AgroforestrySystems 24: 247--269, 1993. �9 1993 Kluwer Academic Publishers. Printed in the Netherlands.

Alley cropping and analog forests for soil conservation in the dry uplands of Sri Lanka

I. K. NUBERG and D. G. EVANS School of Environmental Planning, University of Melbourne, Parkville, Victoria 3052, Australia

Key words: agroforestry, alley cropping, human ecology, home gardens, soil conservation, Sri Lanka, uplands

Abstract. The use of contour hedgerows of woody legumes to control soil erosion has been promoted amongst smallholders in the Upper Mahaweli catchment of Sri Lanka since 1988. The success of this program depends greatly on the properties of the different production systems occupying the alleys created by these hedgerows such as: profitability, time taken for profit to be realized, labour requirements, seasonal distribution of labour, environmental and economic stability, biophysical sustainability, the contribution of the system to the domestic needs of the farm family, adoptability of the system and successful management of the hedgerows. These properties were used to evaluate seven desktop farm models with different combinations of: seasonal crops, coffee-pepper intercrop, fodder-dairy, woodlot, and analog forest established in the alleys. The analog forest is a perennial polyculture which, like the traditional forest garden, is structurally and functionally analogous to the natural forest. It was found that a model with 40% seasonal crops, 20% perennial crops (coffee-pepper) and 40% analog forest made the best compromise between the properties under consideration. It is recognized that the socio-economic conditions that determine the appropriateness of this model in the Sri Lankan context are not universal and the extension of the analog forest concept into other tropical uplands is discussed.

Introduction

Alley cropping in Sri Lanka

Alley cropping has been accepted as an appropriate agroforestry technology for smallholder farmers throughout the ecologically marginal areas of Sri Lanka [Nanayakkara, 1991]. Research into alley cropping was first applied in the dry low country in the north of the island [Newman, 1985; Weerakoon and Seneviratne, 1984] and later in the uplands [Gunasena and Hitinayake, 1990]. Since 1988 the Mahaweli Authority of Sri Lanka has been working jointly with GTZ, the German Agency for Technical Cooperation, to estab- lish its practice on the steep slopes of the upper catchment of the Mahaweli River [Mohns and Rajapakse, 1990]. Soil erosion is a serious problem in this area not only in terms of the sustainability of upland agriculture but also because of the threat from sediment on the longevity of Sri Lanka's principal hydroelectric and irrigation reservoirs which are on this river [TAMS, 1980].

The particular form of alley cropping followed in this area is the package called SALT (from Sloping Agricultural Land Technology) which was devel-

248

oped in the Philippines [Tacio, 1991, 1992]. Many land management agen- cies in Sri Lanka enthusiastically endorse it. It is based on a framework of alleys created by hedgerows of nitrogen-fixing woody species planted along the contour. It is characterized by a sequence of two alleys of seasonal crops and one alley of perennial crops that is repeated up the slope. Other variants have been developed where a block of alleys is dedicated to fodder produc- tion for a livestock system or to a woodlot system. The emphasis is on persuading farmers to maintain a perennial vegetative cover on as much of the land as possible.

The success of this program depends greatly on the relative profitability of different production systems, and, most importantly, the payback period. Farmers in this situation typically hold a very high discount rate on future profitability [Hosier, 1989]. Their immediate concerns are so pressing that they prefer to cultivate seasonal crops such as vegetable s and tobacco. They can only adopt perennial systems with technical assistance and subsidies, and currently a coffee/pepper intercrop is the system most widely being pro- moted. However, this has been very disappointing due to the steady decline in coffee and pepper prices in recent years (e.g. the producer prices for coffee and pepper in 1986 were 53 and 93 Rs/kg, respectively, but by 1990 they had fallen to 24 and 59 Rs/kg).

The cultivation of seasonal crops is the most certain way to fulfil imme- diate financial needs. However, personal needs such as domestic nutrition and autonomy, and communal needs such as soil conservation and regional biodiversity, remain unfulfilled [Nuberg et al., 1994]. Furthermore, if the coffee/pepper intercrop fails as a reliable source of income, it is unlikely to be maintained, and any soil conservation value of the cropping system will be lost. It seems necessary to devise a farm model that meets immediate needs while at the same time fulfilling longer term social and environmental objectives.

Analog forestry

One possibility to achieve this is to use cropping systems that mimic the structure and successional processes of a tropical forest. Seasonal crops (pioneer species) are interplanted with a variety of perennials (climax species) which come into production as they shade out the seasonal crops. Although this idea is not new [Holdridge, 1959], it has developed consider- ably over the last decade. Hart [1980, 1982] advanced what he called the analog hypothesis: that

. . . the agricultural viability [which he assumes to include biological, economic and social viability] of a particular crop sytem is directly related to the structural and functional similarity between the crop system and a natural plant system in the same environment [Hart, 1982, p. 79].

The analog concept, if not the term, is well represented in the corpus of agro-

249

ecological thought, especially the research into traditional agroecosystems [Altieri, 1987; Altieri et al., 1983; Ewel, 1986; Gliessman, 1990].

In Sri Lanka the concept is embodied in the term Analog Forest coined by Senanayake [1987]. He particularly recognized the potential of the analog forest for the conservation of wild flora and fauna in the face of habitat destruction, but it can also provide a salubrious habitat for humans. The traditional forest gardens of Sri Lanka are, to an extent, analog forests. They provide a wide range of domestic goods and services as well as produce for sale, and there is wide currency to the idea of using them as a model for mixed cropping lBavappa and Jacob, 1981, 1982; Bavappa et al., 1986].

Aim and method

The aim of this paper is to assess possible farm models, some including an analog forest component, that could be practically implemented within the context of a program of alley cropping for soil conservation. The method employed is first to calculate the net financial returns over ten and twenty year periods and the labour requirements of the candidate models. The results from this exercise are then incorporated in a broader evaluation of the stability, biophysical sustainability, and relevant social properties engendered by their component production systems. This is based on the authors' belief that consideration of financial, environmental and social properties should be made concurrently for the effective evaluation of agroforestry technology.

