Basal application of controlled-release nitrogen fertilizer increases Chinese cabbage production and decreases soil NH₃ and N₂O emissions in Northern China

Objectives This study aimed at exploring the potential of one-time basal application of controlled-release nitrogen fertilizer (CRU) on reducing NH₃ and N₂O emission and increasing economic benefits of Chinese cabbage production in Northern China.

Methods A micro-plot field experiment was conducted in Zhaoxian County, Hebei Province. Fertilization treatments included no fertilizer control (CK), routine urea N at 400 kg/hm² and 10% less rate treatment, both applied in basal∶topdressing ratio of 4∶6 (U, 90U), and CRU in 10% less N input and totally basal applied (90CRU). Aeration methods and closed static chamber-gas chromatography methods were used to monitor and analyze soil NH₃ and N₂O emission during growing period. At harvest, the Chinese cabbage yield and N use efficiency were determined.

Results The NH₃ emission peaked in U and 90U treatments 3–6 days after basal fertilization and 3–5 days after topdressing, while that in 90CRU attained its peak at 9–11 days after basal fertilization, and with significantly lower peak value than U and 90U treatment. Compared with 90U treatment, the fluxes and accumulation of soil NH₃ emission in 90CRU were decreased by 46.9% and 27.6% (P<0.05) during the whole growth period. The N₂O emission peaked in U and 90U treatments at 7–9 days after basal fertilization and 4–6 days after topdressing, while that in 90CRU was 14–17 days after basal fertilization, and with significantly lower peak value than U and 90U treatment. Compared with U, 90U treatment decreased emission flux and total N₂O emission by 11.1% and 8.8%, 90CRU treatment significantly decreased total N₂O emission by 50.5% and 23.2% during the whole growth period, increased the yield of Chinese cabbage and net economic benefit by 7.8% and 8.0% respectively, and nitrogen use efficiency by 5.7 percentage points. The relationship between NH₃ emission flux and soil urease activity was a positive linear correlation, therefore, NH₃ flux was significantly reduced by reducing soil urease activity in 90CRU treatment. Further, there was a positive linear correlation between N₂O emission flux and NO₃^–-N content and the number of functional genes AOB-amoA and nirK. Therefore, N₂O emission flux was significantly reduced by the reduced indexes in 90CRU treatment.

Conclusions Controlled-released nitrogen fertilizer showed significance effect in reducing nitrogenous fertilizer and labor input, improved the yield and economic benefits, reduced NH₃ and N₂O emission, and provided an effective nitrogen management mode for Chinese cabbage planting in Northern China.