Choosing a pulse for a rice fallow with declining residual moisture
Bishnu Charan Das has 1.5 ha of medium land in Puri district. His paddy (cv. Pooja, 140 days) was harvested on 20 November, leaving residual soil moisture in a sandy loam of pH 6.3. He wants to use the fallow for a pulse crop but has no irrigation. He has 40 kg of greengram seed saved from last season, with a germination test of 78%, and can buy more. Sowing must be completed by 30 November because moisture is declining; the field is still wet in patches. He is considering chickpea (desi, 110 days) because it fetches a higher price, or lathyrus, which his neighbour grows. He has no rhizobium culture and plans to broadcast seed and cover it with a light harrow. The long-range forecast predicts a dry December and a possible early January cold spell. He wants a low-cost, low-risk recommendation.
1. Choose the crop and justify the choice using residual moisture, temperature, and market risk. Address chickpea and lathyrus explicitly.
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Choose greengram, not chickpea or lathyrus. Chickpea needs about 110 days and cooler temperatures; sown on 25 November in a rice fallow with declining residual moisture, it would face terminal moisture stress in December and likely fail, and it is more sensitive to waterlogging in the still-wet patches. Lathyrus is not a safe recommendation: it is restricted in many states because of the neurotoxin BOAA, and it has a long duration. Greengram fits the window: a short-duration variety (about 60–65 days) can be harvested by late January, before the cold spell intensifies and before moisture is fully exhausted. The market price is lower than chickpea, but a low-cost, low-risk crop with a moderate yield is better than a high-priced crop that fails. The saved seed has only 78% germination, so quality must be checked before sowing.
2. Calculate the seed rate for greengram for 1.5 ha after adjusting for germination, and describe seed treatment and sowing method.
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Recommended seed rate for greengram is about 20 kg/ha. For 1.5 ha, 30 kg of good seed is needed; at 78% germination, adjust to 30/0.78 = 38.5 kg, say 39 kg. He has 40 kg, which is just sufficient if the seed is free of admixture and not damaged; test a small sample for vigour. Treat seed with rhizobium culture and PSB, then with carbendazim or Trichoderma viride to control seed-borne disease; do not mix rhizobium with fungicide at the same time - apply the fungicide first, dry, then inoculate. Sow in lines 30 cm apart with 10 cm plant spacing, 3–4 cm deep, into moist soil, and cover lightly; avoid deep sowing. Use zero or minimum tillage to conserve moisture, and apply a light straw mulch if available. Basal fertilizer: a small starter dose of DAP at 50 kg/ha, since the soil is not very deficient in P but the crop needs early vigour.
3. Identify the main risk to this plan and give a contingency trigger.
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The main risk is failure of residual moisture before germination and establishment. Trigger: if there is no germination by 8–10 days after sowing, or if the top 10 cm is dry and seedlings are wilting, do not wait for a miracle. Options are to switch the field to a short-duration fodder crop or to prepare for a summer crop; do not spend more on fertilizer or sprays. If germination is uniform but the December dry spell is severe, one protective irrigation at flowering, if a farm pond is available, gives the best return. Keep the seed rate adjustment and treatment records so the next season's decision is based on evidence.