While the results are specific to the Upper Mahaweli catchment of Sri Lanka, the evaluation of system properties undertaken in this paper should be of methodological interest to agroforestry researchers anywhere in the tropics. Some generalized comments can be made on the relevance of the analog forest in other areas of tropical uplands.

A modelling experiment

The study area

Sri Lanka is divided broadly into three climatic zones, the Wet Zone (2300-- 5000 ram/y), the Intermediate Zone (1500--2300 ram/y) and the Dry Zone (< 1500 ram/y). The upper catchment of the Mahaweli River falls in the first two zones. The area selected for study is the rainfed slopes of the Inter- mediate Zone of this catchment (elevation 800--1500 m.a.s.1.), which is representative of many problematic upland regions found throughout the tropics. The rainfall here is bimodal, with the greater peak occurring from October to January and a smaller and less reliable fall from March to May.

The predominant soils in the area are red-yellow podzols, reddish-brown latosols and immature brown loams with moderate to high erodibility. The topography, which varies from rolling hills to steeply dissected mountains, ensures that soil erosion will be a serious problem to any exposed soil.

250

The density of the two million people living in the uplands ranges from 570 persons/km 2 in Kandy district to 270 persons/km 2 in Badulla district. In terms of area, the largest single farming system in the region is estate- managed tea. However the most common smallholder farming systems are the 'Kandyan Forest Garden' with paddy cultivation [Jacob and Alles, 1987], and permanent rainfed seasonal cropping (vegetables and tobacco) which has recently evolved from shifting cultivation. Generally, the forest gardens and paddy are for subsistence production while seasonal cropping is for commer- cial production. Markets for vegetables are serviced by private merchants while tobacco is marketed through a central company.

The models

Essentially, five production systems are arrayed in combinations along the SALT format to form seven farm models. The general model size is 0.5 hectare. It is divided into 15 alleys of 4 metres width created by 0.5 metre wide double hedgerows of Gliricidia sepium planted at close spacings (15-- 20 cm) along the contour. Each alley has a cropping area of about 300 m 2. Figure 1 illustrates how the models may appear.

The first three models are variants of the SALT package from the Philippines. The coffee/pepper intercrop is well established in Sri Lanka and the small scale stall-fed dairy systems and woodlots have been promoted at various times and places throughout the uplands. The next three have

ND OW

ALLEY ISO~f-/fZ,/Ti.'~ ~ r ~ , . _ =oPs

Fig. 1. The seven 0.5 ha farm models showing the allocation of the five production systems. Each model has 15 alleys created by contour hedgerows.

251

different proportions of analog forest combined with the basic SALT package. In the seventh model only seasonal crops are grown in the alleys. Exclusive cultivation of seasonal crops is the cropping pattern currently preferred by farmers in this area. The characteristics of each of these component production systems of the models and the reasons for their choice are described below.

The component production systems of the models

Seasonal crops The seasonal cropping sequence used here reflects that which is most likely to be followed by farmers desiring to maximize their immediate financial gains. These are mainly vegetables, but also subsidiary food crops (pulses and grains), that offer quick and lucrative returns on investment for the small- holder. The suite of vegetable crops chosen for the model, ie beans, carrot, cabbage and chilli, was chosen from observation and local publications [Sri Lankan Department of Agriculture, 1990]. Though not typically followed in the area, commercial crops of gingelly and green gram could be sown after the April rains, and have therefore been included in this model. For the sake of analysis this crop pattern is iterated every year without change. In reality there may be considerable variation in crops planted and net returns received from year to year.

Seasonal crops are also intercropped with all other systems except the dairy-fodder system for the first two years. This is to take advantage of all available growing space. In these cases the yields per unit area of these seasonal crops are assumed to be 60% and 40% of the monoculture crop for the first and second year, respectively.

The data for yields and labour requirements were derived by averaging the results of surveys of rainfed crops, principally in the Badulla district, by the Department of Agriculture [Sri Lankan Department of Agriculture, 1980-- 1990].

Coffee~Pepper intercrop This is a proven export crop mix that is widely promoted by the Sri Lankan Department of Export Agriculture (DEA). Yields were calculated at spacings of coffee at 3 • 3 m intercropped with pepper at 3 X 3 m. Yield functions, harvest efficiency and labour requirements were derived from data collected by DEA (M. de Silva, pers. comm.) and their publications [Bavappa et al., 1986]. As prices received for these commodities have fallen greatly in recent years (see 'Introduction') the average producer price from 1986 to 1990 was used in calculations.

Dairy~Fodder The dairy system used here is of 1.5 livestock units (1 cow and 1 calf), stall- fed and sustained by 0.2 ha of well maintained Guinea grass (Panicum maxicum ecotype A) grown in alleys, and up to 1300 m of Gliricidia sepium

252

hedgerow. Half of the grassed alleys are recultivated every third and fourth year. This production alternative has been chosen because of the soil conservation value of the fodder alleys and the incentive that the farmer has to maintain the hedgerows. Assuming the farmer has appropriate training, fodder production can be maintained so that the average milk yield (over the whole lactation) will be 8 litres/day. All production data for this system was derived from information supplied by the Mid-Country Livestock Develop- ment Centre, Mahaberiyatenna.

Woodlot This system features 0.2 ha of Eucalyptus spp. trees at a staggered spacing of 3 X 4 m. Seasonal crops are grown between the trees for the first two years after establishment. Poles are harvested in the sixth and tenth years and final harvest occurs in the twentieth year. Production data for this system was supplied by the Badulla Office of the Department of Forestry. This office has recently completed a five-year Community Forestry Project which established the popularity of private farmer woodlots, particularly using eucalyptus, over communal village woodlots. Fuelwood and timber shortages are chronic in the uplands, and woodlots help relieve pressure of illegal harvest of natural and plantation forests, and allow farmers to participate in a low input and potentially high return investment.

