When is the best time to top-dress winter wheat?

Winter wheat should be top-dressed at the seedling stage, overwintering stage, greening stage, jointing stage, booting stage, and after heading. Apply farmyard manure at the seedling stage, ammonium bicarbonate or urea from the overwintering stage to the booting stage, and urea after heading. If the base fertilizer and seed fertilizer are relatively sufficient, there is no need to top-dress at the seedling stage; if seedling fertilizer has been applied, the overwintering fertilizer may be omitted; if the base fertilizer is sufficient and the tillers are strong and numerous, greening fertilizer should not be applied.

1. Seedling stage top-dressing: generally at the early tillering stage after emergence, apply 75-150 kg of ammonium bicarbonate or 45-75 kg of urea per hectare, or a small amount of human feces and urine. For wheat fields with relatively sufficient base fertilizer and seed fertilizer, top-dressing at the seedling stage may be omitted.

2. Overwintering stage top-dressing: in northern regions, apply fertilizer together with the freezing water irrigation; nitrogen fertilizer may be applied around Minor Snow, with 75-150 kg of ammonium bicarbonate or 45-75 kg of urea per hectare. For fields where seedling fertilizer has been applied, the overwintering fertilizer may be omitted.

3. Greening stage top-dressing: apply 225-300 kg of ammonium bicarbonate or 45-75 kg of urea per hectare, preferably by deep application of more than 6 cm. For wheat fields with sufficient base fertilizer and strong, numerous tillers before winter, greening fertilizer generally should not be applied.

4. Jointing stage top-dressing: mainly nitrogen fertilizer. Excessive-vigor seedlings should not be top-dressed with nitrogen fertilizer; strong seedlings should receive a small amount of nitrogen fertilizer, with 150-225 kg of ammonium bicarbonate or 45-75 kg of urea per hectare, together with phosphate and potassium fertilizers, applying 75-150 kg of superphosphate and 45-75 kg of potassium chloride per hectare; weak seedlings should receive more quick-acting nitrogen fertilizer, with 300-600 kg of ammonium bicarbonate or 150-225 kg of urea per hectare.

5. Booting stage top-dressing: mainly nitrogen fertilizer, in small amounts, generally 75-150 kg of ammonium sulfate or 45-75 kg of urea per hectare.

6. Top-dressing after heading: a certain amount of nitrogen, phosphorus, potassium and other elements is needed. For wheat fields with yellowing leaves and signs of fertilizer deficiency and premature senescence, spray 750 liters of 1%-2% concentration urea per hectare; for wheat fields with dark green leaves and a tendency toward excessive vegetative growth and late maturity, spray 750 liters of 0.2% concentration potassium dihydrogen phosphate solution per hectare.