Pasture studies on the coastal lowlands of Subtropical Queensland. III. The nutrient requirements and potentialities of Desmodium uncinatum and white clover on a lateritic podzolic soil

Abstract

Nutrient deficiencies in a lateritic podzolio soil typical of the eucalypt ridges of the coastal lowlands of south-eastern Queensland, as measured by the responses of Desmodium uncinatum (Jacq.) DC, and white clover (Trifolium repens L.), are reported and discussed. The soil is grossly deficient in phosphorus and nitrogen; other severely limiting nutrients are calcium, copper, sulphur, and, somewhat later in growth, potassium. Molybdenum and zinc are less limiting to growth, but additions of them may be needed as pastures become older. It is possible that boron may also be i11 short supply for some species. White clover responded well to additions of copper, but Desmodium did not. It would also appear that white clover requires more calcium than D. uncinatum. The results for this soil are in general agreement with those obtained on the gley soils in the region. The two soils are sufficiently different in their water relations for white clover to thrive on the gleys (wet soils) and to be short-lived on the podzolic (dry) soils where it is subject to attack by nematodes. D. uncinatum shows promise as a pasture legume on both soil types. This is the first recorded use of D. uncinatum as a pasture legume under field conditions. The results quoted are from ungrazed trials; however, in other experiments D. uncinatum has been maintained under intermittent and at times very close grazing by sheep. Yields of approximately 2 tons of dry matter/acre/year have been obtained once this species is well established. The nitrogen content of the material is 3.2–3.6 per cent. These figures indicate that this species, which has persisted for up to 4 years on each soil type, can be made a valuable component of subtropical coastal pastures.