Analog forest This system is designed to yield a stable income spread throughout the year, an excellent control of soil erosion, improved microclimate for horticultural production and general living, and an opportunity for diverse domestic nutri- tion. Table 1 presents the species and the numbers required for a 0.5 ha analog forest that would be suitable for the Intermediate Zone uplands. It comprises species commonly grown in traditional forest gardens in that area.

Five layers are represented, viz: emergents; canopy; sub-canopy; shrub layer; and ground cover species. They are specifically arranged to fit into the 4.5 m alleys on a hillslope, creating some alleys with a more open canopy to provide micro-habitats for sun-loving species. The shrub layer (coffee and cardamon) form the regular backgrotmd matrix upon which the other species are placed.

Canopy and sub-canopy species are kept in separate and alternating alleys. This permits sub-canopy species to be partially covered by canopy from trees in adjoining alleys. In any sub-canopy alley the selection of species is limited to two (banana/lime; banana/orange) or three (cherimoya/karapincha/citrus) for ease and efficiency of management and harvest. Ground cover crops are kept to a few selected alleys for ease of management and harvesting. How- ever, within the alleys they are dispersed into many small (approx. 4 m 2) plots to avoid opening up the canopy too much.

Emergents such as kitul palm and eucalypt can grow through the canopy created by the other trees. Traditionally areca nut is often planted as a

253

Table 1. Species list of an 0.5 ha analog forest.

Forest layer Latin name English name Sinhala name Number in 0.5 ha

emergents Areca catechu Areca nut puwak 54 Eucalyptus sp. Eucalyptus 6 Caryota urens Fishtail palm kitul 15

canopy Persea americana Avocado aligata pere 16 Artocarpus incisa Breadfruit del 5 Mangifera indica Mango ambe 15 Elaeocarpus glandifuler Ceylon olive weralu 2 Carica papaya Papaw papol 18 Artocarpus integrifolia Jak fruit kos 2 Michelia champac -- sapn 7

sub-canopy Musa sapientum Banana kesel ghedi 30 Anona cherimolia Cherimoya anoda 9 Murraya koenigii Curry leaf tree karapincha 9 Citrus sinensis Orange dodan 20 Citrus aurantifolia Lime dehi 20

shrub Coffea arabica & robusta Coffee kopi 270 Elletaria cardamomum Cardamon enasal 280

ground cover Zingiber officinale Ginger inguru 18 plots of 4 m 2 Curcuma domestica Turmeric kaha 18 plots of 4 m 2 Dioscorea spp. Yam gahala 18 plots of 4 m 2 -- 'Arrowroot' hulankeriya 18 plots of 4 m 2

border species. This can have a useful visual function and makes it easier to harvest. Spacing of perennials is done with a vision of the final mature canopy spread of various species. The density is between that of a forest- garden and a monoculture orchard.

Production and labour data used for the analysis came from local horti- cultural extension literature, unpublished data from Agriculture Department research stations, and informal sources.

Evaluat ion procedure

The models were evaluated in two phases. First, the annual net returns, and the annual labour requirements and their seasonal distribution were calcu- lated. This was done using nested computer spreadsheets covering periods of ten years and twenty years (to include the woodlot system). All input costs and output prices used were 1990 annual averages, except for coffee/pepper prices as previously explained. The calculation of net returns required a good approximation of the average daily rate for agricultural labour in the area in 1990. Labour costs vary widely depending on locality, month, activity, and gender. The rate used was Rs 70 per labourday. Waged labour is only one

254

form of labour employed here. There are also family labour and labour exchange processes in which there is no money transaction, but for the purposes of this exercise the wage rate served as proxy for this labour.

Two additional treatments were devised for the calculation of annual net returns. These treatments modified the 'Seasonals Only' (SO) and the third 'Analog-forest-SALT' (AS3) models. Whereas the SO model assumed that there was no reduction in returns due to fertility loss, a 'Seasonals Decline' (SD) treatment was applied which assumed that productivity would be reduced by 10% over each ten year period due to fertility loss. The magni- tude of this reduction was based on work in the project area [Gunatilake, 1990]. The AS3 model was modified by establishing one third (i.e. five alleys) of the analog forest each year for the first three years of the model run. Those alleys not under analog forest during this time were cultivated for seasonal crops. This model is indicated as AS4. (The authors thank an anonymous reviewer for suggesting this treatment.)

The seasonal distribution of labour is represented by a Time Concentra- tion Index (TCI, ex. Jacob and Altes [1987]). This index is calculated as the square root of the sum of squares of the deviations of the monthly labour requirement in a particular year. As can be seen from this formula the TCI will be lower the more evenly spread labour is throughout the year.

TCI = .~[(dia ~ - Dyear) 2 q- (dfeb -- Dyear) 2 + . - - -Jr- (dnov - Dyear) 2 -1-

+ ( d d e c - - Oyear) 2]

where: dj~, dfeb, etc., are the labourday requirements for each month; and Dyea r is one twelfth of the total annual labourday requirement.

In the second phase of the evaluation, the results from the above analysis were incorporated in a discussion of broader social and environmental characteristics of the production system. The categories used for discussion were financial productivity; labour properties; economic and environmental stability; biophysical sustalnability; contribution to domestic needs; and the likelihood of adoption and successful maintenance of contour hedgerows. Thus this study is then loosely framed within the human ecology perspective on agricultural research which has been elaborated by Rambo [1982], Marten [1986] and others.

A complete copy of the production schedules and finer technical points of the model design, especially of the analog forest, is available directly from the principal author or in Nuberg [1992].

