Response of soil characteristics and N2O emissions to fertilizer reduction strategies in highland summer vegetable production

Abstract

In recent years, the escalating application of nitrogen fertilizers in global vegetable production has positioned vegetable fields as significant sources of nitrous oxide (N₂O) emissions, eliciting widespread environmental concern. However, the interrelationships among fertilizer reduction gradients, soil physicochemical properties, microbial biomass nitrogen (MBN), enzyme activities, N₂O emissions, and yield in highland summer cauliflower (Brassica oleracea var. botrytis L.) systems remain inadequately elucidated. This study, conducted in Yuzhong County, Lanzhou City, Gansu Province, employed the “Green Stalk 100-day” cauliflower variety under three fertilization regimes: CK (conventional fertilization), F1 (20% fertilizer reduction), and F2 (40% fertilizer reduction). The impacts of these treatments on soil properties, MBN, enzyme activities, N₂O emissions, and yield were systematically evaluated. Results demonstrated that compared with conventional fertilization, both F1 and F2 significantly reduced soil organic carbon, nitrate nitrogen (NO₃⁻), ammonium nitrogen (NH₄⁺), total phosphorus, and MBN. Cumulative N₂O fluxes under F1 and F2 decreased by 30.01% and 63.35%, respectively, relative to CK, with a pronounced declining trend as the growing season progressed. Both greenhouse gas balance (GHG) and greenhouse gas intensity (GHGI) were markedly reduced under reduced fertilization regimes. Additionally, under the F2 treatment, the biomass and yield of cauliflower exhibited significant reductions of 17.41% and 25%, respectively, relative to the control (CK). In contrast, F1 achieved substantial mitigation of N₂O flux, GHG, and GHGI without compromising yield stability. In conclusion, the F1 treatment represents the optimal strategy for balancing economic and environmental benefits in highland summer cauliflower production systems in the Yuzhong region of Gansu Province.