Sheep camping influences soil properties and pasture production in an acidic soil of New South Wales, Australia

Abstract

This paper reports sheep camping influences on soil chemical and physical properties, and pasture dry matter (DM) production of an acidic soil on the southwest slopes of New South Wales, Australia. The experiment was conducted in the spring (October-November) of 2005 on a long-term field experimental site after 13 yr of rotational grazing. The factors considered were sheep camping (distance from the camping site), pasture type (perennial vs. annual pastures) and lime application (limed vs. unlimed treatments). Over 13 yr of rotational grazing, significant amounts of carbon (C), nitrogen (N), phosphorus (P) and potassium (K) were deposited near the sheep camping site via the deposition of animal excreta. Total C increased from 32.8 g kg-1 20 m away from the camping site to 41.9 g kg-1 at the camping site in 0-5 cm soil depth. The Colwell P increased from 44.0 to 125.9 mg kg-1 from the non-camping area to the camping site in 0-5 cm soil depth. The most interesting result from the current study is that soil bulk density decreased as the intensity of camping increased. On the perennial pastures, soil bulk density was 0.96 and 1.34 g cm-3 at the camping site in the 0-5 and 5-10 cm soil depths, respectively, whereas soil bulk density was 1.14 and 1.39 g cm-3 at 20 m away from the camping site at the corresponding soil depths. Across pasture types, mean pasture DM was highest at the camping site (7.3 and 6.6 t ha-1 for the limed and unlimed pastures, respectively), and lowest 20 m away from the camping site (5.4 and 4.5 t ha-1 for the limed and unlimed pastures, respectively). The vigorous pasture growth and high organic matter at the camping site may have had a "cushioning effect", thereby reducing soil compaction. However, this camping effect was confined to within 5 m of the camping site. It is concluded that sheep camping can create spatial heterogeneity in soil chemical and physical properties. The non-uniform influence on pasture productivity and composition could be minimised by altering the grazing management strategies, such as periodic relocation of the site of shelter, or further subdivision of the grazing paddock, if necessary. Key words: Soil carbon, nitrogen, phosphorus, bulk density, grazing management