Comparing the effects of continuous and time-controlled grazing systems on soil characteristics in Southeast Queensland

摘要

Grazing by livestock has a great influence on soil characteristics with major effects on soil carbon and nitrogen cycling in grazing lands. Grazing practices affect soil properties in different ways depending on the prescribed stocking rate and grazing periods. The new grazing system of short, intensive grazing followed by a long period of rest, referred to as time-controlled grazing (TC grazing), has become popular among many graziers in Australia and elsewhere. However, little research has been carried out on the impacts of this grazing system on the physical and chemical health of the soil. To address this issue, a comprehensive field study was carried out on a sheep-grazing property in the south-eastern region of Queensland, Australia, where the 2 grazing systems of continuous and TC grazing were compared. Results over the period 2001-2006 showed an increase in soil organic carbon and nitrogen in the areas with favourable soil condition compared with continuous grazing. There was also an increase in ground-litter accumulation over time and no compaction in TC grazing. Nitrate and extractable P concentrations were reduced by increased grass growth under TC grazing, which in turn decreased the contamination potential for downstream water bodies. This reduction was much more pronounced on a historical sheep aggregation camp, where a large amount of faecal material had been deposited prior to conversion to TC grazing. The smaller size of the paddocks, along with the long rest period provided by TC grazing in this area, are recognised to be the major contributors to both physical and chemical recovery of the soil after each grazing operation.