Simultaneous reduction of greenhouse gas and NH emissions by combined application of organic and inorganic fertilizers in maize-cabbage cropping systems.

Intensive nitrogen (N) fertilization enhances crop yield but also increases ammonia (NH) and greenhouse gas (GHG) emissions (CO, CH and NO), requiring sustainable fertilization regimes. The co-application of organic and inorganic fertilizers can decrease the use of inorganic fertilizer, reduce environmental pollution, and enhance soil fertility. A simultaneous investigation of the effects of combined application of organic and inorganic fertilizers on NH volatilization, GHG emissions, and soil fertility is, however, lacking. The aim of this study was to investigate the effect of the co-application of organic and inorganic fertilizers on NH and GHG emissions by the static chamber method, greenhouse gas intensity (GHGI), soil properties, and productivity over two cropping seasons of maize and cabbage cultivation at two different soil type in 2020 and 2021. All treatments except the control (no fertilizer) were applied with equivalent N rates, including NPK, compost, and NPK + compost. Total NH volatilization increased significantly (p ≤ 0.05) in all fertilizer treatments compared to the control. Interestingly, the combined application of organic and inorganic fertilizers was effective on significantly reducing NH volatilization which showed 28-37% reductions and decreasing NO emissions by 61-62% over the NPK treatment in successive cropping seasons, mainly due to enhanced N retention in soils, irrespective of soil type. CO emissions increased in the compost amended treatments compared to the control, showing that compost application was the main contributor affecting the total GWP in upland soils. However, CH emissions were negligible on total GWP in both soil types. The combined application of inorganic and organic fertilizers significantly improved the physicochemical properties of the soils compared with the control and NPK treatments, and the improvement in the soil properties is equivalent to that of the compost treatment. The productivity of maize and cabbage increased significantly with N fertilization. However, there was no significant difference between the NPK treatment and the NPK + compost. The GHGI, a sustainability parameter, was the lowest in the NPK + compost throughout the successive growing seasons, irrespective of soil type. Therefore, co-application of inorganic and organic fertilizers to upland soils could be a sustainable and promising strategy for improving soil properties and crop productivity while minimizing greenhouse gas emissions and N losses.