Effects of water-nitrogen interactions on NH3 and N2O emissions and yield in winter wheat cropland
To investigate the effects of different irrigation and nitrogen application modes on nitrogen gaseous loss in winter wheat farmland,we conducted a field experiment at Changqing Irrigation Experiment Station in Shandong Province,with two irrigation levels(80％-90％θf(I1)and 70％-80％θf(I2))and three nitrogen application levels(conventional nitrogen application of 240 kg·hm-2(N1),nitrogen reduction of 12.5％(N2),and nitrogen reduction of 25％(N3)).The results showed that ammonia volatilization and nitrous oxide emission rate peak appeared within 2-4 days after fertilization or irrigation.The ammonia volatilization rate during the chasing fertilizer period was significantly higher than that during the basal fertilizer period.Compared with other treatments,the ave-rage ammonia volatilization rate of I2 N2 treatment during the chasing fertilizer period was reduced by 10.1％-51.6％,and the average nitrous oxide emission rate over the whole growth period was reduced by 15.4％-52.2％.The ammonia volatilization rate was significantly positively associated with surface soil pH value and ammonium nitrogen content,while the nitrous oxide emission rate was significantly positively associated with nitrate content in topsoil.The accumulation amount of soil ammonia volatilization and nitrous oxide emission ranged from 0.83-1.42 and 0.11-0.33 kg·hm-2,respectively.Moderate reduction of irrigation water and nitrogen input could effectively reduce cumulative amounts of ammonia volatilization and nitrous oxide emission from winter wheat farmland.The cumulative amounts of ammonia volatilization and nitrous oxide emission under I1N3 and I2N2 treatments were signi-ficantly lower than those under other treatments.The highest winter wheat yield(5615.6 kg·hm-2)appeared in I2N2 treatment.The irrigation water utilization efficiency of I2 was significantly higher than that of I,,with the maxi-mum increase rate of 45.2％.Compared with N,and N3 treatments,the maximum increase rate of nitrogen fertilizer productivity and agricultural utilization efficiency in N2 reached 15.2％and 31.8％,respectively.In conclusion,the treatment with 70％-80％θf irrigation level and 210 kg·hm-2 nitrogen input could effectively improve the utiliza-tion efficiency of irrigation water and nitrogen fertilization and reduce gaseous loss from winter wheat farmland.
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