Pasture production responses to fertiliser on renovated West Coast pakihi soils

Abstract

Mowing trials were carried out to determine the rates of fertiliser nitrogen (N), phosphorus (P), potassium (K) and sulphur (S) and frequency of application of K for maximum pasture production on extremely infertile humped and hollowed pakihi soils in the Grey Valley (Souters and Sommervilles dairy units), and flipped soils at Cape Foulwind (Bassetts dairy unit) under high annual rainfall (2000 - 3000 mm) on the West Coast. In the first measurement year, there was no significant increase in pasture production above 480 kg N/ha, 56 kg P/ha, 360 kg K/ha and 136 kg S/ha at Souters and Bassetts and a significant increase in pasture production up to 600 kg N/ha, 56 kg P/ha, 360 kg K/ha and 140 kg S/ha at Sommervilles. In the second year, there was no significant pasture production increase above 480 kg N/ ha, 56 kg P/ha, 360 kg K/ha and 136 kg S/ha at all sites. The high N, K and S rates were required because nutrients were not being recycled through returned clippings. This situation would be similar to the early stages of dairy management on these units where only a small proportion of pasture would receive recycled nutrients through return of excreta. Over time, a larger proportion of the pasture would be affected by excreta and fertiliser nutrient requirements would be expected to decrease. There was no increase in pasture production from applying potassium chloride in more than four applications per year at Souters and Bassetts in the first year, but a significant increase in pasture production from eight compared with four applications per year at Sommervilles, where soil QT (quick test) K levels were lower than at the other two sites. Keywords: flipped, hump and hollowed, nitrogen, phosphorus, potassium, sulphur