Tillage and Crop Rotation Effects on Selected Soil Chemical Properties and Wheat Yield in a Sandy Loam Oakleaf Soil in the Eastern Cape, South Africa

The effects of tillage and crop rotation on soil selected chemical properties and wheat yield were evaluated during the 6th season of an on-going field trial at the University of Fort Hare Farm (UFH), South Africa. Two tillage systems; conventional tillage (CT) and no-till and crop rotations; maize (Zea mays L.)-fallow-maize (MFM), maize-fallow-soybean (Glycine max L.)-(MFS); maize-wheat (Triticum aestivum L.)-maize (MWM) and maize-wheat-soybean (MWS), were evaluated. Residues were retained in all treatments after each cropping season. No-till resulted in significantly higher soil organic carbon (SOC), ammonium-N (NH4-N), nitrate-N (NO3-N), P, K, Ca and Zn relative to CT. The MWS rotation recorded significantly higher SOC while the MFM rotation had the least SOC under both tillage treatments. Tillage and crop rotation effects were not significant (p > 0.05) with regards to grain yield in all the seasons. Generally, higher wheat grain yield was found in the MWS rotation under no-till. Soil organic carbon, P and total mineral N were positively correlated with grain yield. It is concluded that, in the long term, regular inclusion of soybean in rotation coupled with surface residue retention under no-till is expected to have a positive significant impact on soil health and wheat grain yield. (C) 2019 Friends Science Publishers