Fertilizer requirement of rice grown after potato-rice rotation*

Field studies were conducted from 1984 to 1987 to study the residual effect of NPK applied to potato on the manurial requirement of rice at the Central Potato Research Station. Patna. Recommended dose of 150 kg N, 60 kg P₂ 0₅ and 100 kg K₂ O/ha was applied to potato cv. Kufri Sindhuri and differential doses of NPK were gtven to rice cv. Sita. The results revealed that NPK applied to potato reduced the PK dose for rice by 50% in the first year and 100% in the second year of the rotation but there was no reduction in N dose. In the third year significantly higher grain yield was obtained with the recommended dose of 80 kg N, 40 kg P₂ 0, and 20 kg LK₂ O/ha, compared to all the other treatments. It is concluded that rice grown after potato may be supplied with 80 kg N, 20 kg P₂0₅ and 10 kg K₂O/ha in the flrst year, only 80 kg N/ha in the second year and 80 kg N, 40 kg P₂0₅ and 20 kg K₂O/ha in the third year of potato-rice rotation.