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 amongst many graziers in Australia and elsewhere in the world. 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 in a sheep grazing property of Currajong in south east region of Queensland, Australia where the two grazing systems of continuous and TC grazing were compared. Results obtained on the impact of grazing management on soil characteristics over a five-year period (2001 - 2006) showed an increase in soil organic carbon (SOC) and nitrogen (SON) in the areas with favorable soil condition over the study period as 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 higher grass growth occurring under TC grazing, which in turn decreases the contamination potential for downstream water bodies. This reduction was much more pronounced on a historical sheep aggregation camp turned into TC system, where a large amount of fecal materials had been deposited prior to the its convertion to TC grazing. The smaller size of the paddocks along with the long rest period provided by TC grazing in this area recognized to be the major contributors to both physical and chemical recovery of the soil after each grazing operation.