The response of Lolium multiflorum (Lam.) to applied phosphorus and potassium on a cricket pitch clay

Abstract

Lolium multiflorum cv. Barmultra was used to evaluate the P and K status of plants grown on a smectitic soil commonly used for the construction of cricket pitches in the coastal regions of South Africa. Bulli was treated with P and K and, following treatment, soil test levels for P ranged between 2 and 28.5 mg L^-1 and for K between 109.5 and 480.5 mg L^-1. The amount of P required per unit increase in soil P test value declined sharply as the P application rate increased but the relationship between K applied and soil K test was linear. Plant yield increased asymptotically with increasing soil P level, whereas the response to K was significantly quadratic although relatively small. There was a significant yield interaction between soil P and soil K, with response to K being more marked at high than at low P levels. Potassium addition had a much greater effect on nutrient levels in plant tissue than did P addition but both significantly affected not only the P and K levels in the herbage material, but also the levels of other plant nutrients. In particular, there was a strong negative relationship between soil K and plant Na and a weaker negative relationship between soil P and plant Mg.