Effect of drip irrigation and nitrogen management on inorganic nitrogen content and nitrous oxide emission in maize-planting soil

Objective  The objectives of this study were to obtain a rational drip fertigation mode for reducing nitrous oxide (N₂O) emission in maize-planting soil, and reveal the effects of soil inorganic nitrogen content on N₂O emission under different drip irrigation amount and nitrogen fertigation ratios.

Method  In the mobile rainproof shelter, two-season maize experiments with three drip irrigation amount (W₆₀, W₈₀ and W₁₀₀ were 50%−60%, 70%−80% and 90%−100% of field water holding capacity, respectively) and two nitrogen fertigation proportions (F₅₅: 50% nitrogen fertilizer applied to soil as basal fertilizer, and 50% nitrogen fertilizer as fertigation, F₃₇: 30% nitrogen fertilizer applied to soil as basal fertilizer, and 70% nitrogen fertilizer as fertigation; Both of F₅₅and F₃₇ had the equal nitrogen rate of 180 kg·hm⁻²) were carried out. The soil N₂O flux over the whole growth stage and soil inorganic nitrogen content at different growth stages were measured. Soil N₂O emissions at the different growth stages and over the whole growth stage were calculated and the relationships between soil N₂O flux and soil inorganic nitrogen content were analyzed.

Result  The N₂O emission fluxes of corn soil in two seasons were similar. Under the same nitrogen application ratio, soil N₂O emission fluxes under W₁₀₀ water treatment were higher than those under W₆₀ and W₈₀ in most maize growth periods, indicating that soil N₂O emission fluxes under high water treatment were higher than those under medium and low water treatment. Under the same water treatment, soil N₂O emission flux ratio of F₅₅ was lower than that of F₃₇ except in summer maize seedling stage. During the whole growth period, the cumulative emission of soil N₂O under W₆₀F₅₅ treatment in spring was lower than that under other treatments, followed by W₈₀F₅₅, while those under W₆₀F₃₇ and W₈₀F₅₅ treatments in summer were lower. In addition, in two seasons, soil N₂O flux was significantly correlated with nitrate nitrogen and nitrite nitrogen contents, with correlation coefficients ranging from 0.433 to 0.579 and 0.396 to 0.532, respectively.

Conclusion  W₈₀F₅₅ treatment (70%−80% field water holding capacity, 50% nitrogen fertilizer as basal fertilizer and 50% nitrogen fertilizer as fertigation) reduces N₂O emission from maize-planting soil. In addition, soil nitrate nitrogen and nitrite nitrogen contents significantly affect soil N₂O emission.