LONG-TERM STOCKING RATE EFFECTS ON SOIL PHYSICAL-PROPERTIES

The effects of sheep stocking rate on soil physical properties were in vestigated in a long-term (>30-year-old) grazing trial on the Northern Tablelands of New South Wales. The soil physical properties studied w ere unsaturated hydraulic conductivity, soil strength and bulk density . Significant differences between the ungrazed and grazed pastures wer e found for all soil physical measurements. Compaction by sheep was li mited to the upper 5 cm of the soil profile and resulted in lower poro sity, mainly due to loss of pores larger than 1.2 mm equivalent diamet er. However, after 30 years, the pastures grazed at 10, 15 and 20 shee p/ha had similar soil physical properties. Soil physical properties ap pear to be relatively insensitive to stocking rate in the long term an d therefore other factors, such as maintenance of pasture cover, shoul d be given a higher priority in grazing management decisions.