Establishing Baseline Values for Soil Quality Indicators in the Southern Cape of South Africa

Commercial dairy farming on pasture is commonly practiced in the southern Cape region of South Africa. In terms of its sustainability, quantification of the impact of dairy-pasture management on soil quality is essential. To comprehend the behaviour of soils in terms of quality, indicators should be assessed to screen the general direction of soil quality within a management system. Development of a soil quality assessment framework necessitates establishment of baseline values for soil quality indicators. The aim of this study was to establish baseline values for soil quality indicators for dairy-pasture soils in the southern Cape. Physical, chemical and biological indicators on a no-till kikuyu (Pennisetum clandestinum)-ryegrass (Lolium spp.) pasture were compared to those of a virgin soil. Stratification ratios, which demonstrated the rate at which the indicator decreased with depth, were assessed for soil organic matter (SOM) related indicators. Biological indicators showed a well-established and well-functioning microbial population in the improved pasture soil. Stratification ratios demonstrated that the soil quality of the improved pasture system was improved relative to the virgin soil. Chemical indicators showed that the impact of nutrient management was favourable to pasture productivity. The association between the chemical and biological indicator were better established in the managed pasture. Physical indicators demonstrated that management practices adversely impacted the ability of the soil to provide physical support and structural functionality. This data were used in developing a first approximation of baseline values. Further research is warranted to validate them on representative commercial dairy farms in the southern Cape