Results showed that ammonia loss from urea broadcast into floodwater and incorporated into soil at transplanting was as high as 40% of applied N,and the corresponding total nitrogen (N) loss was 56%.Ammonia loss was m...Results showed that ammonia loss from urea broadcast into floodwater and incorporated into soil at transplanting was as high as 40% of applied N,and the corresponding total nitrogen (N) loss was 56%.Ammonia loss was measured with simplified micrometeorological method (ammonia sampler),and total N loss was concurrently measured using ^15N balance technique.The experiment was conducted under strong sunshine conditions on acid paddy soil derived from Quaternary red clay.The ammonia loss in this particular condition was much greater than those obtained from previous studies when urea was also applied to acid paddy soil but under cloudy conditions.It is concluded that the strong sunshine conditions with high temperature and shallow floodwater during the period of present experiment favoured ammonia volatilization.Application of stearyl alcohol on the surface of the floodwater reduced ammonia loss to 23% of applied N.However,the effect of stearyl alcohol was short-lived,probably due to the microbiological decomposition.展开更多
Ammonia volatilization losses, nitrogen utilization efficiency, and rice yields in response to urea application to a rice field were investigated in Wangzhuang Town, Changshu City, Jiangsu Province, China. The N ferti...Ammonia volatilization losses, nitrogen utilization efficiency, and rice yields in response to urea application to a rice field were investigated in Wangzhuang Town, Changshu City, Jiangsu Province, China. The N fertilizer treatments, applied in triplicate, were 0 （control）, 100, 200, 300, or 350 kg N ha^-1. After urea was applied to the surface water, a continuous airflow enclosure method was used to measure ammonia volatilization in the paddy field. Total N losses through ammonia volatilization generally increased with the N application rate, and the two higher N application rates （300 and 350 kg N ha^-1） showed a higher ratio of N lost through ammonia volatilization to applied N. Total ammonia loss by ammonia volatilization during the entire rice growth stage ranged from 9.0% to 16.7% of the applied N. Increasing the application rate generally decreased the ratio of N in the seed to N in the plant. For all N treatments, the nitrogen fertilizer utilization efficiency ranged from 30.9% to 45.9%. Surplus N with the highest N rate resulted in lodging of rice plants, a decreased rate of nitrogen fertilizer utilization, and reduced rice yields. Calculated from this experiment, the most economical N fertilizer application rate was 227 kg ha^-1 for the type of paddy soil in the Taihu Lake region. However, recommending an appropriate N fertilizer application rate such that the plant growth is enhanced and ammonia loss is reduced could improve the N utilization efficiency of rice.展开更多
Total nitrogen (N) loss and ammonia volatilization from urea applied to flooded rice grown on a paddy soil in Zhejiang Province were measured by 15N balance and micro-meteorological methods, respectively. Floodwater p...Total nitrogen (N) loss and ammonia volatilization from urea applied to flooded rice grown on a paddy soil in Zhejiang Province were measured by 15N balance and micro-meteorological methods, respectively. Floodwater properties and ammonia loss from the circular plot were compared with those from the microplots. And the effectiveness of urease inhibitor, NBPT [N-(n-butyl) thiophosphonc triamide], was also tested Results showed that the total losses from urea broadcast and incorporated at transplanting (basal dressing) were similar with those from urea broadcast 12 days after transplanting (top-dressing) (51.5% and 48%, respectively, of applied N), and ammonia losses were low, the corresponding figures were 10.8% and 7.0% of applied N, respectively. Thus, denitrification was a much more important pathway of nitrogen loss than ammonia volatilization under the particular conditions. Addition of NBPT retarded urea hydrolysis, reduced pHs and ammoniacal nitrogen concentrations of floodwater for either the application of urea as basal or as top-dressing, but these effects were not translated into the reduction of total nitrogen loss. Floodwater pHs and ammonia loss in the microplots were apparently lower than those in the circular plot from urea applied as basal dressing; however, such differences were not found when urea was top-dressed. The frequently raining days occurred after top-dressing may be responsible for the insignificant effect of plot size on floodwater pHs and ammonia volatilization. It seems that the effects of plot size on floodwater properties and ammonia loss mainly depend on weather conditions, in addition to the height and leaf area index of the crop.展开更多
文摘Results showed that ammonia loss from urea broadcast into floodwater and incorporated into soil at transplanting was as high as 40% of applied N,and the corresponding total nitrogen (N) loss was 56%.Ammonia loss was measured with simplified micrometeorological method (ammonia sampler),and total N loss was concurrently measured using ^15N balance technique.The experiment was conducted under strong sunshine conditions on acid paddy soil derived from Quaternary red clay.The ammonia loss in this particular condition was much greater than those obtained from previous studies when urea was also applied to acid paddy soil but under cloudy conditions.It is concluded that the strong sunshine conditions with high temperature and shallow floodwater during the period of present experiment favoured ammonia volatilization.Application of stearyl alcohol on the surface of the floodwater reduced ammonia loss to 23% of applied N.However,the effect of stearyl alcohol was short-lived,probably due to the microbiological decomposition.
