Natural recovery of soil physical properties from treading damage of pastoral soils in New Zealand and Australia: A review

This paper reviews natural recovery of deteriorated soil physical condition under animal treading in grazed pastoral systems, particularly in New Zealand and Australia. While much research has focused on soil compaction and physical deterioration from animal treading, there has been much less focus on natural recovery of soil physical properties after treading damage has occurred. Natural recovery of deteriorated soil physical condition improves soil properties including hydraulic conductivity, macropore volume and bulk density. Soil physical condition naturally recovers when animals are partially or completely excluded from pasture, although improvements are likely to be limited to no deeper than 10–15 cm soil depth, under common grazing practice or animal exclusion. However, the physical deterioration and natural recovery processes are linked in a cycle. Natural recovery of soil physical condition in this cycle is therefore important when evaluating management practices affecting soil deterioration on-farm, field trial interpretation, and ungrazed riparian zone soil structure. This review also discusses directions of future research to enhance soil management, including quantifying and evaluating soil physical deterioration and natural recovery. Several knowledge gaps relating to pastoral agriculture in New Zealand and Australia, particularly under rotational grazing management on intensive dairy farms are discussed. Further research is required into the consequences of farm management practices that enhance natural rejuvenation of degraded soils. Consequently, integration of both deterioration and natural recovery of soil physical condition in the soil compaction and recovery cycle is needed to improve farm system evaluation and management. Natural recovery of soil condition when animals are partially or fully excluded from grazing is therefore important in management and modelling of pastoral and ungrazed riparian soil, and subsequent environmental impacts.