Results of modelling

A n n u a l net returns over the f irst ten years

Figure 2 shows the annual net returns, or financial productivity, for each of

255

(1) Q..

o "

30000

25000

20000

15000

10000

5000

/ / ~ As4

""" ~ . SO

" " " ~ ' * ~ S3

/ / 7 / ." n,~0.000, ,he .

o

5

-5000

-10000

-15000

-20000

"1 I I I I I I 6 7 8 0 10 11 12

Year

Fig. 2. Annual net returns of the seven models for the first twelve years, including additional treatments of two of the models (broken lines).

the models in the critical early years after establishment while Fig. 3 shows the annual labour requirements. The net returns of the seasonal cropping are shown for two assumptions, ie for no reduction in returns due to fertility loss (the full line, SO) and 10% reduction over ten years (the heavy broken line, SD). Even under these circumstances it would remain the most attractive alternative to many farmers. The great variety of curves in this chart reflects not only the growth in biological productivity but also the very different labour requirements of the different models.

The financial productivity of the SALT models ($1, $2, $3) never exceeds that of seasonal cropping, while the analog forest models (AS1, AS2, AS3, AS4) take till the seventh and eighth years for this to occur. The relative productivity of the models at system maturity is shown at the twelfth year. Although eventually very productive, the costs of establishment of the analog forest models are very high both in terms of materials and labour. Indeed, the complete analog forest model (AS3) runs at a loss until after the fourth year.

256

450

400

350

300

2 5 0

"~ 200

0 J:] ..J

150

100

50 t

~ = 81 -o S2

AS1

~ AS2 SO

I I I ' I I ' I I I I I 2 3 4 5 6 7 8 9 10 11

Y e a r

Fig. 3. Annual labour requirements of the seven models for the first ten years.

It may be possible to diffuse the heavy establishment costs and low early returns of the AS3 model by establishing it in stages. This is attempted in treatment AS4 (the light broken fine with crosses) where one third of analog forest is established each year for t!?e first three years. This treatment does not overcome the period of negative income; it just delays the problem (to years 3 and 4) as well as delaying maturity (at year 12).

Time horizons and discount rates

Table 2 ranks each model for Net Present Value over two time periods for four discount rates. It is assumed that the productivity of all perennial components, both in alley intercrops and analog forest, has reached its maximum by year ten (year 12 for AS4) and is constant thereafter. The first time period (years 1 to 10) reflects the degree to which early returns are

257

accrued. This is assumed to be the time horizon of most small farmers. The second period (years 1 to 20) reflects long term financial productivity and is assumed to be the time horizon of planners. Planners with a long term view should probably use discount rates between 0% and 5%, while businessmen might hold a 15% discount rate and farmers are likely to hold a 30% rate [Hosier, 1989]. The higher discount rates are used to simulate the preference for early over delayed income.

For the farmer, or a local businessman investing in market gardens, the financial rationality of remaining with exclusive seasonal cropping (SO) is clear, even if fertility decline is taken into consideration. The analog forest models offer no financial inducement. However, for the landuse planner, two of the analog forest models (AS1 and AS2), and even the seasonals/coffee/ pepper model ($1), perform financially well in the long term. If exclusive seasonal cropping could be carried out with no erosion or fertility loss, as implied by SO, then it is still a good financial option.

Although the AS4 treatment does not perform satisfactorily, its perform- ance relative to AS3 indicates the value of sequential establishment of the analog forest, especially when high discount rates are used. This information could be useful in the implementation of the AS1 and AS2 models.

Sensitivity testing of the models was made for a wide range ( -50% to +100%) of producer prices of export crops (coffee, pepper and cardamon) in the models; these tests were made at the four discount rates mentioned above. Generally, there were few shifts in the ranking of models given in Table 2. When a zero discount rate was applied, the SO model only became less profitable than the $1 and AS1 models when export crop prices were 60% and 65%, respectively, higher than the standard. At higher discount rates, progressively higher producer prices for export crops were necessary to maintain this ranking. Export crop prices below the standard only caused minor shifts in the ranking of AS2, $2 and $3 models.

Annual labour requirements

The labour input required for establishing all models is greater than the labour requirement in later years (see Fig. 3). This establishment labour includes that required for preparing the land, planting the contour hedge- rows, planting the perennial crops, and cultivating the seasonal crops, which include those crops interplanted with perennial seedlings for the first two years. The models with an analog forest component require the most labour for establishment, mainly because of the great number of perennials to be planted. For the same reason these models require the least labour in the third year when seasonal crops cannot be intercropped with perennials and the perennials have not yet started to yield. The gradual increase in labour from the third year onward in all but one of the models is largely due to harvest labour.

258

Table 2. Ranking of models for Net Present Values at different discount rates for the two time horizons.

Years I to 10 farmer's time horizon

0% discount 5% discount 15% discount 30% discount

SO 238 SO 183 SD 205 SD 159 S1 177 S1 131 AS1 163 ASI 116 $2 151 $2 112 AS2 146 AS2 100 $3 133 $3 99 AS3 96 AS4 59 AS4 88 AS3 58

SO 118 SO 75 SD 104 SD 66 $1 79 S1 46 $2 68 $2 40 AS1 63 $3 36 $3 60 AS1 33 AS2 50 AS2 25 AS4 29 AS4 13 AS3 19 AS3 - 2

Years 1 to 20 planner's time horizon

0% discount 5% discount 15% discount 30% discount

SO 478 SO 297 AS1 446 AS1 250 AS2 445 SD 245 $1 410 AS2 242 $3 406 S1 242 AS3 392 $3 218 SD 387 $2 204 AS4 384 AS3 199 $2 345 AS4 199

SO 148 SO 78 SD 127 SD 69 S1 108 S1 49 AS1 99 $2 43 $2 92 $3 39 AS2 87 AS1 37 $3 87 AS2 26 AS4 66 AS4 19 AS3 56 AS3 5

Values in thousands of rupees. The average exchange rate in 1990 was Rs 40.06 per USS Discount rates used by farmers and planners in bold boxes. Analog forest models are bolded to visually emphasise the change in ranking as discount rates increase.

