Phosphate response of mixed swards, at Mt. Cotton, south-eastern Queensland

Abstract

Five levels of calcium dihydrogen phosphate were applied on a red-yellow podzolic soil to plots either unsown or sown to Kazungula setaria together with greenleaf desmodium, lotonis, stylo, or siratro. First season pasture yields varied from 2000 to 7400 lb an acre. Volunteer species and lotononis swards reached maximum yields at lower phosphate levels than the remaining legumes, which continued to respond at 80 lb P an acre. Maximum setaria yield occurred at 40 lb P an acre. Increasing phosphate level reduced nitrogen concentration of non-legumes, increased phosphorus concentration of all species, and substantially increased nitrogen yield of legumes (1.0-1.9 lb nitrogen response per lb P applied). Seasonal yield patterns and competitive interactions are discussed.