Estimation of the year-to-year variations in nitrate leaching in different soils and regions of England and Wales

A model has been used to estimate the losses of N by leaching from arable soils throughout England and Wales during winter and spring. It is predicted that the extent to which autumn residues of nitrate are leached by winter rains varies considerably from year to year and from site to site, and that this variation will cause much bigger differences in the N fertilizer requirements of deep-rooted crops than of shallow-rooted ones. It is estimated that an average of about 42% of the N applied as fertilizer is leached from arable soils in England and Wales each year. However, the resulting increase in the average nitrate concentration in the drainage water is estimated to exceed 11.3 μg N/ml only in the Eastern region. Spring leaching of freshly-applied N fertilizer is likely to be generally small, and will have little effect on the N fertilizer requirements of deep-rooted crops, but may affect those of shallow-rooted crops in the west.