Pasture harvested and dried to provide estimates of either standing dry matter (DM) or growth rate usually contains some soil contamination. Pasture samples are therefore usually washed in order to provide a reliable estimate of total DM. Although the effect of washing on soluble plant components has been studied for several species, there have been few measurements on pasture. Mixed-pasture samples were subjected to one of three levels of contamination by soil and each divided into three subsamples for random allocation to one of three washing treatments. Each pasture sample was subsequently dissected into ryegrass (Lolium perenne) and white clover (Trifolium repens) components before N, P, S, K, Na, Ca, and Mg analysis. Uncontaminated samples only were analysed for soluble sugar content. The percentage contamination of plant material by soil was determined by reference to the titanium (Ti) content of the soil used to contaminate the samples. Unwashed samples directly from the field contained minor contamination. Washing of these and/or induced ‘contaminated’ treatments reduced soil contamination to less than 2%. Induced soil contamination, which ranged from 10 to 48%, significantly depressed all major nutrient concentration levels, with the effect tending to be greater for white clover than ryegrass. The levels of soil contamination imposed in this experiment were higher than those present on most pasture samples. However, even a short period of washing in clean flowing water removed almost all contaminating soil and restored nutrient and soluble sugar levels to those measured in unwashed, uncontaminated pasture. There was no indication of any loss of measured soluble plant components by pasture washing.
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