PERFORMANCE OF ELEMENTAL SULPHUR, SULPHUR-SUPERPHOSPHATE AND SUPERPHOSPHATE ON DRY INLAND SOUTH ISLAND HILL COUNTRY

Abstract

Four trials were established on sunny and shady slopes at two altitudes in Sdeficient dry inland hill country in North Otago, to compare the effectiveness of three commercial S fertilisers - elemental S, "wet-mix" S-superphosphate, and superphosphate - during the legume establishment phase of pasture development. The effects of single initial applications of these fertilisers were followed by harvesting legumes over three years. All sites were severely deficient in S but showed variable response to P; no P responses being recorded on the steeper, higher altitude sites. In terms of DM response per kg S applied superphosphate was slightly more effective than S-superphosphate and both were markedly more effective than elemental S over the 3- year period. Aspect had little or no influence on relative P and S requirements or fertiliser effectiveness. Responses to elemental S were approximately linear up to 100 kg S/ha, and application of lesser rates of elemental S are not recommended. On the basis of DM produced per weight of applied fertiliser, "wet-mix" S-superphosphate was superior to superphosphate, and about 200 kg/ha S-superphosphate is suggested as a minimum initial application rate for legume introduction on these soils (yellow-grey earths). An initial dressing at this rate maintained around 70% of potential yield over the 3 year trial period. Keywords: elemental S, Ssuperphosphate, hill soils, yellow-grey earths, legume establishment, fertiliser, sulphur