Late Wheat Sowing After a Delayed Paddy Harvest
Harpreet farms 6 acres in Ludhiana district. His paddy was harvested on 5 November after a delayed canal rotation, and the field is still wet in patches. He plans wheat on 3 acres. He has 120 kg of PBW 725 seed left from last year, with a tested germination of 78%, and the local dealer has DBW 187 and HD 3086. His soil test shows medium available nitrogen, low phosphorus, medium potassium and pH 8.3. The tube well delivers about 5 cm per irrigation in 10 hours; canal water is unlikely before 20 December. Last year he sowed on 28 November with 40 kg/acre of seed and harvested 17 quintals/acre, while a neighbour who sowed on 8 November got 21 quintals/acre. Labour is available only until 20 November. He must also fix the fertilizer split and the date of the first irrigation.
1. Which variety and seed rate should he use for sowing on 18 November on 3 acres, and what should he do with the old PBW 725 seed?
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Sowing on 18 November is about two weeks late for PBW 725, a timely-sown variety; late sowing shortens tillering and grain filling. Choose a short-duration late-sown type such as DBW 187, or another notified late-sown variety available locally, rather than HD 3086, which is also a timely-sown type. Do not use the old PBW 725 seed: 78% germination is below the 85-90% minimum expected of certified seed, and stored seed may also have poor vigour and seed-borne infection. If it had to be used, the rate would be adjusted by the germination factor: 40 kg/acre x 90/78 is about 46 kg/acre, and for late sowing a further rise to roughly 50 kg/acre is normal, giving about 58 kg/acre or 175 kg for 3 acres, which he does not have. Buying about 150 kg of fresh DBW 187 at 50 kg/acre is the safer choice. Treat the seed with a recommended fungicide before sowing.
2. Work out his per-acre fertilizer materials and the timing of nitrogen, and state what you would change because sowing is late.
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Per acre the recommendation is 50 kg N, 25 kg P2O5 and 12.5 kg K2O. DAP 18-46-0 at 55 kg supplies 25 kg P2O5 and about 10 kg N, so urea needed is (50 - 10)/0.46, about 87 kg. MOP at 21 kg supplies 12.5 kg K2O. Apply all DAP and MOP at sowing, placed about 5 cm below and slightly to the side of the seed, not broadcast on this alkaline soil. Because sowing is late, do not follow a leisurely three-split nitrogen plan: apply half the urea (about 43 kg) at sowing and the rest at the first irrigation around 25-30 days after sowing. A third split at 45-50 days is of little use once tillering is over. If patches are still wet, wait for tillage moisture rather than sowing in slush; sowing into poor tilth is worse than a further two-day delay. Correct drill placement matters more than an extra bag of urea.
3. When should the first irrigation be given, and how should he plan the remaining irrigations given the canal uncertainty?
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The first irrigation is the most critical (crown root initiation), and in a late-sown crop it should come at about 25-30 days after sowing, around 13-18 December, not at 35-40 days. Canal water is not expected before 20 December, so plan the first irrigation from the tube well and do not wait for the canal. At about 5 cm per 10 hours, 3 acres need roughly 30 hours of tube-well running per irrigation, so split it into two blocks so the whole field is not irrigated too late. After the first irrigation, give the second at tillering (about 45-50 days), then at jointing, flowering and milk stage; with late sowing, 4-5 irrigations are realistic. Light, timely irrigation suits this field better than heavy flooding, especially with wet patches and pH 8.3. Clean the channel and irrigate in the morning so surface wet patches dry before night.