Effects of organic waste application on soil greenhouse gas emissions of a winter wheat field

Exploring the impact of returning organic materials to the soil on greenhouse gas emission characteristics of winter wheat fields can help to improve economic and environmental consequences. Based on 3 modes of organic material return (JF:straw return and cow dung; J:straw return; JZ:straw return and mushroom dregs) and 2 nitrogen levels (N1:243 kg·hm^-2; N2:216 kg·hm^-2), the fluxes of N₂O, CO_2, and CH₄ in winter wheat fields were monitored using the static chamber method and gas chromatography, and the effects of the different fertilization measures on cumulative greenhouse gas emissions and warming potential of wheat fields were studied. During the experimental period, the amount of fuel consumed by farm machines and the power consumed during irrigation and fertilizer application were recorded and transformed to their carbon equivalents using a transformation coefficient. In addition, crop yield and aboveground biomasses were measured and carbon sequestration calculated. The total GWP under each of the 6 treatments were estimated based on the identified parameters of the greenhouse effect. The results indicated that wheat fields served as sources of N₂O and CO₂ and sinks of CH₄. Nitrogen application and adequate irrigation increased CO₂ and N₂O in the soil, but weakened the characteristics of CH₄ as an atmospheric absorption sink. The total amounts of N₂O and CO₂ emitted were highest in the JF treatment, at 3.5 kg (N₂O-N)·hm^-2 and 19 689.67 kg (CO₂-C) hm^-2 respectively, and the absorption value of CH₄ in this treatment was 5.33 kg (CH₄-C) hm^-2, significantly higher than in both of the JZ and J treatments. The total amounts of N₂O and CO₂ in each treatment increased, and the total amount of CH₄ decreased, with an increase in the nitrogen application rate. The GWP of JFN2, JN2, and JZN2 treatments were all negative, which indicated that the farmland ecosystem is an atmospheric carbon sink when organic materials were returned to the field; nitrogen was reduced by 20%, and the carbon interception by wheat was 1 038-2 024 kg·hm^-2. The GWP values were positive and the JZN2 treatment-treated wheat yield was 8 061 kg·hm^-2, significantly higher than that of the JFN2 treatment. In summary, JZN2 treatment could ensure wheat yield and had the most favorable environmental effects, and thus was the best fertilization management model for winter wheat in this region