Long-term stocking rate effects on soil physical properties

Abstract

Summary. The effects of sheep stocking rate on soil physical properties were investigated in a long-term (>30-year-old) grazing trial on the Northern Tablelands of New South Wales. The soil physical properties studied were unsaturated hydraulic conductivity, soil strength and bulk density. Significant differences between the ungrazed and grazed pastures were found for all soil physical measurements. Compaction by sheep was limited to the upper 5 cm of the soil profile and resulted in lower porosity, mainly due to loss of pores larger than 1.2 mm equivalent diameter.

However, after 30 years, the pastures grazed at 10, 15 and 20 sheep/ha had similar soil physical properties. Soil physical properties appear to be relatively insensitive to stocking rate in the long term and therefore other factors, such as maintenance of pasture cover, should be given a higher priority in grazing management decisions.