UPTAKE OF PHOSPHORUS FROM DIFFERENT SOURCES BY LOTUS-PEDUNCULATUS AND3 GENOTYPES OF TRIFOLIUM-REPENS .1. PLANT-YIELD AND PHOSPHATE EFFICIENCY

The breeding of phosphate (P) efficient pastoral legumes could reduce the amount of fertiliser required on pastoral farms. In this study, Lo tus pedunculatus and 3 genotypes of white clover (Trifolium repens L.) known to differ in their ability to respond to added P were grown on unfertilised soil and soil to which either monocalcium phosphate (MCP) or North Carolina phosphate rock (NCPR) were added. White clover geno type 8D (a selection line from Crau) had a greater (P < 0.05) internal P efficiency (shoot DM production per unit plant P) than 1A (a select ion line from Gwenda) or lotus on unfertilised soil, whereas on fertil ised soil, lotus had a significantly higher (P < 0.05) internal P effi ciency than 2 of the white clover genotypes on MCP-fertilised soil (P < 0.01) and all 3 white clover genotypes on NCPR-fertlised soil (P < 0 .01). Lotus also had a higher (P < 0.01) external P efficiency (total P uptake) than all 3 white clover genotypes on the 2 fertilised treatm ents. This was due to a greater root length, not a greater P uptake pe r unit length.