Soil quality characteristics of kikuyu-ryegrass pastures in South Africa

- A soil quality index was developed specifically for pasture systems in South Africa.
- The minimum data set was selected using principal component analyses.
- The index included physical, chemical and biological indicators.

Development of a soil quality index for kikuyu (Pennisetum clandestinum)-ryegrasss (Lolium spp.) pasture systems in the southern Cape of South Africa is important since there are certain warning signs that their sustainability is being threatened. A total of 142 pastures throughout the region were sampled and several soil physical, chemical and biological indicators were quantified. A minimum data set of the most sensitive indicators was chosen using principal component analyses. Linear scoring functions for these indicators were used to develop a soil quality index. The most sensitive indicators were: extractable P > gravel content > water holding capacity (WHC) > exchangeable acidity (EA) > soil organic matter (SOM) = penetration resistance (PR) > exchangeable Mn. The soil quality index (SQI) was equated as: SQI = 0.13 (PR) + 0.16 (Gravel) + 0.15 (WHC) + 0.14 (EA) + 0.17 (P) + 0.12 (Mn) + 0.13 (SOM). This soil quality index is appropriate for pasture systems in the southern Cape of South Africa, and may be useful for similar pasture systems in other areas.