Abstract:
A long-term experiment was conducted to investigate the effects soil labile nitrogen pools and soil enzyme activities have on ammonia volatilization in the root zone of winter wheat under different cultivation modes. A split-zone experimental design was used in this experiment, The main zones were conventional cultivation, straw return, and film mulching, while the secondary zones were no nitrogen application, conventional nitrogen application, and conventional nitrogen reduction by 20%. 0-20 cm of wheat root zone soil was collected 42, 166, 194, and 217 days after sowing of winter wheat in the fifth season and inter-root soil of wheat was collected 42 days after sowing to determine soil nitrate-ammonium nitrogen, microbial biomass nitrogen, soil nitrate reductase, hydroxylamine reductase, and urease activities. The ammonia volatilization from agricultural soils was also collected during the wheat season in order to analyze the response of ammonia volatilization to the cultivation pattern, soil labile N pools, and soil enzymes. The results found total season ammonia volatilization accumulation in wheat to be significantly lower (p<0.05) in the film mulching treatments (6.41-7.38 kg hm
-2) than in the straw return (8.37-9.45 kg hm
-2) and conventional tillage treatments (8.81-11.06 kg hm
-2) with identical fertilization levels. The microbial biomass N content was found to be significantly higher (p<0.05) in the straw return treatment compared to the conventional tillage and film mulching treatments. Soil ammonia volatilization was found to have a significant positive correlation with soil ammonium nitrogen, microbial biomass nitrogen, and urease activity under straw return treatment (p<0.05). It also had a significant positive correlation with soil ammonium nitrogen, microbial biomass nitrogen, hydroxylamine reductase, and urease activity under mulch treatment (p<0.01). This study describes the effects soil labile N pools and soil enzyme activities have on ammonia volatilization in the root zone of winter wheat under different cultivation modes and this can provide theoretical support for subsequently reducing ammonia volatilization losses and improving the utilization of N fertilizer.