Crop rotation and residue management effects under no till on the soil quality of a Haplic Cambisol in Alice, Eastern Cape, South Africa

Abstract

Improvement and maintenance of soil quality is critical in achieving environmental and agricultural sustainability. Conservation agriculture (CA) technologies are widely reported to improve soil quality of arable soils in the long term. The objective of this study was to investigate and quantify the effects of crop rotations and residue management under no till on the soil quality of a Haplic Cambisol in Alice, Eastern Cape, South Africa. The study made use of plots from a CA field trial laid out in a split-plot design. The main plots were crop rotations viz maize-fallow-maize (MFM), maize-fallow-soybean (MFS); maize-wheat-maize (MWM) and maize-wheat-soybean (MWS). The sub-plots were allocated to residue management viz residue removal (R−) and residue retention (R+). The Soil Management Assessment Framework (SMAF) was used to evaluate the changes in soil quality after three years of CA treatment application. Soil organic carbon (SOC), microbial biomass carbon (MBC), β‑glucosidase (BG) activity, extractable P and K, soil pH, electrical conductivity (EC), bulk density (ρb) and aggregate stability (AGS) were measured and used in the calculation of the SMAF soil quality index (SQI) which was used as an indicator of soil quality. Crop rotations significantly (p < 0.05) influenced mineral N, soil respiration (CO2-C) as well as micro-nutrients Zn, Mn and Cu. Crop residue retention significantly (p < 0.05) improved soil organic C, microbial biomass C, soil respiration (CO2-C), mineral N, extractable P and K, Ca, Mg, Zn, Fe, Cu, Mn, EC and AGS. The study revealed the significance of crop residue management effects on the SQI score, while crop rotation and the interaction of crop rotation and residue management had no significant effects. Our study findings indicated that the SMAF was an effective monitoring tool for assessing soil and crop management effects on the soil quality of the South African Haplic Cambisol and possibly other soils.