Evaluation of tropical pasture species as leys in the semi-arid tropics of northern Australia

Abstract

Testing of pasture plants as leys in the semiarid tropics of northern Australia has been limited. Characteristics of successful ley pasture plants are discussed. The most important characteristic is the ability to contribute nitrogen to subsequent crops, which has been demonstrated for a number of legumes but not for grasses. Over 2300 legume and grass introductions have been evaluated as permanent pastures. Of the genera which are adapted to the environment of northern Australia, 14 grass cultivars (including Brachiaria, Cenchrus and Digitaria spp.) and 11 legume cultivars (including Aeschynomene, Centrosema and Stylosanthes spp.) are productive and are currently recommended for use as permanent pasture plants. Field experiments and commercial practice have shown that Centrosema pascuorum (cvv. Bundey, Cavalcade) is well adapted for use as a ley pasture plant. Other legumes which are suitable for use in leys are Alysicarpus vaginalis, Chamaecrista rotundifolia cv. Wynn, Macroptilium gracile cv. Maldonado and Stylosanthes hamata cvv. Amiga and Verano. The grasses are generally not suitable for ley pastures as they are strong perennials which are difficult to control in cropping areas. The exception is Urochloa mosambicensis which may be suitable as a break crop to control broadleaf weeds such as Sida acuta, Senna obtusifolia and Hyptis suaveolens. This species can be controlled with economic rates of herbicide and has seed dormancy characteristics which allow it to regenerate following a cropping phase.