Distribution of potassium in the soil profile of a sandplain soil under pasture species

Abstract

The influence of pasture species and pasture/crop rotations on the fate of K fertilizer in the soil profile of a sandplain soil was investigated. Results for Lupinus cosentinii, subterranean clover and a subterranean clover/wheat rotation are presented. Potassium was applied as KCl at six rates up to 150 kg K ha^-1 for three years; bicarbonate-extractable K was measured at five depths in the profile (0–100 cm) for four years. The net change in available K in the top 100 cm of the profile (kg ha^-1) was calculated. There was a gradual increase in K down the profile under all species with fertilizer application. The increase was largest for L. cosentinii, which also appeared to redistribute K from below 100 cm to the soil surface. The K residual value on this soil type was higher than expected with most of the fertilizer applied over three years being retained in the top 100 cm.