Comparing ammonia volatilization between conventional and slow-release nitrogen fertilizers in paddy fields in the Taihu Lake region

Pollution arising from ammonia volatilization in paddy fields could be reduced by using slow-release nitrogen fertilizers. In recent years, slow-release nitrogen fertilizers have been commonly used to replace conventional nitrogen fertilizers in the Taihu Lake region to reduce ammonia volatilization and improve nitrogen-use efficiency. To compare ammonia volatilization losses and examine the effects of different factors (N rates, types, field water NH4+, pH, and rainfall) between conventional nitrogen fertilizer and slow-release nitrogen fertilizer, paddy field experiments were conducted using conventional urea and sulfur-coated urea (SCU) fertilizers. The results indicated that ammonia volatilization flux positively increased with N application rate following an exponent function and depended on field water NH4+ concentration and pH. The ammonia volatilization under SCU treatment was 37.95-70.48 kg/hm(2), accounting for 40.66-52.86% of the fertilizer application rate. Compared with the same N input, the ammonia volatilization loss rate was 11.53-25.33% lower under the SCU treatment. Besides, SCU produced an unfavorable environment for ammonia volatilization, with a 1.15-2.61% decrease in pH and a 40.83-43.58% decrease in field water NH4+ concentration.