Tropical Grasslands (2007) Volume 41, 139–153

Why restore marginal cropland to permanent pasture? Land resource and environmental issues

D. MARK SILBURN, J. BRETT ROBINSON AND DAVID M. FREEBAIRN

Natural Resources & Water (Qld), Agricultural Production Systems Research Unit, Toowoomba, Queensland, Australia

Abstract

Soil physical and chemical degradation associated with cropping has resulted in reduced economic and environmental performance. This degradation of soil resources occurs slowly, but insidiously, and the effects may be hidden by variability in climatic and economic cycles. Permanent pasture or pasture-ley systems are important options available as alternative enterprises or as part of an ameliorative strategy. Addition of a pasture phase in a cropping system needs to explicitly recognise the soil properties that need to be improved, which may include surface or subsurface structure, nitrogen availability, organic carbon accumulation, or ephemeral soil surface conditions (cover, fracture of restrictive layers, surface storage). Benefits to soil physical condition developed under pasture are fragile and easily destroyed by tillage, wheel traffic and animal traffic and grazing. The benefits are best retained, when cropping is reintroduced, by using minimum tillage, stubble retention and controlled traffic, and by optimising fertility and crop productivity.
Pasture systems are inherently more efficient in using rainfall (they result in less runoff and deep drainage) than cropping, but the economics are dependent on relative prices of commodities and climatic conditions at a given time. In areas of high salinity risk, pastures have an important role in reducing deep drainage, although the placement of different land uses needs to consider salt stores and water pathways. The change in deep drainage when cropping is replaced with pasture is greatest on lighter-textured or shallow soils with lower plant available water capacity, giving considerably more reduction in the volume of recharge per unit area of pasture established.

Download full article (164 KB PDF)  

  Return to Contributed Articles