Abstract
Conservation Agriculture (CA) practices are being adopted in rice‐based intensive cropping systems in the Eastern Gangetic Plain (EGP) to improve soil fertility and system productivity, but very limited study was done regarding its effect on phosphorus (P) availability and balance. This study examined the effect of tillage practice, residue retention, and P fertiliser doses on P balance, P use efficiency (PUE), and system productivity in a rice‐based intensive cropping system. The experiment was initiated in 2015 with two factors, namely: tillage (strip planting = SP and conventional tillage = CT) and two levels of crop residue retention (high residue, HR = 50% rice + 100% lentil/40 cm mustard + 100% mungbean residues; and low residue, LR = 15% rice + no lentil/15 cm mustard + no mungbean residues). From 2018, it was converted to three factors with the splitting of plots for doses of P (lower dose = LD, 50% P of recommended dose (RD); 100% P of RD; and higher dose = HD, 150% P of RD). The yields of mustard and mungbean and the system yield were 13%–14%, 8%–13%, and 4%–5% higher in SP than CT, respectively, while rice yield was 6%–8% lower. Likewise, the yield of individual crops and the system yield were about 7%–10% higher in HR compared to LR. There was no response to increasing P fertiliser above the RD, but the LD depressed the yield of mustard, mungbean, and rice. The P balance (surplus) was positive (19 kg ha −1 year −1 ) under the current LR practice, while the HR retention reduced the positive P balance by 7% due to higher P removal by crops. The LD of P left a negative P balance, while the HD increased the positive P balance and decreased PUE. Therefore, we conclude that while HR coupled with SP increased crop yield, the current RD of P application remained optimal because of increased recycling of P in crop residues and P use efficiency.
