Effects of Nitrogen Application Rate on Ammonia Volatilization and Nitrogen Utilization in Rice Growing Season
YE Shi-chao1,3,＃; LIN Zhong-cheng1,2,＃; DAI Qi-gen1,*; JIA Yu-shu1,3;GU Hai-yan1; CHEN Jing-dou1; XU Lu-sheng1,2;WU Fu-guan2;ZHANG Hong-cheng1; HUO Zhong-yang1; XU Ke1;WEI Hai-yan1
1 Key Laboratory of Crop Genetics and Physiology of Jiangsu Province / Innovation Center of Rice Cultivation Technology in the Yangtze Valley, Ministry of Agriculture, Yangzhou 225009, China; 2 Agriculture Committee of Wujiang County, Wujiang 215200, China; 3 Agriculture Bureau of Guannan County, Guannan 222500, China; ＃These authors contributed equally to this paper; *Corresponding author, E-mail: email@example.com
In contrast experiments in sandy soil and clay soil, effects of nitrogen application rates on the concentration of NH4+N in surface water, the loss of ammonia volatilization from paddy field, the production of rice, the nitrogen utilization efficiency and the nitrogen content in soil profile were studied. The concentration of NH4+N in surface water and the amount of ammonia volatilization losses all increased as the nitrogen application rate increased, and peaked at 13 days after nitrogen application. The loss of ammonia volatilization from clay soil was lower than that from sandy soil. The amounts of ammonia volatilization losses after nitrogen application at different stages were as follows: N application for promoting tillering > The first N topdressing for promoting panicle initiation(applied at the last 4thleaf stage) > basal fertilizer > The second N topdressing for promoting panicle initiation(applied at the last 2ndleaf stage). The total loss of ammonia volatilization from clay soil was 10.49-87.06 kg/hm2, accounting for 10.92%-21.76% of the nitrogen applied; the total loss of ammonia volatilization from sandy soil was 11.32-102.43 kg/hm2, occupying 11.32%-25.61% of the nitrogen applied. The amount of ammonia volatilization and the concentration of NH4+N in surface water reached their peaks at the same time after nitrogen application; the maximum appeared at the tillering stage with their ratios from 23.76% to 33.65%. With the increase of nitrogen application rate, rice production and the nitrogen accumulation in plants increased, but nitrogen use efficiency decreased. Rice production and the nitrogen accumulation in plants in clay soil were slightly higher than those in sandy soil. Soil nitrogen content in the depth of 4050 cm was the lowest; soil nitrogen content in the same layers increased with the increasing nitrogen application rate, and soil nitrogen content in clay soil was higher than that in sandy soil. From the view on ammonia volatilization, it is found that the amount of ammonia volatilization would increase quickly when the nitrogen application rate exceeded 250 kg/hm2 in rice growing season. However, from the view on rice production, the suitable nitrogen application rate should be about 300 kg/hm2. Therefore, considering highyield and environment protection, the appropriate nitrogen application rate was from 250 to 300 kg/hm2 in the condition of the experiment.
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