Effect of Intercropping Maize and Sunn Hemp at Different Times and Stand Densities on Soil Properties and Crop Yield under In-Field Rainwater Harvesting (IRWH) Tillage in Semi-Arid South Africa

Evidence suggests that manipulating intercropping timing and stand density within intercropping systems could enhance crop yields. However, our current understanding of the effects of intercropping a cover crop on soil chemical properties and moisture still needs to be improved. This study investigates the effects of intercropping sunn hemp with maize at different timings and stand densities on selected soil properties and crop yield. A split-plot experiment was conducted under the in-field rainwater harvesting (IRWH) tillage. The trial had three intercropping times (simultaneously with maize planting, at V15 maize growth stage, and R1 maize growth stage) as the main plot factors and three stand densities (16, 32, and 48 plants m−2) as the subplot factors, with three replicates for both the 2019/20 and 2020/21 seasons. Changes in soil properties were assessed within the uppermost layer (0-30 cm). Soil moisture content was continuously monitored throughout the growing season and specific soil chemical properties were analyzed at harvest. The results showed that the interaction of sunn hemp intercropping period and stand densities did not significantly influence most of the measured soil properties. The early planting of sunn hemp had significantly 32.4