The impact of grazing systems on soil properties and pasture production

Abstract

The new system of "cell grazing" or "time control grazing", involving short intensive grazing followed by a long period of rest, has become popular amongst graziers; however, little is known about its long-term impact on soil or its ability to produce pasture in a sustainable manner. This paper reports on the results of a study carried out on a large grazing property in the Traprock region of Queensland where the two grazing systems, conventional and cell grazing, were compared and the influence of the two systems on soil properties and grass production was studied. Results show an increase in total soil organic carbon and nitrogen level under cell grazing compared to continuous grazing. The concentrations of soluble phosphorus and nitrogen in runoff and soil extracts were reduced under cell grazing, possibly due to the increased plant growth and higher rate of uptake of soluble nutrients under cell grazing compared to the conventional grazing system. This higher nutrient uptake achieved under cell grazing also decreased the potential for downstream water quality contamination. The long rest period provided by cell grazing system together with a more uniform animal distribution over the confined cells appears to have positively contributed to both physical and chemical recovery of the soil after each round of grazing. Such a recovery under cell grazing contributed to increased herbage mass and higher productivity of the grazing lands. The presence of a higher quantities of litter and above ground organic materials on lands under cell grazing reduced hoof pressure on the soil underneath and reduced compaction. The smaller size of the paddocks in cell grazing also contributed to a more even distribution of animals in the cell, a lower overall trampling opportunity and a reduced rate of soil damage by compaction. Continuous grazing allows grazing animals to selectively graze patches of the pasture with more palatable grass varieties and congregate in camp sites. Both of these actions contributed to un-even distribution of trampling, animal dropping and plant residue, which resulted in further compaction and degradation of soils of these sections of the paddock and less chance for plant species to re-grow.