Movement of sulphate sulphur in soils as influenced by certain fertiliser treatments : University of New Zealand thesis presented for the Degree of Master of Agricultural Science (Honours)

Abstract

The economic policy of New Zealand must surely be directed towards the maintenance of a continued increasing level of output of primary produce, and to achieve this, more marginal land must be developed. In the South Island there is an area of 12 million acres of tussock grassland - an area of inherent and induced low soil fertility - in fact, marginal land awaiting development.

Field and laboratory studies have revealed that the low soil fertility can often be attributed to certain plant nutrient deficiencies. Generally, nitrogen deficiency is widespread, and because under New Zealand conditions it is too expensive to apply this fertiliser out of the bag, pasture improvement programmes usually incur the introduction of a legume into the sward. However, unless the nutrient requirements of legumes are fully satisfied, they will not fix adequate nitrogen for their companion species. Research undertaken to ascertain these nutrient requirements on many tussock soils has shown an interesting pattern of soil deficiencies of sulphur, phosphorus, and certain trace elements.

Sulphur deficiency has been recorded to be widespread - a reason attributed to the low returns of atmospheric sulphur with the rainfall. Data from field trials containing various sulphur fertiliser treatments has indicated that residual responses often occur. It is the purpose of this thesis to investigate some reactions of the sulphate ion in the soil, and thus explain the residual effects of sulphur fertilisers .