Key Model SO Seasonals only SD Seasonals declining

S1 SALT1 $2 SALT2 $3 SALT3 AS1 Analog SALT1 AS2 Analog SALT2 AS3 Analog SALT3 AS4 Analog SALT4

Ratio of components 100% seasonal crops 100% seasonal crops assuming 10% decline in net returns over

each 10 year period due to fertility loss 10 seasonal crops:5 coffee/pepper 6 seasonal crops: 6 dairy/fodder: 3 coffee/pepper 6 seasonal crops: 6 woodlot: 3 coffee/pepper 6 seasonal crops:6 analog forest: 3 coffee/pepper 4 seasonal crops: 9 analog forest :2 coffee/pepper 100% analog forest 100% analog forest established on one third of the system each

year over a three year period. Seasonal crops are grown on non-forested alleys in interim

259

~ ~ ~ ~ "~ l~ ~

._~ ~ ~ ; ~ ~~ E

~ ~ ~.~

E < -,, . ~ =

~. , -~. ~,Z:~

0

:=

~ . r

-=}.= ~; = ._~

o .: ~ B

~, ..~_~ ~1 ~ .-~ E

' ~ E -~ ~ = . - $ ~ |

=='-2 -Ir

~ ~

E~

~. :+2 ._.

iH

260

Seasonal labour distribution

Figure 4 shows the annual Time Concentration Indices of the models and how they change over the first ten years after establishment, while Fig. 5 shows the TCIs of four of the component production systems. TCIs are not included for the woodlot component because, apart from the establishment years, the main labour input is harvest which occurs perhaps only in the sixth, tenth and twentieth year. Furthermore tree harvest can be carried out in any season.

Once seasonal cropping and the coffee/pepper intercrop are established, labour requirements are very unevenly spread. Furthermore, with time the labour requirements of a coffee/pepper intercrop become more concentrated as harvest requirements increase. The analog forest shows a similar develop- ment although far less pronounced. The TCIs in the first two years are affected by the labour required for establishing the system and for the

90.0

80 .0

70.0

~_) 60 .0 " 0 u

t - O

" - - 50 .0

0 r - 40 .0 0

0

E ~_. 30 .0

20 .0

10.0

0 ,0

1 2 3 4 5 6 7 8 9 10

Year

$I

$3 $2 ,'AS2 , SO

AS3

Fig. 4. Time Concentra t ion Indices for the seven models for the first ten years.

70.0

6 0 . 0 t 261

50.0

X 0 "0 t -

O 40.0

r

O O r "

30,0

._ b-

20,0

SEASONALCROPS

COFFEE/PEPPER

ANALOG FOREST

/ \ / - _ _ DAIRY / FODDER

o.o I I I I I I I I 1 2 3 4 5 6 7 8 g 1 0

Y e a r

Fig. 5. Time Concentration Indices for four of the production systems for the first ten years.

production of temporary seasonal crops in the analog forest and coffee/ pepper intercrop.

The TCIs of the S 1 model are high because of the combination of seasonal cropping and coffee/pepper which both require labour mainly during the major wet season. This combined labour peak escalates over the years as harvest requirements for the coffee and pepper become greater. The general shape of this curve is reflected in all the other models to the extent that coffee/pepper is represented in the system. The seasonal labour distribution in the AS3 model remains very even due to the variety of harvest periods of its component crops in the analog forest. The analog forest component in the AS1 and AS2 models helps fill some of the gaps in labour requirements between wet seasons. However, while the absolute requirement for labour for

262

the AS1 and AS2 models is lower than for the seasonals-only model (SO), the seasonal distribution of its labour is still of the same order.

Discussion

System properties of model components

The modelling process has indicated the financial potentials of the various models and has also provided information as to possible effects of the models on the local labour force. However this is still an inadequate basis for commenting on the appropriate model(s) for promotion in the Upper Mahaweli catchment, as other economic, environmental and social properties of the models have not yet been clarified. For example, it is necessary to know something of economic stability, biophysical sustainability, and the contribution to the domestic needs of the farm family. Furthermore, from the point of view planning for soil conservation, it is necessary to have some idea how readily the the model(s) would be adopted.

As these properties of the models are a function of the properties of their components, the following discussion will deal with both categories, ie the models (S1, $2, etc.) and the components (seasonal crops, analog forest, etc). Table 3 draws the results of the modelling together with these other proper- ties discussed below in terms of the system properties of the components.

Financial productivity Land management agencies charged with assisting the development of a productive self-sufficient farming community are interested not only in the potential levels of productivity of the systems they promote but also in how quickly those levels are reached after establishment. This will determine the nature of subsidies and other inducements required to cover the shortfall in income in the early years of establishing perennial crops. Figure 2 clearly shows the degree to which annual income must be augmented if farmers are to be coaxed into perennial cropping systems. For example the shortfall in income to be recovered if farmers were to take up the AS1 model could be in the order of Rs 84,000 over seven years for 0.5 ha of cropping area.

Labour properties When designing agroforesty systems it is necessary to anticipate the impact on the people in the region, particularly in terms of changes in the labour pool [Kronick, 1984]. Some of the production components require high levels of hired labour for short periods of time (e.g. seasonal crops, coffee/ pepper) while the requirements of other components are spread more evenly throughout the year and may be met by family labour only (e.g. dairy/fodder, analog forest). Some components require very high labour input for estab- lishment, while the labour requirements of other components grow as the

263

system matures. Consequently the models differ greatly in the degree of employment generated for the landless in the community, the stability of that employment, and the levels of subsidies required to cover labour costs in establishment.

The analysis of labour requirements presented here cannot be used to state categorically the desirability of one system over another. This depends on the special circumstances of the target community and the capacity of any funding agency. For example although the labour requirements of a fodder- dairy component may be favourable to the land-holding family it does not offer any employment to those in the community without land. Also the cycles of seasonal cropping could generate alternately labour shortages and surpluses at different times of the year. The analog forest is possibly the most flexible system with regard to employment. It can provide employment for harvest of export crops (coffee and cardamon) which require 35 to 40% of the labour of this system, but it also requires frequent smaller labour periods that can be met by the family.

