CRITICAL PHOSPHORUS CONCENTRATIONS FOR BURR MEDIC, YELLOW SERRADELLA, SUBTERRANEAN CLOVER, AND WHEAT

The relationship between plant yield and the phosphorus (P) concentration in dried tops and seed of burr medic (Medicago polymorpha), yellow serradella (Ornithopus compressus), subterranean clover (Trifolium subterraneum), and wheat (Triticum aestivum) was determined, and critical P, which is the P concentration in tissue that is related to 90% of the maximum yield of each species at each harvest, was interpolated. Critical P data are limited for subterranean clover and wheat, which are widely grown in south-western Australia. There are no critical P data for burr medic and yellow senadella, two new pasture legumes. For each species, critical P varied, often markedly, for different experiments. For all species, (i) critical P in dried tops generally decreased with increasing maturity, (ii) critical P was larger for seed than dried tops near maturity.