Sensitivity of selected chemical and biological soil quality parameters to tillage and rotational cover cropping at the Zanyokwe Irrigation Scheme, South Africa

Abstract

Sustainable management of soils requires knowledge of the impact of agronomic practices such as tillage and crop rotation on soil quality. The objective of this study was to identify soil chemical and biological soil attributes with high sensitivity to tillage and rotational cover cropping practices on two sandy clay loam soils, a Bonheim at Burnshill and a Shortlands at Lenye, in the Zanyokwe Irrigation Scheme, Eastern Cape, South Africa. Treatments were no tillage, conventional tillage and three crop rotations involving maize–fallow–maize, maize–wheat–maize and maize–oat–maize. Principal component analysis was used to isolate the soil chemical and biological parameters that were most altered by tillage and crop rotations, while hierarchical cluster analysis was used to discriminate the crop rotation effects. Results showed that soil microbial biomass nitrogen, mineralisable nitrogen, and extractable phosphorus were the properties most altered by tillage and crop rotations. The soil properties that were most sensitive to tillage and crop rotations were those most influenced by organic matter inputs. The maize–wheat–maize and maize–oat– maize rotations were clustered together, indicating the similarity of their positive impact on soil quality.

Keywords:

• conservation agriculture
• hierarchical cluster analysis
• organic matter
• principal component analysis
• soil health