Economic and enviromental stability Stability of productivity is determined firstly by fluctuations in yield due to drought, pest and diseases, and secondly by seasonal and interannual fluctua- tions in producer prices. Systems that maintain a permanent ground cover and shade will be buffered against short term water and wind stress. Poly- cultural systems will also possibly be more resilient against losses due to pest and disease or at least against loss of income due to loss of a single crop.

The nature of price fluctuations depends greatly on the commodity but, within the range of commodities produced by the models under study, two generalizations can be made. Producer prices for seasonal crops in Sri Lanka vary greatly across the season and, although there is a secular upward trend, they cannot always be well predicted from year to year [Gunawardena and Chandrasiri, 1980]. Prices for export crops such as spice and beverage commodities tend to be more stable across the seasons, but with few exceptions (e.g. cardamon) have been steadily declining over the past five years due to international competition. In contrast the prices of dairy produce, fuelwood and timber, which are sold locally, are steady and rising. An analog forest producing commodities for the domestic fruit, vegetable and forest product markets alongside export commodities represents the most comprehensive hedge against market instability.

Biophysical sustainability Biophysical sustainability refers to the depletive or regenerative effects of the farming system on the soil resource and the biodiversity of wild flora and fauna in the region. The analog forest models would have a very positive effect on both these resources. The estimated soil erosion under the tradi- tional Kandyan forest garden, upon which the analog forest is modelled, is 0.05 t/ha/y [Krishnarajah and Sumanaratne, 1988]. This can be compared to

264

erosion of similar slopes under seasonal crops of 70 t/ha/y (tobacco) to 18 t/ha/y (carrot), and 40 t/ha/y under tea without conservation works. Erosion would be expected to be relatively low from a permanent sward of fodder grass in the dairy system and from under permanent cover of perennial alley crops. The degree of erosion from under a eucalyptus woodlot would depend upon the amount of grass and shrub undercover that can establish itself. This will depend on available light (in turn determined by size and slope of woodlot) and the exclusion of fire.

The analog forest is the system that most enhances regional biodiversity [Senanayake, 1987]. A survey of traditional forest gardens over four different climatic and elevational regimes in Sri Lanka revealed that 37% of tree species were endemic [Everett, 1991]. A survey of birds observed in associa- tion with landuse in the Uva Basin of Sri Lanka indicated that whereas forest gardens provided a refuge for 53 species, the remnants of natural forest supported 45 species, market gardens supported 38 species and eucalypt plantations only 25 species [Nuberg et al., 1994].

Contribution to the domestic needs of the farm family As traditional farming systems become commercialized, land and labour resources are channelled into a narrow range of crops to take advantage of market opportunities. The degree to which this produce can contribute to the nutrition and amenity of the farm family is important for reasons of nutri- tional diversity and subsequent family health, and maintenance of positive aspects of village culture [Marten, 1990]. The degree to which the various model components contribute t o domestic self-sufficiency ranges from virtually nil in the coffee/pepper system to extremely high in the analog forest.

The positive cultural aspects of the traditional forest garden are univer- sally accepted in Sri Lanka. The forest garden, along with the temple, rice paddy and traditional irrigation structures, is an icon of Sinhala culture and has inspired much of the rhetoric and indeed physical planning over recent decades. The analog forest, by extrapolation from its relationship to the forest garden, is well-placed to maintain the supply of these less tangible, but nevertheless very real, needs of rural society.

Likelihood of adoption by farmer How readily a system will be adopted by a farmer will be determined not only by the potential profits and how soon they come, but also by the market infrastructure for the produce, institutional support by way of extension services and subsidies, and resonance with dominant cultural values.

The quick profits and ready market for seasonal crops need no institu- tional encouragement. The coffee/pepper intercrop is strongly supported by the Department of Export Agriculture which offers subsidies until the crop comes into production. Assistance for smallscale dairies through the Depart- ment of Animal Production and Health is under review. Woodlots have been

265

promoted by the Forestry Department through a variety of programs, and the experience has been that private woodlots are more suceesful than community woodlots.

Although the analog forest proposed here is untested there have been many agencies involved with promotion of 'home-garden enrichment' pro- grams [Skutsch, 1990]. Farmers readily participate in these programs, possibly because of the recognized social and cultural values of the forest garden. There is reason to expect that analog forest models wll be readily adopted, provided immediate financial needs are met and ownership of the analog forest is secure.

Likelihood of effective management of soil conservation hedgerows Assessment of this is based partly on observation and partly on conjecture. The successful maintenance of soil conservation hedgerows already estab- fished in the Upper Mahaweli region has so far been disappointing (S. De Curtins, pers. comm.). One way to overcome this could be for the imple- menting agency to train and employ specialist teams to plant the hedgerows, thus ensuring a higher estabfishment success. Subsequent hedgerow main- tenance is, however, the responsibility of the farmer, but has not yet become part of the farming culture.

A change such as this requires more than just one-off subsidies or grants. It requires promotion of a soil-conserving cropping system with appro- priately attractive returns and a long term commitment by the extension services implementing it. Seasonal cropping, as it exists with bare cultivation of a monocrop, is inappropriate. Research and extension efforts should encourage intercropping of seasonal crops and the use of hedgerow material for mulching. Perennial intercrops grown in alleys and mulched by hedgerow loppings would enhance the soil conservation function of the hedgerows. Similarly hedgerows lopped for fodder in the dairy system are likely to be well maintained. In both the woodlot and analog forest systems the hedge- rows are bound to atrophy as the trees grow. In the analog forest system the soil conservation function of the hedgrows is effectively replaced by the shrubs and ground cover, but this does not occur in the woodlot system.

