No abstract

The results of field and laboratory studies of solute transport through undisturbed soils following narrow pulse or step-change inputs of soluble salts or bacteria were analyzed using the transfer function equation developed in paper 1 (Jury et al., this issue) of this series. The travel time probability density function observed for Br and C1 during unsteady flow in an unsaturated, well structured clay suggested a two-component mechanism comprising fast solute transport through large, interped voids and slow to negligible transport through small, intraped voids. The modal and median travel times varied with soil type, initial water content, and rate of water input. The fractional volume of water that participated in solute transport, 0st, was calculated from the rate of water input and the median solute travel time.Values of 0st ranged from 14% to nearly 90% of the mean volumetric water contents (0)of the soils.

Abstract. Losses of nitrogen in the tile drainflow from a clay soil (Evesham series) under grazed grassland were monitored during the 1982/83 and 1983/84 drainflow seasons. In 1982/83, 40% of the discharge had a NO3− concentration > 11.3 mgNl−1, while in 1983/84 concentrations were always > 20 mgNl−1. Total N lost by leaching was 17.5 and 48.7 kg ha−1 in 1982/83 and 1983/84 respectively, which was equivalent to 9 and 43% of the fertilizer applied. The marked difference in N losses for the two seasons was attributed to differences in the quantity and timing of N fertilizer applications, the dryness of the preceding summer and the duration and density of stocking.