him P18/kg (i.e. P3,600), requiring 45 days work off- farm.

• Total outputs to obtain 800 kg corn grits = P14,040 (P10,440 + P3,600). • Cost of purchasing 800 kg corn grits = 800kg x P18 = P14,400

If the farmer had bought his household’s requirement of 800 kg corn grits direct at P18/kg it would have cost him P14,400. So his net savings by growing corn by traditional means and purchasing the 200 kg shortfall of grits = 14,400-14,040 = P360 (equivalent to 20 kg of corn grits).

RESULT: 153 man-days were spent just to get enough corn for home consumption. =============================================================== Scenario 2

The farmer grows high yielding variety (HYV) of corn in a Corn Patch

• To get 600 kg shelled corn a season (to produce 400 kg grits) he only needs to plant 1,200 m2 of land with 2.2 kg HYV of corn, and apply 23.5 kg complete fertiliser as a basal dressing and 23.5 kg urea as a side-dressing.

• Labour costs: 8.5 man-days and 3 carabao days/season = P880 or only 17 man-days/yr.

• Total cost for two seasons = P 1,960 labour + P1,857 seed-fertiliser package = P3,714

• BUT 6,300 m2 of land is no longer used for corn production. If planted with 630 cardava banana suckers, producing 10 kg bananas per hill @ P2/kg, then his income goes up by P12,600

• The 136 days of labour saved can be used to earn an off-farm income of P10,880 to spend on improving the quality of life of the family, or to invest in the farm.

RESULT: Only 17 days spent on corn production while freed land and time can

earn income of P23,480 to pay for fertiliser and improve family welfare, pay school fees, etc.

============================================================== 4.4.8 Environmental aspects

Concerns about the danger of ecological damage arising from using chemical fertilisers in the uplands should take into account the following:

− The farming systems analyst, Hans Ruthenberg, has been pointed out that: “hardly anything is as destructive in terms of maintaining a balanced

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environment as the expansion of impoverished smallholder farming producing unfertilised arable crops on depleted soils in a tropical setting. Destruction of forests, eradication of wildlife, and serious soil erosion, are the accompanying phenomena”.

− The very small amounts of chemical fertilisers (<50 kg) used to restrict the production of annual crops to small plots (<0.1 ha) has to be offset against the loss of hundreds of tons of soil per hectare each year from current practices.

− Over-use by upland farmers is unlikely as inorganic fertilizers are expensive. The problem is to ensure that farmers apply the specified amounts to gain the full benefits of increased yields, as applying small amounts of fertiliser per hill are relatively ineffective.14

− The amounts of herbicides applied are miniscule. If cogon is present, a 1,620 m2 corn patch requires about 36 tablespoons (approximately the volume of 2 sardine cans). The alternative is more damage: on sloping land farmers have been seen chipping off the layer of cogon rhizomes, taking with it 2-3 cm of depth of soil. The soil is loosened further during land preparation exposed to the direct impact of rain. Another 2-3 cm depth of soil can be expected to be washed away.

14 H Ruthenberg (1983): Farming Systems in the Tropics. OUP (page 363).

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4.5 VEGETABLE GARDENING IN PERMANENT RAISED BEDS

PRINCIPLE GARDENING HAS BEEN THE TRADITIONAL SOLUTION TO THE PROBLEMS FACING PERMANENT CULTIVATION IN THE UPLANDS THROUGHOUT THE HUMID TROPICS 15. BY APPLYING INTENSIVE GARDENING TECHNIQUES,

VEGETABLES CAN BE CULTIVATED SUCCESSFULLY IN UPLAND SITES EVEN ON POORLY DRAINED INFERTILE SOILS DESPITE

INTENSE SUNLIGHT AND HEAVY UNRELIABLE RAINFALL 4.5.1 Raised bed vegetable gardening

As the name implies, the level of the soil in raised beds is higher than the surrounding soil. Upland farmers currently use temporary beds formed from ridges of soil, but these need to be built up every season because the impact of rain and cultivation flattens them out. The soil on and between the beds is frequently compacted by the farmer walking between the rows to tend to the crops. Standing water causes localized water-logging which lowers yields.

Permanent raised beds are surrounded by a framework or border, such as boards or bricks. This contains the soil and maintains the shape of the beds from season to season. As such they are ideal for a number of situations:

− On sloping ground and hillsides, where erosion can be controlled by a combination of terraces and permanent beds.

− On soils with a high clay content and tendency to become water-logged. Raising the height of the soil allows the surplus water to drain out of the soil.

− On subsoil or hard pans where root penetration is difficult. As most vegetable crops obtain most of their water and nutrients from the top 30 cm of soil, constructing raised beds can be used to artificially increase soil depth.

4.5.2 Advantages of gardening on Permanent Raised Beds Because of the following advantages, properly managed raised garden beds can produce 1.4 to 2 times more vegetables per square metre than ordinary beds.

a) Soil compaction avoided Soil compaction can reduce crop yields up to 50 percent as it affects the movement of water, air and roots through the soil. Because there is no need to walk on a raised bed, the absence of compaction improves oxygen availability for plant roots.

b) Waterlogging prevented Sites liable to ponding can be made productive by raising the beds to prevent water-logging, which affects plant development by depriving roots of oxygen. This is an important factor when growing vegetables in minor valleys where clay soils may become saturated with run-off from adjacent slopes. Permanent raised beds can be planted during periods of heavy rainfall, whereas temporary beds need good weather for bed formation.

c) Soil depths increased Raised beds provide sufficient depth of soil for most vegetables. They are therefore very useful in areas where soils have become shallow due to erosion or other factors.

