Responses of legumes to phosphorus and sulphur fertilisers on 2 toposequences of North Otago soils, New Zealand

Abstract Field trials were established on 2 North Otago toposequences to determine the patterns of sulphur (S) and phosphorus (P) deficiency, and to compare the effectiveness of agricultural grade elemental S (100% S), ‘molten-mix’ S-super-phosphate (MMSS, 27% S) and superphosphate (10% S) for establishment and growth of legumebased pastures over 3 years. S deficiency was severe at all sites. P deficiency ranged from nil to moderate on yellow-grey earths and was severe on yellow-brown earths. On yellow-grey earths, superphosphate and MMSS were markedly superior to agricultural grade elemental S as sources of S for plants. A minimum application rate of 200 kg/ha MMSS is suggested for legume establishment, on the basis of economic and agronomic criteria. Mean herbage production was much less on yellow-brown earths than on yellow-grey earths. The differences in effectiveness of the fertilisers for supplying S on the yellow-brown earths were not clear. Very high P applications were required to achieve maximum...