Further Aspects of Sulphur Nutrition of Legumes

THE KEY to improving the native tussock grasslands of the South Island is to obtain good legume growth. In these areas, the main nutrient deficiencies which limit the growth of legumes are sulphur, phosphorus and molybdenum. Sulphur deficiencies are very widespread (Walker et al., 195.5; Lobb and Bennetts, 1958; McLeod, 1961). The manner in which a rational fertilizer programme was formulated for the dryland areas of Central Otago has been described elsewhere (Ludecke, 1960, 1962a, 1962b). With the exception of a small area of very dry soils, all soils in Central Otago are extremely sulphur deficient and vary in their phosphate requirements; as the rainfall increases and the soils become more leached, the responses to phosphate in the presence of sulphur increase. The recognition of widespread sulphur deficiencies in Central Otago and the formulation of a rational fertilizer programme has been of tremendous economic significance to the economy of Otago. On a Wanaka property on which 1,200 acres of tussock country have been improved by aerial oversowing and topdressing, the wool weight in Merino hoggets has been raised in a period of two years from 4.10 lb per head to 7.25 lb per head. This result has been obtained for the expenditure of E3 per acre. On this property, where the soils are extremely sulphur responsive and only slight phosphate responses are obtained, the farmer applies 1 I/z cwt of sulphurized super-phosphate (400 lb mixture) and 2 lb white clover, 2 lb Montgomery red clover, 1 lb alsike clover and 2 lb cocksfoot per acre. This is the cheapest land development in New Zealand. In trials to be reviewed in this paper, it has been found that the fineness of grinding of elemental sulphur is very important and the residual effects of gypsum are greater than those from fine or coarse sulphur.