15 Garden cropping is distinguished by (1) production of small amounts of produce from a great number of different food crops: (2) small plots; (3) proximity to the house; (4) fencing; (5) mixed or dense planting of a great number of annual, biennial and perennial crops; (6) a high intensity of land use; (7) land cultivation several times a year; (8) permanence of cultivation; and (9) cultivation with hand implements.

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d) Soil conditions improved Raised beds enable the farmer to change the soil texture to suit the type of vegetable he wants to grow in a bed, e.g. by adding more sand or clay soil, or mixing in more organic matter. Small amounts of lime can reduce soil acidity and maintain it in the 5.8 to 6.8 pH range preferred by vegetables. Covering the beds with plastic mulch gives some control over soil moisture content. A small site can therefore have beds with different soil types to suit the range of vegetables to be grown.

e) Yields increased Plants can be spaced far enough apart to avoid crowding but close enough to shade out weeds. Higher densities are possible over a 1.0 m-wide bed than when the crop is planted in single rows separated by furrows. Good management may give yields of 3-6 kg vegetables per m2.

f) Inputs more efficiently used Expensive fertilisers, scarce manures and the limited supplies of compost, mulch, and water can be applied more efficiently as they are only spread on the cultivated beds.

4.5.3 Site Selection Raised beds can be used on a wide range of soils because they have good drainage.

− Sandy loam soils are ideal for raised beds as they not likely to get waterlogged. − The water-holding capacity of sandy soils can be increased by adding compost. − The texture of heavy clay soils can be altered by adding sand and organic matter. − On shallow soils where subsoil or hard pans prevent root penetration, raised

bed constructed to a height of 30cm provide sufficient depth for most vegetable crops to extract their water and nutrients.

4.5.4 Bed Layout

a) Bed orientation Plan the layout of the vegetable garden carefully. Beds constructed side-by-side and parallel to each other are easier to build, maintain and irrigate (see Figure 4.2). If space allows, beds for different vegetables should be aligned to the sun as follows:

− Align beds for tall crops requiring trellises (tomatoes, long beans, peas etc) in an East-West direction to get the optimum amount of light.

− Plant lower-growing crops on the south side of the beds so that the taller crops don’t block the sun and align them in a North-South direction to allow direct sunlight to strike both sides of the beds.

Figure 4.2 Layout of permanent raised beds

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b) Bed dimensions The wider the bed, the lower the construction cost per square metre. Wider beds make better use of space as fewer pathways are needed. This can be important when the area of land suitable for vegetable gardening is limited.

i) Bed width A bed width one metre (100 cm), but not more than 1.2 metres, reduces the need to step on the beds during crop management, and avoids compacting the soil.

ii) Bed length A bed 1 m wide x 10 m long provides 9 sq m of usable space. Leave 0.6 m (60 cm) as a walkway between beds, makes for easy movement between beds. Mulch the spaces between the beds or cover them with slabs of carabao grass turf or stones to prevent them becoming muddy and slippery when wet.

Warning: Beds higher than 45 cm constructed of flexible materials as such galvanized iron sheets or flattened bamboo sheets (san-san or tad-tad) will require support posts because they lack rigidity.

4.5.5 Preparing a permanent raised bed

a) Making the walls − Cut open a 10-cm diameter bamboo pole along its length and flatten it to form

a bamboo strip (san-san or tad-tad). (See Figure 4.3). − Repeat the process until there are enough pieces of san-san or tad-tad to make

22 metres of 30-cm high fence. (A 10-cm diameter pole gives a 30-cm wide strip).

Figure 4.3 Making the bamboo walls

b) Setting the borders for the Permanent Raised Bed

− Decide on the orientation of the various beds based on para. 4.5.4 (a) above.

− Measure out a 10 x 1 metre oblong on the ground. − Hammer in stout 60-cm long pegs into the ground at each corner leaving

35 cm above the ground. − Add additional pegs as needed between the four corner pegs, keeping them

in straight lines between the corner pegs. − Securely attach the flattened bamboo wall panels to the pegs. − See Figure 4.4 for an impression of the finished framework. − Prepare the soil (see 4.5.5 (c) and fill the framework to a depth of 35 cms.

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Figure 4.4 The finished framework of a permanent raised bed

c) Soil Preparation

Raised beds can be used on a wide range of soils because they have good drainage. Sandy loam soils are the best for raised beds as they are less susceptible to waterlogging.

− A clay loam soil can be produced by mixing one part of heavy clay soil with one part compost or peat soil and one part coarse sand.

− For sandy soils, add more compost to increase the soil’s water-holding capacity.

− Avoid working the soil when it is wet as this can damage the soil structure. − Dig and loosen the soil as deep as possible. − Mixing in a small amount of soil used to fill the bed with the existing soil

avoids problems that arise from having layers of soil of different textures. − Apply 0.5 kg of Complete fertilizer to each 1 x 10 metre bed.

Dangers of using composted manures. Manure is high in soluble salts, which act to inhibit water uptake by plants, causing wilting and even foliar burn in extreme cases. Thoroughly water the soil mix to leach excess salts. A good soaking rain will do. This practice is especially important if plastic mulch is to be used as the beds become "leach-proof" once the plastic mulch is applied.

