Impact of Integrated Nutrient Management on Soil Properties and Yield of Rice and Wheat in a Long-Term Experiment on a Reclaimed Sodic Soil

The effect of inorganic fertilizers alone and in combination with organic manures was evaluated for soil organic carbon (SOC), bulk density, available soil N, P, K and yields of rice and wheat grown on a reclaimed sodic soil after twelve years (1994–95 to 2005–06). The SOC increased in plots receiving N₁₂₀P₂₆K₄₂ plus green manure (GM) and N₁₂₀P₂₆K₄₂ plus farmyard manure (FYM) by 28 and 23% over the initial value but decreased by 31 and 24% in unfertilized and N₁₂₀P₂₆K₄₂ treated plots, respectively. Available N was highest in treatments receiving N₁₂₀P₂₆K₄₂ plus GM or FYM. Available P increased by 76% over its initial value of 11.8 kg ha⁻¹ in treatments receiving N₁₂₀P₂₆K₄₂ plus GM or FYM and by 28% where N₁₂₀P₂₆K₄₂ alone were applied. Application of NPK and its combination with GM and FYM increased rice yields significantly. Applying inorganic fertilizers in rice resulted in nearly similar nitrogen use efficiency (NUE) values when compared to their combined application with organic manures. The NUE increases in wheat due to the residual effect of organic manures in addition to the inorganic fertilizers. The rice yield declined by 3.3 and 8.9%, whereas the recommended dose of NPK (120-26-42 kg ha⁻¹) with organic manures (GM or FYM), the rate was decline by 7.7% and 14.3% for GM and 5.3% and 12.6% for FYM during five year's average (1999–2003) and two year's average (2004–2005), respectively in comparison to initial five year's average (1994–1998). However, due to the residual effect of GM and FYM on succeeding crop of wheat with N₁₂₀P₂₆K₄₂, the rate of yield decline was 5.2% and 6.0% for GM and 3.6% and 1.9% for FYM during the same years.