Yield and nitrogen use efficiency of rice-wheat cropping system in gypsum amended saline-sodic soil

It is critical to determine nitrogen use efficiency (NUE) to find to which extent higher rates of nitrogen can improve crop yield with effective management practices.Two-year field experiments were conducted to investigate yield and NUE of rice-wheat cropping system on saline-sodic soil.Treatments included were two nitrogen (N) application rates, i.e. 15% (N 115 ) and 30% (N 130 ) higher than the recommended rates for normal soil, along with gypsum at the rates of 50% (SGR 50 ) and 100% (SGR 100 ) of soil gypsum requirement.Results revealed relatively highest NO 3 -leaching for rice (161 and 145 mg L -1 ) and for wheat (97 and 93 mg L -1 ) during 2011-12 and 2012-13, respectively in N 130 + SGR 100 .In this treatment, crop yield and NUE were the highest as compared to the other combinations.This resulted in reduction of yield gap by two-fold (53% to 26%) between saline-sodic and normal soils for rice-wheat.Interestingly, N 130 + SGR 100 proved most effective during the first year, however, N 100 + SGR 100 became more profitable in the subsequent year.Pearson correlation coefficients predicted significant positive correlation (p < 0.01) of yield and NUE with soil organic matter, cation exchange capacity and infiltration rate while inverse relationship was observed with electrical conductivity, pH, CaCO 3 , and bulk density.Based on data, it is concluded that the recommended N application together with SGR 100 would be environmental-friendly and economically viable option for rice-wheat cropping system in saline-sodic soils.