Studies on some deep sandy soils in Cape York Peninsula, North Queensland. 2. Plant nutrient status

Abstract

The nutrient status of the deep siliceous sands which cover an extensive area in Cape York Peninsula has been studied in glasshouse and field experiments. Using Townsville stylo (Stylosanthes humilis) as a test legume, the soils were found to be extremely deficient in P and S, and moderately so in Zn, Cu, and K. Responses to Mo were found on most of the eight soils tested in the glasshouse but these were not confirmed at the field site in either of the two growing seasons. There was little response to Ca (lime) in spite of the very low levels of total and exchangeable Ca in these soils. Suggested reasons for this are the known tolerance of tropical legumes to low Ca supply and the fact that exchangeable Ca, although low, represented a fairly high percentage of the total exchange capacity. Levels of total N in these soils were also very low and the native grasses were able to absorb only 15 kg N ha-1 in an entire growing season. Two samples of rock phosphate (from north-western Queensland and Christmas Island) were found to be very poor alternatives to superphosphate, at least in the first season. In spite of the extreme infertility of these soils, very high levels of pasture production (> 10,000 kg of Townsville sty10 ha-1) could be achieved in well-fertilized pastures.