4.5.6 Preparing a crowned bed

A crowned bed has the center of the bed about 15 cm higher than the edges, to shed surplus water during heavy rain (see Figure 4.5).

To prepare a crowned bed:

− Drag soil towards the middle of the beds to form a ridge or crown along the length of the bed.

− Reduce the height of the crown by pushing the soil back towards the edges to form a uniformly curved surface 10-15 cm higher in the middle than at the edges.

− Wet the beds thoroughly to compress the soil surface. Several applications may be needed if the soil surface has previously dried out reducing the infiltration. The soil is sufficiently compacted if it resists forming a depression when an open hand is pressed down on the surface.

− Cover the surface with a 10 cm deep layer of mulch using either cut grass or leaves of Flemingia, Rinsonii etc.

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Figure 4.5 A crowned permanent raised bed

4.5.7 Further actions to improve the site for permanent raised beds

The following actions may be needed to improve the site of the raised beds:

a) Divert run-off away from the site Divert run-off water away from the beds with ditches (e.g. in minor valleys). Action: If possible dig a large storage pond to water the vegetables during dry

periods and stock it with fish.

b) Avoid shade Trees compete with the vegetable garden for nutrients and water as well as sunlight. Action: Locate permanent beds away from trees on sites that receive at least half

a day of full sun.

c) Reduce windspeeds Hot, dry winds increase water use by plants and may dry out foliage. Action: Plant a windbreak of shrubs to lower wind speeds and reduce plant

stress. This can lead to earlier and increased yields.

d) Provide supplementary water Due to the extra height above the ground, raised beds tend to dry out more quickly. Provide supplementary watering or, if not available, mulch the beds well to minimise evaporation of moisture from the soil surface. Action: Locate the garden near a water source and/or mulch the beds.

e) Break up raindrop impact on flowers Large raindrops typical of tropical storms can damage, and even break off, the flowers of some high value vegetable crops such as tomatoes. Action: Erect a bamboo frame over the particular beds and cover it with sheets of

plastic mosquito screening (see Figure 4.6). This converts raindrops into a fine spray which does minimal damage to the flowers.

Figure 4.6 Using mosquito screening to reduce raindrop impact on flowers

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4.5.8 Environmental issues

There are a number of problems associated with promoting organic farming in the acidic, inherently infertile soils of the uplands in the humid tropics:

− Fertilisers can be replaced by manures and composts in exceptional cases only. There are just not enough nutrients in the available organic matter to sustain a vigorous crop vegetation. For example, 10 tons of Ipil ipil cuttings are needed to apply the equivalent of 100 kg of nitrogen to the crop. This amount of material is simply not available to the average farmer.

− The very few economically viable systems of permanent upland farming that exist are found on very fertile alluvial or volcanic soils.

− Organic fertilizers are low quality fertilizers but, by improving soil structure and soil water-holding capacity, make applications of inorganic fertilizer more effective on sandy soils.

− Upland farmers need familiarizing with the circumstances when composts and manures, inorganic fertilizers or combinations of the two can be applied most beneficially. In particular, they should realize that to be effective on the mainly inherently infertile upland soils, between 12-30 t/ha/yr of organic fertilizers are needed ( i.e. 1.2 – 3.0 kg/m2/yr).

− Scarce amounts of manures and composts should be reserved for the intensive cultivation of vegetables on raised beds, in combination with inorganic fertilisers.

− If insufficient organic matter is supplied then the crops are mining the soil of any inherent fertility, and the system cannot be termed sustainable.

− Finally, it must be remembered that organic fertilizers brought in from outside the farm system are depleting areas elsewhere of nutrients. Probably the most eco-friendly organic fertilizer is bat guano, as the deposits falling onto the floor of dark caves, and accumulating year after year, are normally lost to recycling.

Finally, there is no pricing structure to pay upland farmers higher prices to compensate for the additional work used to produce organically grown fruits and vegetables.

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PART II

STEPS TO USING STOP The objective of the UDP is to arrest the environmental degradation in the uplands by changing the present farming system of annual corn-based cropping and root crops to one which is more appropriate with diversified cropping systems and perennial crops. The choice of conservation measures and land use options depends on the slope, soil type and soil depth.

Using Slope Treatment-Oriented Practices (STOP)

Step 1 Draw a “bird’s eye view” map of the whole farm. Step 2 Measure the slope using the Slope Indicator. Step 3 Determine the soil type and dig a hole and measure the depth to the “hard pan”. Step 4 Locate the appropriate conservation treatment and intensity of land-use on the STOP table. Note that with STOP, as slopes get steeper and soils become sandier:

− annual crops are replaced by agroforestry and forestry. − the spacing of cross-slope barriers gets closer. − on 45-55% slopes: plant tree crops in micro-basins, preferably using seeds,

to encourage a long taproot. No hedgerows needed. − only forest cover is to be developed from seed above 55%. Tap-rooted

species preferred.

Encourage the farmer to use an A-frame to lay out and plant appropriately spaced cross-slope barriers (hedges plus NVS) on the upper slopes and hilltops of his farm, and intensify and diversify annual crop production there.

On the steeper areas, start to replace corn and root crops by planting bananas and fruit trees such as mango, durian and lanzones.

Step 5 Fill in a land prescription form detailing the proposed crops and SWC measures for each land unit. If necessary, indicate the number of Napier grass or vetiver splits needed, and the expected incomes for different fruit trees and annual crops from the land unit. Step 6 Draw a second map showing the layout of the proposed SWC measures.

