Effect of biogas slurry and neem oil-treated urea sources on rice (Oryza sativa)- wheat (Triticum aestivum) cropping system

A field experiment was conducted during the rainy season (kharif) and winter season (rabi) of 1999–2000 and 2000–2001 at New Delhi, to study the effect of biogass slurry (BGS) and neem oil-treated urea sources on rice (Oryza sativa L.)-wheat (Triticum aestivum L emend. Fiori. & Paol.) cropping system. Except plant height, all the growth and yield attributes of rice such as effective tillers/hill, panicle length, filled grains/panicle and 1, 000-grain weight differed significantly due to different sources of N and their combinations with biogas slurry (BGS). Pusa neem micro-emulsion urea 120 (PNME₁₂₀) alone or with BGS in 70:30 gave the significantly higher grain yield of rice compared to prilled urea 120 (PU₁₂₀), BGS₁₂₀ and Pusa neem golden urea 120 (PNGU₁₂₀). The PNME₁₂₀ also recorded significantly higher apparent N recovery (59.3%) and agronomic efficiency (28.7 kg grain/kg N) compared to rest of sources and their combinations. Also, significantly more total N, P, K uptake was associated with PNME₁₂₀. Direct application of 60 kg N/ha to wheat significantly increased (16.6%) its grain yield over no nitrogen. Inorganic fertilizers applied to rice did not show significant influence on succeeding wheat crop. Biogas slurry resulted in the higher grain yield (3.97 tonnes/ha) than the control (3.14 tonnes/ha), prilled urea @ 120 kg N/ha (3.18 tonnes/ha), Pusa neem golden urea (3.37 tonnes/ha) and PNME (3.54 tonnes/ha). However, Pusa neem micro-emulsion urea significantly differed with the control, but not with rest of the sources. The PNGU₁₂₀ + BGS₁₂₀ in 50: 50 ratio resulted in higher grain yield (3.78 tonnes/ha) than (prilled urea + biogas slurry)₁₂₀ in 70:30 ratio, however it remained statistically at par with other combinations.