LIME AND PHOSPHORUS REQUIREMENTS FOR HILL COUNTRY YELLOW-BROWN EARTHS

Three fertiliser trials on hill country yellow-brown earths are discussed, The results show that on a newly sown ryegrass (Lolium perenne) white clover (Trifolium repens) Pasture 90% maximum pasture production was achieved at an Olsen P level of 13-15 ppm. On a reverted browntop (Agrostis tenuisl pasture an Olsen P concentration of at least 25 ppm was required for 90% maximum production. Reasons for this difference are discussed. Liming increased pasture dry matter production on all sites and the largest increases in production occurred at low (1.25 t/ha) rates. There was no evidence that liming enhanced P availability and therefore lime and P requirements for these soils should be considered independantly. Phosphorus applications generally increased legume production but the effects of lime were variable. On the Mahoenui soil liming increased grass growth at the expense of the legume component but on the Marua soils liming increased the legume content. An explanation for this is suggested. The practical implications of these results are discussed.