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STEP 1: MAP THE DISTRIBUTION OF LAND UNITS ON FARM

o Go to the highest point on the farm, if practical, and draw a “bird’s eye” view of

the whole farm (not an oblique view of one hectare). o Obvious changes, or breaks, in slope indicate a change from one land unit to

another. o Identify each land unit with a number on the map.

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STEP 2: MAKING AND USING THE SLOPE INDICATOR

STEP 2 a: MAKING THE SLOPE INDICATOR

o Photocopy the template for the Indicator onto a piece of acetate. o Laminate the acetate.

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STEP 2 b: USING THE SLOPE INDICATOR

The farmer must always accompany the BEW or AT to assess the land capability of the farm

1. THE SLOPE INDICATOR

The Slope Indicator is used to estimate the slopes appropriate for various land use options. It is an acetate sheet with a horizontal and a vertical axis. The angles shown on the horizontal axis indicate the maximum slope gradients for the conservation measures and soil types suitable for various land use options. It can help locate the least steep areas on the farm, as these have the best potential for arable cropping. A template is provided overleaf (Section 2).

USING THE SLOPE INDICATOR

Using the Slope Indicator

a) Attach a weight, e.g. a large paper clip or a ball pen, to a 30 cm long piece of string or thread. This is the plumb bob that ensures the Slope Indicator is level.

b) Clip the plumb bob securely to the Slope Indicator using a bulldog clamp or paper clip and position the plumb bob so it coincides with the vertical axis on the Slope Indicator.

c) Hold the Slope Indicator upright and tilt it until the string of the plumb bob exactly follows the vertical axis. The Slope Indicator is then level.

d) Keeping the Slope Indicator level, line it up along the farm slope. Note which lines on the Indicator the farm slope falls between. This is the approximate gradient of the land.

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STEP 3: DETERMINING SOIL TEXTURE IN THE FIELD

After determining the slope of the land, follow the instructions in the sheet titled Hand Tests to Determine Soil Texture in the Field to identify the soil type on the land. For each major change in slope you should check whether there has been a change in soil texture.

The objective is to try to avoid using sandy and sandy loam soils for arable crops, because their poor water retention capacity means they tend to suffer from severe moisture stress, even during the rainy season. Sandy soils are also much more sensitive to erosion than clay soils.

TTO DETERMINE SOIL TEXTURE IN THE FIELD

The extent to which moist soil can be shaped by the hand is indicative of its texture.

METHOD • Pick up a handful of soil (without stones) from the slope.

• Slowly drip water on to the soil and mix it well into the soil until it starts to stick to the hand. If water is not available use saliva.

• Form the sample according to each picture below until the next one is no longer possible: 1) The soil remains loose and single grained and can only be heaped into a pyramid: SAND (1) 2) The soil contains sufficient silt and clay to become cohesive and can be shaped into a ball that easily falls apart: LOAMY SAND (2) 3) The soil can be rolled into a short thick cylinder: SILT LOAM (3)

4) The soil can be rolled into a cylinder about 15 cm long:

LOAM (4) 5) The soil can be bent into a U:

CLAY LOAM (5)

6) The soil can be bent into a circle that shows cracks:

LIGHT CLAY (6) 7) The soil can be bent into a circle without showing cracks:

HEAVY CLAY (7)

Note: Texture classes (1) to (4) are sandy to silty soils and generally have good infiltration. Texture classes (5) to (7) are clayey soils that have generally poor infiltration but have a higher potential for arable agriculture.

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NOTES ON THE CHARACTERISTICS OF DRY SOILS WHEN DRY: o Loam or Silt will give off fine powdery dust if scratched or

blown upon, but - o Clay soil will not. o A Silt is extremely powdery because of its very low clay

content. WHEN WET: o A Loam feels soapy and more-or-less plastic. When rubbed

between the fingers until dry it leaves dust on the skin. o Clay does not.

o When augered, a Clay that has a slightly moist condition

displays shining faces. o A Loam does not.

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STEP 4: SLOPE TREATMENT-ORIENTED PRACTICES FOR STEEP LANDS (STOP) MODIFIED March 2006

OBJECTIVE: To produce a series of outward sloping bench terraces with a minimum soil depth of 50 cm at the back of the terrace.

Max. slope

Min. soil depth

Sandy – Loam soils Clay loam– Clay soils

(%) (cm) Soil and Water Conservation treatments

Maximum intensity of land-use between NVS/ hedgerows

Soil and Water Conservation treatments

Maximum intensity of land-use between NVS/ hedgerows

12% 50 cm Contour cultivation Any. Fallow with forage peanut. Contour cultivation. Any. Fallow with forage peanut 25% 100 cm* Contour hedgerows or lines

of Vetiver or Napier grass with 2-m wide NVS and 3-m wide cultivable strip² Contour cultivation³.

Relay planting with rice/maize-root crops-beans-peanuts to suppress weeds.

Contour hedgerows or lines of Vetiver or Napier grass with 2-m wide NVS and 3-4m wide cultivable strip². Contour ploughing to form terraces ³.

Rotations of corn, root crops and legumes. Relay planting of rice or corn-root crops-beans-peanuts to suppress weeds.

35% 100 cm No hedgerows. Vetiver or Napier grass lines with 2-m wide NVS, and 2.5 m wide cultivable strip)². Zero tillage. Heavy mulching.

Gradually replace maize and root crops with fruit trees planted among close cover crops and semi-perennials.

