A comparison of nutrient losses following grassland improvement using two different techniques in an upland area of mid‐Wales

Abstract
Water samples from ditches draining small upland areas in mid‐Wales were collected before, during and after the improvement of the pasture using two different cultivation techniques. The samples were analysed for nitrogen, phosphorus, potassium and pH. The greatest release was associated with disc harrowing where nitrogen, in its nitrate form, exceeded European Economic Community maximum recommended concentrations for potable water supply for two weeks. Smaller losses of nitrogen, in the ammonium form, and of ortho‐phosphate were observed following a minimum cultivation technique. It is concluded that, on a scale normally associated with upland Britain, pasture improvement is not likely to deteriorate significantly the quality of runoff within water supply catchments. This is confirmed by the results obtained from monitoring streamflow from catchments in which some degree of pasture improvement had been undertaken in the past.