Effect of conservation agriculture on selected soil physical properties on a haplic cambisol in Alice, Eastern Cape, South Africa

Conservation agriculture (CA) is believed to contribute to sustainable crop production. However, there are contrasting reports on its short-term effects on soil properties. An experiment was conducted to determine the effects of CA on bulk density (BD), porosity, mean weight diameter (MWD) and penetration resistance (PR) in a semiarid province of South Africa (SA). A split-split-plot design was used; the main treatment factor was allocated to tillage [(Conventional Tillage (CT) and No-Till (NT)], sub-factor of crop rotation [(Maize-Fallow- Maize (MFM), Maize-Oat-Maize (MOM and Maize-Vetch-Maize (MVM))] and sub-sub factor of residue management [(retention (R+); removal (R-) and biochar (B)]. No-tillage, significantly increased soil organic carbon (SOC) compared to CT at the 0-5 cm depth. Tillage, crop rotation and residue management significantly (P < 0.01) affected MWD at the 0-5 cm depth, but not (p > 0.05) on BD, porosity and PR. The lack of significant differences, in both NT and CT plots, between biochar applications and residue retention with respect to BD, MWD across seasons and PR, also show that biochar can potentially be used as a crop residue strategy in a CA system. However, there is a need to further tests and also explore the biochar crop residue retention combinations.