Vetiver or Napier grass lines with 2-m wide NVS and 3 m wide cultivable strip². Contour ploughing to form terraces ³. Mulching.

Rotations of corn and legumes. Relay planting of rice or corn-beans-peanuts to suppress weeds.

45% 100 cm No hedgerows. Vetiver or Napier lines with 2-m wide NVS. And 2-m wide cultivable strip². Zero tillage, Heavy mulching

Replace maize and root crops with agroforestry model of semi-perennials and fruit trees. No cultivation of beans and peanuts after 3 years.

Vetiver or Napier grass lines with 2-m wide NVS and 3 m wide cultivable strip². Contour ploughing to form terraces³. Heavy mulching

As above. If ploughing is not possible, replace corn and root crops with agroforestry model of fruit trees planted among close cover crops and semi-perennials, over three years.

55% 100 cm No hedgerows. Grass cover. Direct seeding and mulching around young trees

No cultivation Tree crops and grass cover

Vetiver or Napier grass lines with 2-m wide NVS and 2 m wide cultivable strip². Contour ploughing to form terraces³. Heavy mulching

Agroforestry model of semi-perennials and fruit trees.

65% 50 cm Grass cover. Direct seeding and mulching of trees

No cultivation. Forest trees and grass only.

Grass cover. Direct seeding and heavy mulching of trees

No cultivation Tree crops and grass cover only.

>65% - None suitable. No cultivation. Forest trees and grass only

None suitable No cultivation. Forest trees and grass only

* A slope with 100 cm depth of soil will give a terrace with 50 cm depth of soil below the hedgerow at the spacing indicated. ² The indicated cultivated strip width is the maximum permissible for 100 cm depth of soil, if 50 cm soil is to remain at the back of the terrace ³Advisable to follow contour ploughing on slopes above 12% with a harrowing to obliterate furrows which, if not exactly on the contour, channel run-off to low points causing gullies

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STEP 5: FILL OUT THE LAND UNIT PRESCRIPTION FORMS STEP 5 (a): EXAMPLE OF A LAND UNIT PRESCRIPTION FORM SHOWING PROJECTED INPUTS FOR SWC

LAND UNIT INPUTS

LAND UNIT

Site factors Prescriptions / Recommendations Projected Inputs

1 * Shape+ Width m Length m Area: m2 (W x L)

RIDGE Convex 8 80 640

Slope: % Soil texture Soil depth (cm) Erosion: Stoniness: Land use:

13-25 Sandy clay loam 50 Carabao track Small stones Cogon

• Contoured leguminous hedgerows/Napier or Vetiver grass strips, using improved design for cross-slope barriers (Barrier of 0.5 m hedgerow + 1.7 m wide grass riser, and terrace of 3.8 m).

• Plant peanuts, munggo, beans, pineapples. Mulch well with cogon from side slopes.

Vetiver splits 1100 OR Napier splits# 2200 OR Fleming/Rinson 106m Pineapple suckers 180

2 * Shape+ Width m Length m Area: m2 (W x L)

CREST/Plateau Flat 50 70 3500

Slope: % Soil texture Soil depth (cm) Erosion: Stoniness: Land use:

0-12 Clay loam >60 Sheet None Bananas

• Contoured Napier grass or Vetiver grass barrier at plateau/side slope interface.

• Ring weed the existing fruit trees and mulch with cogon. (Note: Bananas, are recommended for planting on flat areas, as farmers will be prepared to cut them down should there be a need to open up land for corn cultivation in future. E.g. in 20 years time, when Vietnam and Thailand no longer have surplus rice to export).

Vetiver splits 500 OR Napier splits# 1000

3 * Shape+ Width m Length m Area: m2 (W x L)

RIDGE Convex 6 80 480

Slope: % Soil texture Soil depth (cm) Erosion: Stoniness: Land use:

13-25 Sandy clay >100 cm Sheet None Mango, banana

• Ring weed the existing fruit trees and mulch with cogon. • Apply 200 g complete fertilizer per tree. • Plant more trees in gaps as required.

2 kg Complete

4 * Shape+ Width m Length m Area: m2 (W x L)

SIDE SLOPE Convex 100 30 3000

Slope: % Soil texture Soil depth (cm) Erosion: Stoniness: Land use:

>55 Sandy clay >50 cm Sheet None Cogon

• Lay out triangular planting arrangement with spacing according to fruit trees to be planted).

• Cut cogon on slope and pile 30-40 cm deep in 300 cm diameter circles on planting area to kill the cogon rhizomes in the soil.

• After 5-6 weeks (provided it has rained) plant seeds of fruit trees in 30 cm diameter cleared area in middle of cogon mulch. Graft scions later.

Fruit seeds Scions

5 * Shape+ Width m Length m Area: m2 (W x L)

SIDE SLOPE Concave 60 40 2400

Slope: % Soil texture Soil depth (cm) Erosion: Stoniness: Land use:

46-55 Clay loam > 50 cm Sheet None Cogon

• Lay out triangular planting arrangement with spacing according to fruit trees to be planted).

• Cut cogon on slope and pile 30-40 cm deep in 300 cm diameter circles on planting area to kill the cogon rhizomes in the soil.

• Make 90 cm diameter eyebrow basins and plant seeds of required fruit trees, mulch with cogon, and graft scions later.

