Late-Sown Wheat After a Delayed Rice Harvest
Ramesh farms 2.4 ha of sandy loam in Begusarai, Bihar. His rice crop was harvested only on 15 December because the monsoon withdrew late, and he broadcast wheat on 22 December using 100 kg/ha of HD-2967, a variety with about 145–150 days to maturity. Soil moisture was adequate at sowing and 80 kg N/ha, 60 kg P2O5/ha and 40 kg K2O/ha were applied basally. The field has no sprinkler, and canal water reaches the farm only for three irrigations. The India Meteorological Department forecast for March–April is for above-normal maximum temperatures, with several days above 36°C during grain filling. The farmer has 25 kg of urea left and can buy more only after 10 January. His neighbour advises him to keep the same variety because 'seed is already in the ground' and to apply all remaining urea at the first irrigation to push growth.
1. Should the farmer retain HD-2967 or change to a different variety? Justify your recommendation using the crop calendar, heat risk and the cost of re-sowing.
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HD-2967 sown on 22 December would mature around 15–20 May. Its grain-filling period would therefore fall in late April and early May, when the forecast is for several days above 36°C. Heat at grain filling causes forced maturity, shrivelled grain and low test weight; the variety's 145–150-day duration is the problem, not the seed lot. Re-sowing with a short-duration, heat-tolerant wheat such as HD-3086 (about 110–115 days) around 25 December would bring maturity to about 20–25 April, before the worst heat. The extra cost is roughly ₹3,000–4,000/ha for 125 kg seed plus sowing, while a conservative gain of 1 t/ha is worth about ₹24,000 at the wheat MSP. The judgement therefore favours re-sowing, provided the field can be prepared and sown within 3–4 days. If re-sowing is impossible, he should not spend more on nitrogen to 'push' the late crop; that would increase vegetative growth and worsen heat stress.
2. If he re-sows, what seed rate and nitrogen timing would you advise, and why should the seed rate differ from the normal 100 kg/ha?
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Late sowing shortens tillering and the vegetative period, so the normal 100 kg/ha is too low. With a short-duration variety sown in late December, use 125–150 kg/ha and sow in rows 20–22.5 cm apart at 4–5 cm depth. Nitrogen should be about 100–120 kg N/ha, not more, in two splits: half at sowing and half at the first irrigation (crown-root stage, about 20–25 days after sowing). Applying all remaining urea at the first irrigation, as the neighbour suggests, would release a large amount of nitrogen at once, produce soft succulent growth, increase lodging and make the crop more vulnerable to terminal heat. Phosphorus and potassium should go basal. If the field is already sown, the practical step is to apply the second urea split at CRI and avoid any late top-dressing after booting.
3. With only three irrigations assured, which crop stages should get water and how would you use the limited urea?
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With only three assured irrigations, prioritise the stages where water deficit causes irreversible yield loss: crown-root initiation (about 20–25 days after sowing), booting (about 55–60 days) and grain filling (about 75–80 days). In a late-sown short-duration crop these stages arrive earlier, so the first irrigation should not be delayed. Apply urea just before an irrigation, not on dry soil, to reduce volatilisation; place it in moist soil. If the crop is already dark green at booting, skip the urea at that stage and save it for the next crop. A light irrigation at grain filling is more useful than a heavy one, because waterlogging can cause lodging. Straw mulch or a bund around the field can help retain moisture between the three canal turns.