Ammonia volatilization from a Chinese cabbage field under different nitrogen treatments in the Taihu Lake Basin, China

Ammonia (NH₃) volatilization is a major pathway of nitrogen (N) loss from soil-crop systems. As vegetable cultivation is one of the most important agricultural land uses worldwide, a deeper understanding of NH₃ volatilization is necessary in vegetable production systems. We therefore conducted a 3-year (2010–2012) field experiment to characterize NH₃ volatilization and evaluate the effect of different N fertilizer treatments on this process during the growth period of Chinese cabbage. Ammonia volatilization rate, rainfall, soil water content, pH, and soil NH₄⁺ were measured during the growth period. The results showed that NH₃ volatilization was significantly and positively correlated to topsoil pH and NH₄⁺ concentration. Climate factors and fertilization method also significantly affected NH₃ volatilization. Specifically, organic fertilizer (OF) increased NH₃ volatilization by 11.77%–18.46%, compared to conventional fertilizer (CF, urea), while organic–inorganic compound fertilizer (OIF) reduced NH₃ volatilization by 8.82%–12.67% compared to CF. Furthermore, slow-release fertilizers had significantly positive effects on controlling NH₃ volatilization, with a 60.73%–68.80% reduction for sulfur-coated urea (SCU), a 71.85%–78.97% reduction for biological Carbon Power® urea (BCU), and a 77.66%–83.12% reduction for bulk-blend controlled-release fertilizer (BBCRF) relative to CF. This study provides much needed baseline information, which will help in fertilizer choice and management practices to reduce NH₃ volatilization and encourage the development of new strategies for vegetable planting.