Banana suckers 240 OR Seeds Scions

# Napier needs double row of splits

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STEP 5 (b): EXAMPLE OF A LAND UNIT PRESCRIPTION FORM SHOWING PROJECTED INCOMES PER LAND UNIT

Land unit prescription form comparing incomes from bananas and fruits with corn

LAND UNIT

Site factors Prescriptions / Recommendations Projected yields/ incomes

1 * UPPER SLOPE Shape+ Straight Width 20 m Length 40 m Area: (W x L) 800 m2

Slope: >70 % Soil texture: Clay loam Soil depth: cm Erosion: Rill Stoniness: None Land use: Corn

TOO STEEP FOR PROJECT INPUTS, BUT ADVISE FARMER TO: • REPLACE CORN WITH BANANAS AT 3 METRE SPACING

(Triangular layout) FOR REGULAR MEDIUM TERM INCOME. TREES WILL NEED TO BE PROPPED UP WITH BAMBOO.

• PLANT SMALL-CROWNED TREES (to minimise risk of toppling at maturity) E.G. COFFEE, LANZONES, RAMBUTAN ETC FROM SEED (in case bananas affected by bunchy top virus at later stage). ALIGN IN EAST-WEST DIRECTION.

• TRAIN FARMER IN GRAFTING ON SUITABLE SCIONS.

1.6 t/ha of corn twice/yr =3.2 t/ha/yr = 3.2 kg/10 m2 @ P14/kg = P45_______________ 1 hill banana/10 m2 yields 30 kg @ P4/kg = P120/yr_______________ Income from Land Unit 1 CORN: 800/10 * P45 = P3,600 BANANAS: 800/10 * P120 = P9,600 LANSONES: 800/10 * P186 =P14,880 (see below)

2 * RIDGE Shape+ Convex Width 15 m Length 35 m Area: (W x L) 525 m2

Slope: >70 % Soil texture: Clay loam Soil depth: cm Erosion: Stoniness: Land use: A few fruit trees

AS ABOVE. 156 Lansones/ha yielding 40 kg/tree after 8 years @ P30/kg = P186/10 m2/yr Income from Land Unit 2 CORN: 525/10 * P45 = P2,362.50 BANANAS: 525/10 * P120 = P6,300 LANSONES: 525/10 * P186 =P9,765

3 * MID-SLOPE (a) Shape+ Concave Width 40 m Length 30 m Area: (W x L) 1200 m2

Slope: 35-45 % Soil texture: Clay loam Soil depth: cm Erosion: Stoniness: Land use: Corn with a few mango trees

• PLANT MANGO AND DURIAN SEEDLINGS OR SEEDS AT 10 m SPACING (triangular layout) IN 1.5 M DIAMETER MICRO-BASINS, ALIGNED IN EAST-WEST DIRECTION.

• HEAVILY MULCH MICRO-BASINS. • APPLY COMPLETE FERTILISER AT RECOMMENDED

RATES WITH ANNUAL INCREMENTS. • INTERPLANT WITH BANANAS TO GET EARLY INCOME.

8 year-old Mango yields 100 kg/tree or 10 kg/ 10m2 @ P12/kg = P120/ 10m2.________ Income from Land Unit 3 CORN: 1,200/10 * P45 = P5,400 BANANAS: 1,200/10 * P120 = P14,400 LANSONES: 1,200/10 * P186 =P22,320 MANGOES: 1,200/10 x P120 =P14,400

4 * MID-SLOPE (b) Shape+ Straight Width 15 m Length 20 m Area: (W x L) 300 m2

Slope: 35-45 % Soil texture: Clay loam Soil depth: cm Erosion: Land slippage at lower end Stoniness: None Land use: Corn

AS ABOVE. Income from Land Unit 4 CORN: P1,350/yr BANANAS: P3,600 @ 1.5years LANSONES: P5,580 @ 8 years MANGOES: P3,600 @ 8 years

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STEP 5 (c): BLANK LAND UNIT PRESCRIPTION FORM

Province:

Mun.

Brgy:

Sitio:

Farmer name: Ann. food requirements: Corn: sacks kg Family size: Vegetables: sacks kg Farm area: Roots: sacks kg Land tenure: : Fruits: sacks kg

LAND UNIT

Site factors Prescriptions / Recommendations Projected yields/ incomes

1 * Shape+ Width m Length m Area: (W x L)

Slope: % Soil texture Soil depth:cm Erosion: Stoniness: Land use:

2 * Shape+ Width m Length m Area: (W x L)

Slope: % Soil texture Soil depth:cm Erosion: Stoniness: Land use:

3 * Shape+ Width m Length m Area: (W x L)

Slope: % Soil texture Soil depth:cm Erosion: Stoniness: Land use:

4 * Shape+ Width m Length m Area: (W x L)

Slope: % Soil texture Soil depth:cm Erosion: Stoniness: Land use:

* Describe as Crest, Ridge, Spur, Upper Slope, Mid-slope, Foot slope, Minor valley + Describe as: Convex, Concave, Straight or Compound (i.e. Concavo-Convex)

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STEP 5 (c) (cont’d): BLANK LAND UNIT PRESCRIPTION FORM

LAND UNIT

Site Factors Prescriptions / Recommendations Projected yields/ incomes

5 * Shape+ Width m Length m Area: (W x L)

Slope: % Soil texture Soil depth:cm Erosion: Stoniness: Land use:

6 * Shape+ Width m Length m Area: (W x L)

Slope: % Soil texture Soil depth:cm Erosion: Stoniness: Land use:

7 * Shape+ Width m Length m Area: (W x L)

Slope: % Soil texture Soil depth:cm Erosion: Stoniness: Land use:

