INFLUENCE OF ORGANIC AMENDMENTS ON NOx, NH3 EMISSIONS AND NITROGEN BALANCE FROM CROPLAND OF EUTRIC REGOSOLS

Croplands contribute significantly to the global nitrogen oxide (NOx) emissions, ammonia (NH3) volatilization, as well as nutrient pollution in water bodies, which is directly related to global warming and affects water and air quality. This study investigates the nitrogen (N) balance of croplands used for wheat-maize rotation farming using field free-drain lysimeters and incubation experiments. Six fertilizer treatments including regular mineral fertilizers (NPK), pig slurry as organic manure (OM), crop residues (CR), organic manure combined with mineral fertilizers (OMNPK), crop residues combined with mineral fertilizers (CRNPK) and a control plot without fertilizer (CK), were used for the field monitoring. N was applied at 280 kg N ha-1, 130 kg N ha-1 during the wheat season and maize season was 150 kg N ha-1. The results showed 0.44 to 10.04 kg N ha-1 average N2O flux from the croplands. The total N (TN) loss annually was found to be 8.3 to 27.6 kg N ha-1 but organic amendments in croplands significantly reduced TN losses through overland flow by 85% and 117% via interflow compared with NPK treatments. The organic N mineralization rate differed significantly among the organic amendments. Significantly higher N mineralization rates were found for OM (47.51 mg kg-1) and CRNPK (46.93 mg kg-1) as compared to other treatments (p < 0.05). The cumulative annual NOx fluxes ranged from 0.12 to 1.27 kg N ha-1 across the croplands. Compared to NPK, OMNPK and CRNPK treatments were found to decrease annual NOx fluxes by 45% and 186%, respectively. Similarly, OM, OMNPK, and CRNPK treatments increased the annual NH3 fluxes by 40%, 26%, and 24%, respectively. The annual NH3 fluxes varied from 15.90 to 31.03 kg N ha-1 while the annual N balance ranged from 103.1 to 164.2 kg N ha-1 across all treatments. A significantly higher N balance was found under CRNPK compared to other treatments, suggesting higher N retention in soils under CRNPK compared with NPK treatment (p < 0.05). This optimal N supply and higher N balance under CRNPK organic amendments made it recommendable to maintain crop yield in cropland of Eutric Regosols.