基金Project supported by the Knowledge Innovation Program of Chinese Academy of Sciences (No.KZCX2-413-3)National Natural Science Foundation of China (No.30390080)National Basic Research Program of China (No.2005CB121108)
文摘Ammonia volatilization losses, nitrogen utilization efficiency, and rice yields in response to urea application to a rice field were investigated in Wangzhuang Town, Changshu City, Jiangsu Province, China. The N fertilizer treatments, applied in triplicate, were 0 （control）, 100, 200, 300, or 350 kg N ha^-1. After urea was applied to the surface water, a continuous airflow enclosure method was used to measure ammonia volatilization in the paddy field. Total N losses through ammonia volatilization generally increased with the N application rate, and the two higher N application rates （300 and 350 kg N ha^-1） showed a higher ratio of N lost through ammonia volatilization to applied N. Total ammonia loss by ammonia volatilization during the entire rice growth stage ranged from 9.0% to 16.7% of the applied N. Increasing the application rate generally decreased the ratio of N in the seed to N in the plant. For all N treatments, the nitrogen fertilizer utilization efficiency ranged from 30.9% to 45.9%. Surplus N with the highest N rate resulted in lodging of rice plants, a decreased rate of nitrogen fertilizer utilization, and reduced rice yields. Calculated from this experiment, the most economical N fertilizer application rate was 227 kg ha^-1 for the type of paddy soil in the Taihu Lake region. However, recommending an appropriate N fertilizer application rate such that the plant growth is enhanced and ammonia loss is reduced could improve the N utilization efficiency of rice.
文摘Total nitrogen (N) loss and ammonia volatilization from urea applied to flooded rice grown on a paddy soil in Zhejiang Province were measured by 15N balance and micro-meteorological methods, respectively. Floodwater properties and ammonia loss from the circular plot were compared with those from the microplots. And the effectiveness of urease inhibitor, NBPT [N-(n-butyl) thiophosphonc triamide], was also tested Results showed that the total losses from urea broadcast and incorporated at transplanting (basal dressing) were similar with those from urea broadcast 12 days after transplanting (top-dressing) (51.5% and 48%, respectively, of applied N), and ammonia losses were low, the corresponding figures were 10.8% and 7.0% of applied N, respectively. Thus, denitrification was a much more important pathway of nitrogen loss than ammonia volatilization under the particular conditions. Addition of NBPT retarded urea hydrolysis, reduced pHs and ammoniacal nitrogen concentrations of floodwater for either the application of urea as basal or as top-dressing, but these effects were not translated into the reduction of total nitrogen loss. Floodwater pHs and ammonia loss in the microplots were apparently lower than those in the circular plot from urea applied as basal dressing; however, such differences were not found when urea was top-dressed. The frequently raining days occurred after top-dressing may be responsible for the insignificant effect of plot size on floodwater pHs and ammonia volatilization. It seems that the effects of plot size on floodwater properties and ammonia loss mainly depend on weather conditions, in addition to the height and leaf area index of the crop.
