摘要
Ceramic cup samplers were used to measure nitrate leaching from grass/clover pasture in Wales to which no N fertilizer had been applied and from a predominantly grass pasture receiving 100 kg fertilizer-N/ha annually. Annual leaching losses at individual sampling points, measured over a 3-year period between 1988 and 1991, ranged from the equivalent of < 0·1 to 226 kg N/ha. All data sets were positively skewed and in four out of six cases conformed to a log-normal distribution. The marked spatial heterogeneity was attributed to the uneven deposition of N in the excreta of grazing stock but variations in soil depth and hydrology may also have contributed. Particularly large losses occurred from those areas of the plots where sheep congregated. As a result of this heterogeneity, there were large standard errors associated with estimates of mean losses from the pastures as a whole. Overall losses ranged from 13 to 24 kg N/ha per year from grass/clover plots and from 10 to 13 kg/ha from fertilized grass plots. There was no consistent relationship between relative losses from the two types of pasture. The quantity of nitrate leached appeared to be independent of stocking rate, although there was a direct correspondence between the loss from grass/clover plots and the proportion of clover in the sward. Estimates of nitrate concentrations in drainage never exceeded 5·6 mg N/I for either sward.
摘要译文
lers用于测量威尔士草坪/三叶草牧场的硝酸盐淋失，其中没有施用氮肥，而且主要是草牧场每年接收100公斤肥料-N /公顷。在1988年至1991年的3年期间，每个采样点的年浸出损失范围为相当于0.1·226 kg N / ha。所有数据集均呈正偏态，六个案例中有四个符合对数正态分布。显着的空间异质性归因于放牧种群排泄物中N的不均匀沉积，但土壤深度和水文的变化也可能有所贡献。绵羊聚集的地块的那些区域发生了特别大的损失。由于这种异质性，与整个牧场的平均损失估计相关的标准误差很大。草/苜蓿地块每年总损失为13至24千克N /公顷，受精草地每年损失10至13公斤/公顷。两种牧场的相对损失之间没有一致的关系。浸出的硝酸盐量似乎与放养率无关，虽然草/三叶草地块的损失与草地上的三叶草比例之间存在直接对应关系。对于任一种草坪，排水中硝酸盐浓度的估计值从未超过5·6 mg N / I.
S. P. Cuttle (a1); M. Hallard (a1); E. K. Gill (a1);R. V. Scurlock (a1). Nitrate leaching from sheep-grazed upland pastures in Wales[J]. The Journal of Agricultural Science, 1996,127(3): 365-375