N2O emissions in a long-term soil fertility experiment under maize–wheat cropping system in Northern India

Abstract The agriculture sector is a major contributor towards global N 2 O (nitrous oxide) emissions. Amongst various factors controlling N 2 O emissions from cultivated fields, application of fertilizers and manures is the key factor. The effect of 42 years of continuous application of inorganic fertilizers and farmyard manure (FYM) on N 2 O emissions in loamy sand soil was studied via closed chambers and gas chromatography. Daily N 2 O fluxes from five treatments: 100% NPK (T 1 ), 150% NPK (T 2 ), 100% N (T 3 ), 100% NPK + FYM (T 4 ) and Control (T 5 ), of an onging experiment under maize-wheat cropping system on Typic Ustochrept in Northern India, were measured during maize and wheat crop seasons. The average N 2 O fluxes in T 1 , T 2 , T 3 , T 4 and T 5 treatments during maize crop season were 56.2, 60.8, 58.5, 59.2 and 24.6 N 2 O-N g ha − 1  day − 1 , respectively and in the wheat crop season 17.1, 19.7, 17.2, 19.4 and 11.5 N 2 O-N g ha − 1  day − 1 , respectively. Total N 2 O emissions in long-term fertilizer or manure treatments were approximately 100 and 50% higher than control in the maize and wheat crop seasons, respectively. Various long-term treatments had significant effect on status of various soils C and N forms, which in-turn influenced N 2 O emissions. Regression analysis revealed that water-input either from rainfall or irrigation controlled nearly 50% of the seasonal variations in N 2 O fluxes in the control treatment and about 20% variations in fertilizer and manure treatments. This suggested that in addition to irrigation or rainfall, fertilizer application also played an important role in N 2 O emissions. Although carbon-equivalent emissions were higher from balanced fertilization or FYM application treatments, yield-scaled global warming potentials (GWP) were lower due to higher maize and wheat grain yields in these treatments. Long-term maize-wheat cropping without any nutrient application or imbalanced fertilization resulted in higher yield-scaled GWP. The findings suggested that to achieve food security and curtail N 2 O emissions, balanced fertilization or integrated nutrient management may be adopted.