Integrated management of green manure, farmyard manure, and nitrogen fertilizer in a rice‐wheat rotation in northwestern India

Sesbania (Sesbania aculeata) is an important green manure crop for wetland rice, and it can fix large amounts of N2. Farmyard manure (FYM) is traditionally a valuable source of nutrients, but it can meet only a part of the N requirement of the rice crop. Limited information is available on the nitrogen fertilizer value of green manure and complimentary and synergistic effects of green manure, FYM, and nitrogen fertilizer. A field experiment was conducted during 1989–1993 to evaluate the effectiveness of sesbania green manure and FYM (77–105 kg N ha‐1) applied either alone or in combination with green manure for wetland rice. Sesbania accumulated 90 to 135 kg N ha‐1 in 52 days. During each year, the total N addition to green manure and FYM amended plots was adjusted to 150 kg N ha‐1 by applying additional N through urea. The grain yield of rice increased significantly up to 150 kg N ha‐1. Green manure‐N proved as efficient as urea‐N in increasing rice yield. The availability of N from FYM was much lower than from urea or green manure. The combined application of FYM and green manure could meet all the N requirements (150 kg fertilizer N ha‐1) of the high‐yielding rice and improved the yield potential observed with urea alone. Physiological efficiency (kg grain kg‐1N uptake) was higher with green manure plus FYM treatment than urea or green manure alone. Incorporation of FYM alone or in combination with green manure increased organic carbon and available P and K contents in soil and significantly improved the yield of the succeeding crop of wheat.