Short-term tillage management effects on grain sorghum growth, yield and selected properties of sandy soil in a sub-tropical climate, South Africa

Abstract

Poor soil fertility and water holding capacity, coupled with climate change, threaten smallholder agriculture under dryland conditions, particularly in sandy soils. The resilience of sorghum makes it an ideal candidate crop for conservation agriculture (CA), under these conditions, but its productivity and effectiveness could depend on the cultivar used, planting time, tillage, and rotation. This study determined the effects of these factors on selected soil properties, growth and grain yield of two sorghum cultivars in sandy soils, under semi-arid conditions. The trial was conducted between 2019 and 2022 on a sandy soil with <10 % clay and <1.0 % carbon, at Clau-Clau village in Mpumalanga province, South Africa. The experiment had a randomized complete block design (RCBD) set up, in a strip-split-split-plot treatment structure with three replications. The treatment factors were tillage (conventional tillage (CT) and no-till (NT)), planting date (early and late), and rotation (with cowpea or sorghum monoculture) and sorghum cultivar (Pan 8816 and Macia). In the second growing season, early planted sorghum outperformed the late planted crop, with 44.4 % greater height and 36.1 % higher 1000-seed weight. Furthermore, the grain yield (1.33 and 0.56 t/ha, respectively) and dry matter yield (2.38 and 1.10 t/ha, respectively) were significantly higher for early than late planting in season 2. The NT treatment had significantly higher SOC, available P and exchangeable K than CT treatment in season 2. In season 3, early planting had 30.4 % higher exchangeable K than late planting, while NT increased total N and SOC by 50 and 34.8 %, respectively than CT. The findings of this study show the positive effects of early planting and NT on sorghum grain and dry matter yields, while effects on soil properties were greater during the season with higher rainfall, with no effects of cultivar and rotation on this infertile sandy soil.