The effect of phosphorus, potassium, and calcium on the growth, chemical composition, and symptoms of deficiency of white clover in a subtropical environment

Abstract

The effect of the rates of application of sodium phosphate, potassium chloride, and calcium carbonate on growth, chemical composition, and visual symptoms of deficiency in Trifolium repens var. Irrigation White, grown in a low humic gley soil under subtropical conditions in Queensland, has been investigated. The surface soil is grossly deficient in phosphorus, potassium, and calcium and consists almost entirely of sand (92 per cent.). Additions of sodium phosphate, potassium chloride, and calcium carbonate each increased the yield of clover, increased the phosphorus, potassium, and calcium contents respectively, and conditioned the uptake of other nutrients. Plant material for chemical analyses consisted of petioles and leaves (less senescent and expanding leaves), harvested at the immediate pre-flowering stage of growth. Critical percentages for phosphorus, potassium, and calcium under these conditions were established at 0.23, 1.1, and 1.0 per cent. respectively. Visual symptoms of phosphorus, potassium, and calcium deficiencies are discussed in relation to yield and nutrient content. The sum of the equivalents of potassium, calcium, and magnesium is approximately constant. The mean value of 18 analyses covering all treatments was 136 m-equiv. per cent. with a range of 116-148.