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
Laboratory incubation experiment was conducted to study the effect of lime nitrogen(LN) on transfor-mation of iirea-N in three paddy soils. The results showed that LN had an inhibitory effect on urease activityin thes...Laboratory incubation experiment was conducted to study the effect of lime nitrogen(LN) on transfor-mation of iirea-N in three paddy soils. The results showed that LN had an inhibitory effect on urease activityin these soils especially in the first 5 days, and that in the first 20 days of incubation, the amount of NH-Nderived from urea was lower in the soil with LN than in the soil without LN. While after 30 days the ainountof NH-N was higher in the mature haplic paddy soil developed on Quaternary red clay(MHPS) with LNthan that in the soil without LN. The amonnt of NH_3-N volatilized was decreased in the earlier stage andincreased in the later stage of incubation in the MHPS by the addition of LN.展开更多
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.
文摘Laboratory incubation experiment was conducted to study the effect of lime nitrogen(LN) on transfor-mation of iirea-N in three paddy soils. The results showed that LN had an inhibitory effect on urease activityin these soils especially in the first 5 days, and that in the first 20 days of incubation, the amount of NH-Nderived from urea was lower in the soil with LN than in the soil without LN. While after 30 days the ainountof NH-N was higher in the mature haplic paddy soil developed on Quaternary red clay(MHPS) with LNthan that in the soil without LN. The amonnt of NH_3-N volatilized was decreased in the earlier stage andincreased in the later stage of incubation in the MHPS by the addition of LN.
