OBSERVATIONS ON THE RELATIONSHIP BETWEEN SOIL FERTILITY, PASTURE BOTANICAL COMPOSITION, AND PASTURE GROWTH RATE; FOR A NORTH ISLAND LOWLAND PASTURE

Abstract

Soil chemical fertility, pasture composition and pasture production data were collected for seven 'microsites' within two farmlets at Massey University's No. 1 sheep farm. Palmerston North. The two farmlets had been maintained for twenty years at stocking rates of 26 and 16 su/ha, and were found to have gradients (presumed to result from sheep grazing and camping behaviour) of increasing soil fertility away from a road and towards a shelterbelt. Microsites were placed along these gradients to include contrasting fertility levels for the two stocking rates. Mean values for soil pH, Olsen P and 'quicktest' K tiller density for the various pasture species and pasture production at each of the seven microsites are presented. A microsite where Olsen P = 109 was barley grass dominant and produced 10.5 t DM/ha/year. For other microsites ryegrass tillers per m2 increased with P and stocking rate; and white clover and sweet vernal growing points/tillers per m2 decreased with increasing P. Production ranged from 9.9 t DM/ha/year where Olsen P = 14 to 19.1 t DM/ha/year with different seasonal timing where Olsen P = 66.