Models appropriate to the Upper Mahaweli catchment

There is of course no single model that would suit the needs of all small- holders in all localities of the Upper Mahaweli catchment. Not all land- holders are farm families that five adjacent to their plots. Some landholders are non-resident businessmen concerned with only the quick returns of seasonal cropping. If hedgerow maintenance and mulching is resisted by these people then it may be better to provide assistance for bench and stonewall terracing. Other landholders may be more interested in tea or growing mulberries for sericulture and GTZ is busy promoting the use of contour hedgerows in these systems. The current philosophy of watershed

266

management is to present a 'basket' of possible models rather than a single inflexible 'package' [Sajise and Ganapin, 1990]. The models proposed here are for rainfed farms operated by a resident family and we are looking for the one that makes the best compromise beween financial productivity, steady employment, domestic nutrition, economic stability, and protection of the watershed.

Let us then briefly summarize the properties of the production systems that comprise the proposed models. The quick and potentially high returns from seasonal crops ensures their inclusion in any model but it is essential they be accompanied by a complementary component that provides some measure of economic and biophysical stability and sustainability. A woodlot won't provide this in the short term and is probably only appropriate on land of very poor quality. The livestock/fodder option described here also does not make economic sense. If a cow is to be kept, it would be best to continue the current practice of collecting wild fodder from along roadsides and watercourses, rather than dedicate 0.2 ha to the growing of fodder.

Dedicating every third alley to perennial crops, along the lines of the SALT models, offers a partial solution. Although the economic future of the coffee/pepper intercrop is uncertain it still receives substantial institutional support in Sri Lanka. There is obviously a need for research into an alterna- tive perennial alley crop. An intercrop of banana-papaw-lime, for example, is quite feasible for this area and has the potential of yielding far in excess of any existing systems within the first three years after establishment (details available from the principal author).

However, a farm model consisting only of seasonal crops and a perennial alley intercrop, such as the $1 model, would still be lacking in some of the important stability, biophysical sustainability and social properties. For this reason the AS1 model, with 40% seasonal crops, 20% perennial alley crops and 40% analog forest has much to offer. From a planner's perspective (using a 0 to 5% discount rate over twenty years in Table 2) it is also more financially productive than S1. From a farmer's perspective (using 30% discount rate) over the same time period, AS1 is only Rs 600/y less profit- able than $1 yet it offers incalculably more in environmental and social amenities for both the individual and the community. With 60% of the land under perennial cover, this model also provides excellent watershed protection.

Financial analysis should be used to help understand resource allocation problems facing farmers and planners, and identify areas of uncertainty and potential trade-offs but not to make decisions [Magrath, 1990]. The decision- making process based on the knowledge gained here has to balance eco- nomic concerns with those of conserving the biophysical resource base and the future of rural society and culture.

Seasonal cropping is financially productive but not sustainable. To make it more sustainable government or project funds could be directed to research and extension of soil-conserving agronomic techniques such as intercropping,

267

minimum tillage and mulching. However, from a broader perspective there is a stronger case for providing inducements to encourage the establishment of the mixed analog forest models.

The extension of the analog forest concept to other tropical uplands

The value of the analog forest concept studied here goes beyond its local potential for sustainable agriculture in the Sri Lankan uplands. This paper has shown how it has many properties desirable for sustainable development that would be generally applicable to tropical uplands. However in the context of the Upper Mahaweli an analog forest is not sufficient in itself as a farm model. Some general points can be made on the constraints on the development of the analog forest system from lessons learnt in this research.

The point of constructing composite farm models is that each of the model components examined here has unique properties, the value of which are best realized when complemented by systems with other properties. Thus an appropriate combination of systems in Sri Lanka is a model with: (a) seasonal crops for quick and high income earning capacity; Co) perennial crops such as coffee/pepper to earn export income for the nation; and (c) an analog forest for economic stability, domestic health and environmental protection. How- ever the socio-economic parameters that make this model appropriate for Sri Lanka are not universal.

These parameters are highly interrelated and include: population density, land hunger and the level of rural unemployment; the degree of commer- cialization of the local economy, distance from markets and sophistication of market infrastructure; the ability of local agencies to implement technology; and local familiarity with intensive forest-garden-type systems.

In some remote tropical uplands, where, for example, swidden agriculture is still practised, these parameters would be very different. The model appro- priate for Sri Lanka would not have a place in the highlands of Papua New Guinea. However analog forest systems may be appropriate for Javanese colonists of Kalimantan and other 'outer islands' of the Indonesian archi- pelago who bring with them a culture familiar with intensive forest garden systems (see Ross [1984]). The degree to which analog forest systems can also fulfill commercial needs and compete with seasonal cropping depends on local climate, soils and species and the commercial demand for analog forest products.

As the uplands of tropical Asia becomes increasingly settled and defor- ested and as the local economies become more commercialized, then so also will increase the need for mixed farming systems that provide commercial, domestic and environmental benefits. Analog forest systems have these values, but from experience in Sri Lanka it would seem they may often need to be incorporated with other forms of production. Furthermore their high establishment costs and low initial financial returns will make it necessary for governments wishing to ensure long-term economic, social and biophysical

268

sustainability to provide incentives for individual farmers to include such systems as part of their total farming operations.

Acknowledgements

The authors gratefully thank Bernhard Mohns and Silvio De Curtins of GTZ/UMWP, Kandy, for the opportunity and resources to carry out the necessary field work. In addition the contributions of A. Priyantha of The Nation Co-operative Council of Sri Lanka, R. Wagachchi of the Department of Export Agriculture, and R. Senanayake and Y. Everett of the NeoSyn- thesis Research Centre to the development of the species list for the analog forest are acknowledged. Thanks are also extended to two anonymous referees for their suggestions.

