Land Condition in the Tropical Tallgrass Pasture Lands. 1. Effects on Herbage Production.

Abstract

A quantitative condition index based on vegetation (botanical composition and basal area of perennial grasses) and soil characteristics (erodibility, nutrient status and availability, partitioning of rainfall into infiltration and run-off) was developed for tropical tallgrass pastures near Charters Towers (north-east Queensland) and Katherine (Northern Territory). Herbage growth and the responses of individual species at 10 sites over two growing seasons were related to the index. At all sites there were significant linear relationships between herbage growth and condition index although the values differed between sites. Annual grasses increased and most perennial grasses decreased as condition declined but Bothriochloa pertusa and Bothriochloa ewartiana were most abundant at intermediate condition levels. The response of Chrysopogon fallax varied widely between sites. The lower herbage production on poor condition sites will result in lower carrying capacity.