Removal of nitrogen, phosphorus and potassium by rice-wheat double cropping system as affected by duration of rice variety, methods of planting rice and levels and sources of nitrogen

Summary

Removal of NPK in the rice-wheat double cropping system was studied in a field experiment conducted for two crop years (1977–79) at the Indian Agricultural Research Institute, New Delhi. The double cropping system producing 8×10³ kg/ha/yr grain (4.5×10³ kg rice and 3.5×10³ kg wheat) removed 166 kg N, 35 kg P and 174 kg K per hectare per year. Thus the rice-wheat double cropping system heavily depletes the soils of their NPK content and calls for balanced fertilization for continued high production.

NPK removal was higher when a 135-day duration rice variety was grown than when a 105-day duration variety was grown, because the former resulted in overall (rice + wheat) more grains and straw. Similarly grain and straw yield and NPK removal was more with transplanted rice than when sprouted rice seeds were sown on puddled seedbed; the latter method was in turn superior to direct drilling. Use of urea briquette, neem cake coated urea and sulphur coated urea gave higher yields and resulted in removal of more NPK than prilled urea.