References

Altieri MA, ed (1987) Agroecology: The Scientific Basis of Alternative Agriculture. Westview Press, Boulder CO, 224 pp

Altieri MA, Letourneau DK and Davis JR (1983) Developing sustainable agroeco-systems. BioScience 33(1): 45--49

Bavappa KVA and Jacob VJ (1981) A model for mixed cropping. Ceres (May/June): 44--46 Bavappa KVA and Jacob VJ (1982) High intensity multi-species cropping. World" Crops

(March/April): 47--50 Bavappa KVA, Premaratne WHE and Ruettimann RA (1986) Minor export crop models for

mixed cropping and crop diversification. Department of Minor Export Crops, Government of Sri Lanka

Everett Y (1991) Homegardens in Sri Lanka: patterns and change in the highland landscape. Paper presented at Conference on Integrated Land-Use and Biodiversity in Tropical China. Jinghong, Xishuangbanna, China, October, 1991

Ewel JJ (1986) Designing agricultural ecosystems for the humid tropics. Annual Revue of Ecology & Systernatics 17:245--271

Gliessman SR, ed (1990) Agroecology: Researching the Ecological Basis for Sustainable Agriculture. Springer-Verlag, New York

Gunasena H and Hitinayake H (1990) Alley cropping with Gliricidia and Leucaena in the Intermediate Zone of Sri Lanka. In: Gunasena HPM, ed, Multipurpose Tree Species in Sri Lanka: Research and Development, pp 72--79. Kandy, University of Perideniya, 157 pp

Gunatilake H (1990)Institutional aspects of soil conservation on tobacco lands and factors influencing tobacco farmers soil conservation decisions in the Hanguranketha-Walapane area, Sri Lanka. Unpublished MSc thesis, Agricultural University of Norway

Gunawardena PJ and Chandrasiri A (1980) Factors Influencing Vegetable Prices: A Study of the Vegetable Economy in Sri Lanka. Agricultural Research and Training Institute (ARTI), Colombo

Hart R (1980) A natural ecosystem analog approach to the design of a successional crop system for tropical forest environments. Biotropica (Tropical Succession Supplement) 12(2): 73--95

Hart R (1982) Designing agroecosystem management plans for small farms in tropical en- vironments. In: Hill S and Ott P, eds, Basic Techniques in Ecological Farming, pp 217-- 223. Birkh~iuser Verlag, Basel, 365 pp

Holdridge L (1959) Ecological indicators of the need for a new approach to tropical land use. Economic Botany 13:271--280

269

Hosier RE (1989) The economics of smallholder agroforestry: two case studies. World Development 17(11): 1827--1839

Jacob V and Alles W (1987). Kandyan gardens of Sri Lanka. Agroforestry Systems 5: 123-- 137

Krishnarajah P and Sumanaratne HD (1988) Magnitude and extent of soil erosion under different landuse in the midcountry region Sri Lanka. Krnshi 11 (1): 18--21

Kronick J (1984) Temporal analysis of agroforestry systems for rural development. Agro- forestry Systems 2:165--176

Magrath WB (1990) Economic analysis of soil conservation technologies. In: Doolette J and Magrath W, eds, Watershed Development in Asia: Strategies and Technologies, pp 71--96. World Bank, Washington DC, 170 pp

Marten GG, ed (1986) Traditional Agriculture in Southeast Asia: A Human Ecology Perspec- tive. Westview Press, Boulder, 250 pp

Marten GG (1990) A nutritional calculus for home garden design: case-study from West Java. In: Landaner K and Brazil M, eds, Tropical Home Gardens, pp 147--168. The United Nations University, Tokyo, 257 pp

Mohns B and Rajapakse K (1990) Two years experiences with MPTS in the Upper Mahaweli Watershed Management Project. In: Gunasena HPM, ed, Multipurpose Tree Species in Sri Lanka: Research and Development, pp 1--7. University of Perideniya, Sri Lanka, Winrock International, Bangkok

Nanayakkara V (1991) Agroforestry systems in Sri Lanka. In: Mellink Wet al., eds, Agro- forestry in Asia and the Pacific. Bangkok, Regional Office for Asia and the Pacific (RAPA), Winrock International, 304 pp

Newman SM (1985) A survey of interculture practices and research in Sri Lanka. Agro- forestry Systems 3:25--36

Nuberg I (1992) Evaluation of production components for biological erosion control in the Intermediate Zone Mid-Country of Sri Lanka. Deutsche Gessellschaft fiir Technische Zusammenarbeit (GTZ)/ Upper Mahaweli Watershed Management Project (UMWP), Kandy, 93 pp

Nuberg I, Evans D and Senanayake R (1994) The future of forest gardens in the Uvau uplands of Sri Lanka. Environmental Management (in press)

Rambo A (1982) Human ecology research on tropical agroecosystems in Southeast Asia. Singapore Journal of Tropical Geography 3(1): 86--99

Ross MS (1984) Towards a farm model for sustainable, low-input agroforestry systems in the humid tropics with reference to Indonesia, The International Trees Crops Journal 3: 49-- 61

Sajise P and Ganapin DJ (1990) An overview of upland devlopment in the Philippines. In: Blair G and Lefroy R, eds, Technologies for Sustainable Agriculture on Marginal Uplands in Southeast Asia, pp 31--44. Australian Centre for International Agricultural Research (ACIAR), Canberra, 128 pp

Senanayake FR (1987) Analog forestry as a conservation tool. Tiger Paper: Regional Quarterly Bulletin on Wildlife & National Parks Management 14(2): 25--29

Skutsch MM (1990) Social Forestry in Integrated Rural Development Planning. FAO, Bangkok, 30 pp

Sri Lankan Department of Agriculture (series from 1980 to 1990) Cost of production of agri- cultural crops. Seasonal pubhcation of the Economics and Planning Division, Perideniya

Sri Lankan Department of Agriculture (1990) Crop recommendatous for adoption in Grama Niladari Divisions of Sri Lanka, Perideniya

Tacio HD (1991) The SALT System: agroforesty for sloping lands. Agroforestry Today 3(1): 12--13

Tacio HD (1992) Sustainable agricultural land technology. Unasylva 43(171): 50--55 TAMS (1980) Environmental Assessment: Accelerated Mahaweli Development Program, Vol

2, Terrestrial Environment. Tippets-Abbett-McCarthy-Stratton, New York Weerakoon W and Seneviratne A (1984) Managing a sustainable farming system in the dry

zone of Sri Lanka. The Tropical Agriculturalist 140:41--50