Agronomy of direct seeded Rice (Wet & Dry)

By E .Gracelin (BSA 07-424)

C. Habi Jeshinder (BSA 07- 425) Haldhar Kumar Singh (BSA 07-426)

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Direct Seeded Rice

Dry seeded rice

Wet seeded rice

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Introduction

Transplanted rice has deleterious effects on the soil environment for the succeeding wheat and other upland crops.

DSR which removes puddling and drudgery of transplanting the young rice seedlings provides an option to resolve the adaphic conflict and enhance the sustainability of rice-wheat cropping system.

Puddling requires lots of scarce water at a time when there is little water in the reservoirs, destroys soil structure and adversely affects soil productivity.

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Contd… DSR overcomes the problem of seasonality in labour

requirement for rice nursery raising and transplanting operations.

Non-development of ground water in kharif, late onset of monsoon and drudgery of operations often delays rice transplanting which leads to late vacation of fields. forcing farmers after the optimum sowing time.

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Contd…

DSR facilitates timely establishment of rice and succeeding winter crops.

Unlike puddle fields, DSR fields do not crack and thus help save irrigation water.

Surface retained residue serve as physical barrier to emergence of weeds, moderate the soil temperature in summers and winters, conserve soil moisture, add organic matter and nutrients to the soil on decomposition.

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Causes of Shift to Direct-Seeding

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Labor shortageSoil health issuesWater Shortage Economics

Direct seeding requirements

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Contd…

Need more uniform land levelling and better water management

Seed planted too deep results in poor emergence and weak plants

Seed planted too shallow is susceptible to bird and rat attack

Soil strength - For wet direct seeding, if a stick is dragged through the mud and the soil holds a shape, then the seed will not sink too deep.

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Contd…

If the shape freely collapses, then the seed will likely sink too deep and have problems emerging.

Lodging can be reduced by Transplanting (especially in the wet season), Choice of variety, Limiting N applications between Panicle Initiation and

flowering, and Reducing stem based diseases.

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Dry direct seeded Rice

Use Clean Seed -contributes to yield increase by 5-20% Weed pressure tends to be more in dry direct seeded

systems. Dry direct seeding can use more water and fertilizer if

there is no natural hardpan to limit infiltration and percolation

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Land preparation

Plough the fields during summer to control emerging weeds

Leveling the fields well facilitates uniform irrigation and better germination

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Machinery Requirement

Minimum-till drill/Power tiller drill Zero-till drill Bed drilling

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Seeding depth

Target planting depth - <1 cm, if drilled - 0.5 cm (maximum 1cm - Variety dependent)

Surface seeding can have problems of birds and rats - broadcast and harrow if possible

Seed rate - 80 to 120 kg seed/ha

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Methods of sowing

Broadcast/ Broad cast in furrow Drill seed in rows

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Broadcast/ Broad cast in furrow

Seed rate - 80 to 120 kg seed/ha Anaerobically sow in row :Seed rate - 60 - 80 kg/ha Seed should not be planted deeper than 1cm depth

Replanting bare patches One day after planting soak and incubate additional seed

(e.g., 1 kg). Around three days after planting, broadcast additional seed

in problem areas. 15 to 20 days after planting transplant seedlings to bare

patches, if required.

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Drill seed in rows

Seed rate - 80-90 kg/ha Seed should not be planted deeper than 1 cm depth replanting

bare patches Bare patches - depends on soil moisture One day after the field has sufficient moisture for germination,

soak and incubate additional seed (e.g., 1 kg/ha) Three days after planting, broadcast additional seeds in problem

areas. 15 to 20 days after planting transplant seedlings to bare patches

Wet direct seeded Use Clean Seed - Increase yields by 5-20%

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Seeding & Seeding time

Wait 1-2 days after land preparation (depending on soil texture ) to avoid seed sinking too deep - deep seed will have problems emerging if covered by mud and water

Drill the dry seed of normal rice at the start of monsoon i.e. when farmers put seed into nursery bed

May 3rd week to June 2nd week.

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Weed management

Pre-germinated weeds can be knocked down with glyphosate/grammoxone (at 0.5% two days before seeding) or by 1-2 very shallow ploughings (stale seed bed method)

Second flush of weeds can be removed manually

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Major issues:

Seed germination and emergence - Seed burried under mud water has difficulty in emerging.

