New Zealand agriculture is primarily dependent on the growth of high producing pastures which rely on legumes for their nitrogen supply. Legumes under favourable conditions are able to fix large amounts of nitrogen by virtue of the nodule bacteria attached to their roots. Nitrogen is supplied to grasses by underground transference, after the needs of the host plant are satisfied and is also provided in the urine and dung of grazing animals. Almost invariably poor pasture growth in New Zealand is the result of low legume production. Contributing factors to this are a poor supply of available phosphorus, sulphur, molybdenum and potassium, ineffective nodulation and acid soil conditions. The key then 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 widespread, probably due to low atmospheric returns. The different zones of tussock country in Central Otago have been reviewed previously by the author (Ludecke (1960)). The aim of tussock country improvement in Central Otago is two-fold. Firstly to improve pastoral production both by increasing stock performance (i.e. increasing wool weights and lambing percentages, decreasing death rates, rearing fat lambs) and increasing sheep and cattle numbers; secondly to improve the lower country so that the grazing pressure can be eased on the higher snowgrass country, where soil and water-conservation is vital for irrigation and hydro-electric schemes. It is only in the last five to ten years, since the control of rabbits and development of aerial topdressing and oversowing that farmers have been able to take advantage of research finding on run-country improvement. The purpose of this study is to determine what kinds and quantities of fertilizers should be applied to the different soils in the tussock grassland regions of Central Otago in order to obtain maximum legume growth. This necessitated classifying the soils in the area, laying down field trials and measuring the responses to sulphur and phosphorus, and correlating these responses with soil chemical data. Trials will be reviewed which were laid down to assess the production that can be obtained by oversowing and topdressing fescue tussock country. Studies will be made on the accumulation of organic matter in these oversown and topdressed soils.