The interaction of lime and phosphorus on the nodulation and growth of white clover

The effect of lime, monocalcium phosphate, and copper sulphate on the nociulation and growth of white clover ( Trifolium repens ) on a strongly leached yellow‐brown earth of pH 4.9 was investigated by pot trials. Nodulation and yield of clover dry matter were increased at all levels of phosphorus by increasing lime from 0 to 10 cwt per acre. Increasing lime to 40 or 160 cwt per acre reduced the nodulation and yield of clover at levels of phosphorus from 14–84 lb per acre. In Trial 1 the reduced nodulation and yield at 160 cwt lime was restored by increasing phosphorus to 180 lb per acre; but in Trial 2 adding 168 lb phosphorus increased the yield at 40 cwt of lime, but had little effect at 160 cwt per acre. The percent phosphorus in the clover dry matter decreased as lime was increased from 0 to 160 cwt per acre. The total uptake of phosphorus increased as lime was increased from 0 to 10 cwt because of the large increase in clover dry matter, but decreased as lime was increased from 10 to 160 cwt. As the depression in yield at high rates of lime was accompanied by a reduction in both percent phosphorus in the clover and total uptake of phosphorus, it appears that lime depresses clover yield by reducing the plant uptake of phosphorus. Copper had no effect on the yield of clover.