Weed control Land levelling and early water management. Pests during crop establishment. Pre - germinate seed 48 hours before planting soak seed -

change water for every four hours if possible After 24 hours, incubate seed in the shade - rinse if

possible to avoid seed becoming too hot Seeding depth

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Contd…

Target planting depth - <1cm if drilled - 0.5 cm (maximum 1 cm - Variety dependent)

Surface seeding has fewer emergence problems than buried seed, but may have problems of birds and rats.

Soil tilth Rule of thumb - the soil is ready for planting if a "V" made by dragging a stick through the prepared soil holds its shape.

If the soil is too wet, the "V" will collapse indicating the seed will likely sink too deep and have problems of emergence.

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Wet Direct Seeded Rice

What is Wet Direct Seeding? In wet direct seeding, seed is normally pre germinated

prior to broadcasting onto recently drained, well-puddled seedbeds or into pre standingwater in the fields. Wet direct seeding more commonly used in irrigated areas.

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Why Use Wet Direct Seeding?

• Easier (less drudgery) and more timely crop establishment

• Reduced labor costs for crop establishment • Possible savings in water use

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How do you wet direct seed?

1. Ensure the field is well leveled, well puddle and weed free

2. Plant the field within 2-5 days after the final puddling. At this point the soil has settled to be solid enough to hold seed on or near the surface and weeds have not yet established. If seed is planted more than 1 cm deep, it will usually have problems emerging. 

3. In drained fields, small canalettes can be made across the field a couple of days after puddling to further help drain the field and avoid snail damage and seed emergence problems in areas with standing water.

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Contd..4. Pre-germinate the seed (soak for 24 hours in water, cover and

drain for 24 hours). In this time the seedling root will emerge 2-3 mm. If the seed is left longer it can become entangled making it difficult to separate seed and thus causing damage to the seed when planted.

5. Use sufficient seed - of a variety suited for direct seeding - to achieve a plant population of 100-150 plants/m2. This will usually require around 80 kg seed/ha. Use an extra 10-20% if the seed is not pregerminated. Farmers often use more seed

(e.g., up to 150-200 kg/ha) because of poor field leveling, poor seed and seed losses to birds and rats).

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Contd..

6. If water in the fields is muddy following the last working, allow the field to dry for a time period of at least 24 hrs (preferably 48 hrs) before broadcasting commences.

7. Sow the seed uniformly: Mark the field in 5 m wide strips (the typical distance over which seed can be uniformly distributed by hand). Divide the seed into uniform lots to allow the person sowing to sow up the field and back (i.e., a 10 m wide strip) before getting the next seed lot. (e.g., the field is 20 m wide, then there will be 4 passes of 5 m each and the seed should be divided into 2 equal size seed lots).

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Contd..

8. Broadcast the seed into 2-5 cm of standing water or onto the drained field. If the field is drained the soil should hold a “v” shape when a stick is run through the mud. This indicates a soil consistency that will prevent seed sinking too deep.

9. Let the water drain before flash flooding after 2-3 days to keep seed moist and to reduce soil crusting (this is especially important in the dry season)

 

10. If water is drained from the fields after broadcasting, it is reintroduced 10 to 15 days after establishment. In some irrigation areas, seedlings are broadcast post-germination with seedlings 100 to 300 mm in length.

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Limitations:

Good land preparation, leveling and water management are needed for uniform crop establishment.

Weeds are very serious in dry seeding and serious in wet seeding.

Snails (in wet seeded fields), and rats and birds can severely reduce plant stands.

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Contd..

Heavy rainfall at the time of crop establishment can result in crop establishment failure (especially in heavier clay soils), and if water sits over seed still germinating below the soil. 

Longer occupation of main field by 5-15 days, compared to transplanted rice.

High water and nutrient use in dry seeding (due to high percolation especially on light soils).

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Benefits of Direct Seeded Rice

Avoids repeated puddling, preventing soil degradation and plow-pan formation

Facilitates timely establishment of rice and succeeding crops as crop matures 10-15 days earlier

Saves water by 35-40%, reduces production cost by Rs 3000/ha, and increases yields by 10%

Saves energy: labor, fuel, and seed Solves labor scarcity problem and reduces drudgery of

labors

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The following table summarizes the principal considerations in moving from transplanting to direct seeding.

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Wet direct seeded Dry direct seeded  

No more nursery required No more nursery required

No more seedling pulling No more seedling pulling

Need to pre-germinate & incubate seed       -

Need improved water management       -

Need improved levelling       -

Surface seed can be attacked by birds and rats

Surface seed can be attacked by birds and rats

Weed more problematic Weed much more problematic

Seed planted too deep (>1cm) will have problems emerging       -

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