Reduced mineral fertilization coupled with straw return in field mesocosm vegetable cultivation helps to coordinate greenhouse gas emissions and vegetable production

Abstract

The partial substitution of mineral fertilizers with straw in agricultural soils could help to control soil acidification, reduce the risk of eutrophication from agricultural runoff, and increase the utilization efficiency of straw. However, the effects of such coupled practices on greenhouse gas (GHG) emissions and production yields in vegetable fields are not clear. Therefore, the objectives of this study were to (1) understand methane (CH4) and nitrous oxide (N2O) emissions in response to the same amounts of straw return with varied amounts of mineral fertilizers, and (2) to identify a solution which could better coordinate GHG emissions, vegetable production yield, and the utilization of agricultural straw following disposal. We conducted four-season (lettuce-cabbage-chili-lettuce) vegetable cultivation for 1 year using a control treatment (CT), mineral fertilization only (F), and four mineral fertilization treatments plus maize straw (FS, 0.7FS, 0.6FS, and 0.5FS). We then examined seasonal changes of CH4 and N2O fluxes, CH4 and N2O cumulative emissions, soil organic carbon (SOC), nitrate nitrogen (NO3−-N) and ammonium nitrogen (NH4+-N) content, vegetable yields, global warming potential (GWP), greenhouse gas intensity (GHGI), and N2O emission factors (EF). Compared to the F treatment, the application of maize straw increased the N2O flux significantly in the FS, 0.7FS, 0.6FS, and 0.5FS treatments. In treatments with added straw, the reduced application of mineral fertilizer led to a reduction in the cumulative N2O emission; this was due to the reduced content of NO3−-N content. The lowest CH4 flux and cumulative CH4 emission were observed in the 0.7FS treatment; this may be due to a form of competitive oxidation between CH4 and NH4+-N from urea. Furthermore, the application of maize straw in combination with a full dose of mineral fertilizers led to high GWP and GHGI values, which showed increases of 88.7% and 78.8%, respectively, in comparison with the F treatment. When taking SOC storage variations into account, which were caused by straw decomposition during cultivation, we identified a negative net GHGI (NGHGI) value (− 0.0448 kg CO2-eq kg−1 yield) in the 0.7FS treatment. This indicated that the NGHGI had decreased by 116.2% relative to the F treatment when based on similar vegetable yields. Straw combined with 70% mineral fertilizer led to better GHG emissions and vegetable yield when taking into account the carbon sequestration and decomposition caused by the addition of straw.