Short-term effects of conservation agriculture strategies on the soil quality of a Haplic Plinthosol in Eastern Cape, South Africa

Abstract

The improvement of soil quality in agro-ecosystems is one of the major objectives of conservation agriculture (CA) strategies. The objective of this study was to evaluate, quantify and compare the effects of two tillage practices, four crop rotation sequences, two residue management systems and their interactions on the soil quality of a Haplic Plinthosol in South Africa using the Soil Management Assessment Framework (SMAF). The evaluation was done on a CA field trial established in 2012 in the Eastern Cape Province of South Africa. The trial was laid out in a split-split-plot design with tillage: conventional tillage (CT) and no-till (NT) as main plot treatments. Sub-treatments were crop rotations: maize-fallow-maize (MFM); maize-fallow-soybean (MFS); maize-wheat-maize (MWM); maize-wheat-soybean (MWS). Residue management treatments: removal (R-) and retention (R+) were in the sub-sub plots. Soils from the CA trial were sampled at 0 – 5 and 5 – 10 cm depths after five cropping seasons (2012–2015). Thirteen soil quality indicators were determined to assess soil quality. The SMAF soil quality index (SMAF-SQI) was used as an indicator of overall soil quality. The study results demonstrated the dominance of tillage practices in significantly affecting soil biological, chemical and physical properties in the short term than crop rotation sequences and residue management systems. The soil biological indicators viz. SOC, MBC and BG activity were more sensitive to CA strategies, which confirmed their effectiveness as tools for soil quality assessments in the short-term. The study also revealed the short-term significant effects of tillage on the overall SMAF-SQI while crop rotation and residue management had no significant effects. Overall soil quality assessment using the SMAF technique provided a sound basis for distinguishing the short-term impacts of CA strategies on the function of the Haplic Plinthosol in Eastern Cape, South Africa.