Abstract
Sustenance of soil fertility is a key challenge in intensive rice farming in subtropical agro-ecosystems due to unbalanced fertilization. Recommended fertilizer rates are assumed to optimize crop productivity but their effects on the maintenance of long-term soil fertility are not well studied. A long-term field experiment was evaluated for crop yield and soil properties after crop 54 and crop 60 of continuous practice with six treatments that varied the supply of N, P and K relative to current recommended rates (RFD - specified N, P, K, S, Zn and B fertilizer doses) and a zero-added fertilizer for an annual mustard-mungbean-rice rotation. Soil nutrient contents, organic carbon (SOC) and bulk density (BD) were determined at different soil depths. Long-term RFD maintained the annual N balance (0.7 kg ha− 1), produced positive P (17.2 kg ha− 1) and S (22.9 kg ha− 1) balances but negative K balance (-140 kg ha− 1) in soils with the highest system rice equivalent yield (13.3 t ha− 1) and marginal benefit cost ratio (9.6). The SOC, TN and extractable nutrients were higher in RFD than with higher doses except extractable P which was increased by higher P. While long-term RFD was the most profitable for crop production and achieved a neutral N balance between inputs and outputs, it caused soil K depletion and P and S accumulation. Our results give insights into the modifications to the RFD that better maintain not only yield and crop profitability but also long-term soil fertility.
