Influence of agricultural land use and management practices on selected soil properties of a semi-arid savanna environment in South Africa

• Land use and management practices reduced soil quality.
• Tillage contributed the formation of a plough pan layer.
• Soil organic matter was negatively affected by agricultural management practices.

The contribution of agricultural land use and management practices to soil degradation was compared on land with: more than 20-years of natural grazing (NG), cultivation of horticultural (HC) and field (FC) crops, and undisturbed savanna (US) in South Africa. Tillage with tractors in the FC and HC plots resulted in greater soil compaction compared with NG and US systems. The soil under FC and HC had a greater percentage of micro-aggregates (<0.25 mm; 56.2% and 60.4%, respectively) than NG (16.1%) or US (22.7%). The aggregates in FC were the least water stable followed by that of HC, NG and US. Soil water content was significantly higher (p < 0.05) in soil from HC (3.46%) than NG (2.13%), US (1.67%) or FC (0.87%). Soil compaction was greater in the profile of the FC, NG and HC than US. Grazing and cultivation significantly reduced soil organic matter and microbial biomass carbon. Both organic and microbial biomass carbon were significantly positively correlated with many soil properties. Overall, the study showed that both animal grazing and cultivation of crops significantly reduced soil physical and biological properties compared with undisturbed land. The results provide evidence that land management practices are an important component of sustainability in this dry savanna ecosystem.