8 * Shape+ Width m Length m Area: (W x L)

Slope: % Soil texture Soil depth:cm Erosion: Stoniness: Land use:

UDP Technician:______________________________ Signature:____________________________________

Cooperator: ________________________________ Signature ___________________________________

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STEP 6: PREPARE MAP SHOWING LAYOUT OF SWC MEASURES

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ANNEX I

THE EFFECT OF POOR HEDGEROW LAYOUT ON EROSION AND FARM PRODUCTIVITY

1. BACKGROUND UDP’s objectives include developing a replicable model for sustainable management of the natural resources in the uplands of five provinces of Region XI (Mindanao). With the disappearance of much of the natural forest cover the upland soils and water remain as the two most important remaining natural resources in the uplands. Upland soils are highly sensitive to disturbance and low in resilience, and their use for agriculture is precipitating or accelerating land degradation16. UDP surveys have verified previous estimates of soil erosion of 360-400 tons of soil/ha/year, which translates into reductions in the depths of soil profiles of 50-100 cm over the last 20 to 30 years17, 18. The basic fact is that as the slope becomes steeper, the risk of erosion increases relentlessly, making soil conservation interventions expensive, in terms of labour, and unreliable. 2. RATIONALE Contour hedgerow intercropping with annual crops has been given special prominence in the Philippines as a cheap way to control erosion on sloping land. Alternatives to hedgerows of leguminous shrubs such as Flemingia and Rinsonii, include planting single lines of clumps of lemon grass, guinea grass or Napier grass across the slope. A simpler technique uses 0.5 metre-wide uncultivated Natural Vegetative Strips (NVS) across the slope to slow down run-off and filter out eroded soil. A combination of soil loosening in the alleys by cultivation, particularly by ploughing, and water erosion, moves soil directly down slope to be intercepted by the hedgerow plants. The build up in soil behind the hedgerows reduces the slope between hedgerows. Observations made during a series of UDP soil and water conservation consultancies since 2003 support the view that cross-slope barriers (i.e. hedgerows and NVS) are inappropriate when applied on slopes steeper that 25% (e.g. Young 198919; Hudson 199220 p.102). The combination of contour cultivation and soil erosion behind hedgerows and NVS leads to the formation of outwardly sloping terraces. These are unable to prevent a build up in volume and velocity of run-off during heavy rainstorms. The appropriate way to control erosion on sloping land in the humid tropics is with reverse-sloped terraces21 to divert and discharge run-off into waterways.

16 ACIAR (2000) Soil Conservation Technologies for Smallholder Farming Systems in the Philippine Uplands: a Socioeconomic Evaluation. Australian Centre for International Agricultural Research, Cranberra, 2000, (ed. R A Cramb) 17 Proud, KRS (2004). The reduction in soil depths of upland soils of Southern Mindanao, their causes and consequences. Report for the Upland Development Programme by K R S Proud (Upland Farming Systems/Soil & Water Conservation Consultant), 16 October 2004 18 Proud, KRS & Viloria, BH (2004). Problems with Cassava production in the uplands of Southern Mindanao. Report for the Upland Development Programme by K R S Proud (Upland Farming Systems/Soil & Water Conservation Consultant), and Ben-Hur Viloria (Sustainable Agriculture Development Coordinator). 25 October 2004 19 Young, A (1989). Agroforestry for soil conservation. Wallingford UK, CAB International 20 Hudson, N (1992). Land husbandry. London. Batsford * VI = the vertical fall between adjacent hedgerows 21 FAO (1988). Watershed management field manual Slope treatment measures and practices. FAO Conservation Guide 13/3

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While impressive amounts of soil have been held back by the hedgerows and NVS, it appears that poor hedgerow layout and choice of species is reducing the agricultural productivity of the land. 3. OBSERVATIONS 3.1 Poor layout of hedgerows and NVS can be traced to the following:

− It is not possible to establish accurate contour lines+ across steep slopes using the carabou’s back method, or the human eye. Attempts to do so produce mis-aligned hedgerows with low points that channel and concentrate run-off - increasing the risk gulley formation. (+ Every point on a contour line has the same elevation).

− “Enriching” the NVS with root crops results in damage to the protective soil conservation functions of the NVS when the roots and tubers are harvested. The primary function of NVS is to form a permanent barrier to slow down run-off. Any secondary uses should only be recommended provided they don’t adversely affect the primary function.

− Because SALT hedgerows and NVS are by nature permeable barriers, which only slow down and filter run-off, the conventional Vertical Interval (VI)* formula is not an appropriate method for spacing cross-slope barriers. The VI is normally used to design terrace systems that store all the run-off or divert it into a safe disposal area23. The practice of using a VI (usually 1.5 m – the eye height of a farmer) places the hedgerows too far apart. The distance between permeable or filter hedgerows should be based on soil depth, slope and cultivation requirements7.

3.2 Poor layout and management of hedgerows and NVS on steep slopes reduces

productivity in the following ways (see Figs. 1-4):

− One consequence of wide spacing is an increase in height of the riser as soil erodes from the back of the terrace and accumulates at behind the barrier. E.g. on a 40% slope, each metre between hedges increases the height of the riser by 40 cm. In time a 5-m wide terrace will have a 2.0 m high riser resulting in 1.5-2.0 m depth of topsoil accumulating at the front of the terrace. Most of this depth of soil is unavailable to the shallow rooting systems of the annual crops grown. If the exposed sub soil at the back of the terrace is composed of coarse volcanic sands and gravels it may not have sufficient nutrients or soil moisture to support annual or perennial crops.

− The higher the riser the greater the energy of the run-off as it strikes the soil – increasing the chances of under-cutting the terrace, causing it to collapse, which takes land out of production.

− Exposed subsoil at the back of the terraces, due to the downhill movement of soil, is an indication the hedgerows are spaced too widely. This produces a gradient in fertility in which stunted crops are seen at the back of the terrace where the shallow soil is infertile, while plants grow more robustly immediately behind the hedgerows where there is an accumulation of eroded topsoil and more soil moisture.

− In very heavy rain the surface layer of top soil gets saturated rapidly and most of the water runs off. BUT if the top soil has been eroded away exposing a permeable substrate of gravels and coarse sand, then hundreds of tons of water can be absorbed into the hillside during extended rainfall, increasing the possibility of the

22 Hudson, N (1992). Land Husbandry. Batsford Ltd., London. (p 98)

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terraces slumping and causing a land slide. Examples of very permeable subsoils of gravels and coarse sands can be seen exposed behind hedgerows in Meliina, Tampakan. Just 30-40 cm of topsoil remain before deep deposits of unproductive lahar become exposed at Tapicong, South Cotabato. Skeleton soils, formed by the washing out fine and fertile silt and clay particles, have no potential for agriculture or forestry.

− Cutting into the base of terraces formed by NVS with the plough, to create an extra row for planting, threatens the stability of any trees planted earlier on the NVS. As the trees have little or no soil for root growth on the down hill side they are likely to fall over when large crowns have developed.

− The vertical riser, produced when the farmer ploughs or cuts into the NVS or ground close to the base of the hedgerow during cultivation, results in a wall of bare soil. The amount of soil moisture stored in the terrace for use by the crops may be reduced when the riser is exposed to drying out by wind and sun. It can also make the terraces more susceptible to erosion.

FIGURES 1-4: THE STAGES IN TERRACE FORMATION ON WIDELY SPACED HEDGEROWS

Fig. 1. Corn growing between widely spaced hedgerows. Slight movement of soil forwards

Fig. 2. Terrace formation visible. Shallower soil at back of terrace affecting crop growth

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Fig. 3. Terrace formation is obvious but crops at back of terrace are

stunted due to growing in infertile subsoil

Fig. 4. High, unstable terraces formed. Crops growing in exposed subsoil at back of terrace are stunted with low productivity

3.3 The plant species used, and the way they are planted also affects their

effectiveness:

− Crops such as pineapples, cassava and sugar cane, are not suitable for forming hedgerows. When these crops are harvested or replaced the partially formed terraces of eroded soil they held back become unprotected “waterfalls” in heavy rain. The erosive energy of run-off increases by flowing over these semi-terraces. Hedgerows and NVS are meant to form permanent features of the landscape, so the plants used to form them should also be of a permanent nature.

− 15-30 cm gaps left between individual clumps of lemon grass, Guinea grass, Napier grass, planted across the slope in single lines as hedgerows, reduces the effectiveness of the hedgerow in slowing down run-off. Although eroded soil is deposited behind the clumps, the gaps concentrate and accelerate the flow of run-off carrying the fertile finer silt and clay soil particles with it during heavy storms.

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− The SALT recommendations for using leguminous species such as Flemingia and Rinsonii are a double hedgerow (50 cm between each row) planted with seeds at 2 cm intervals. The terrace areas between hedgerows are 3-m wide. When insufficient seeds were supplied, farmers “economised” by planting widely-spaced single hedgerows with 15 cm or more between the seeds.

− Leguminous hedgerows are not suitable for soil conservation on steep slopes. Although they hold back stones and gravel, they are unable to provide the fine filter needed to hold back very silt and clay soil particles. Such hedgerows can lead to the formation of unstable terraces, where rows of thin plant stems 1-2 cm wide, hold back several tons of stony soil ,creating a land slide hazard.

4. STRATEGY 4.1 UDP actions under STOP The development of Slope Treatment-Oriented Practices attempts to rectify the short-comings mentioned above. For example:

− Basing the distance between permeable or filter hedgerows on soil depth, slope and cultivation requirements. Restricting the use of hedgerows for annual crops to soils at least 100 cm deep on hill tops and upper slope land units, where volumes and velocities of run-off, and hence the erosion hazard, are lower. Terrace formation should result in 50 cm depth of soil at the back of the terrace.

− Using the A-frame to align the hedgerows accurately along contours.

− Minimising exposure of the bare soil in the riser by incorporating a 2-m wide NVS below the hedgerow to break up the height of the riser into two sections. This also deflects the energy of run-off passing through the hedgerows away from the base of the riser. Bananas planted in the NVS do not damage its primary function of soil conservation.

− Doubling the rows of Napier, guinea and lemon grasses by planting a second row of clumps row aligned with the gaps in the first row. (Vetiver grass is the most effective grass to use as a cross-slope barrier as its tillering forms a dense barrier, so only a single row is needed with splits planted 10-15 cm apart. Its roots go downwards – not sideways, and it dies back in the dry season).

− Substituting corn with fruit trees on the long slopes. Hedgerows are not needed if the land is to be used for perennial crops.

Research is needed to quantify the extent to which improper hedgerow layout is affecting production to argue for changes in policy, should the need arise. For example, the DA is advocating hedgerows be established on the long, very steep slopes in the mountains of Benguet Province.