The Influence of tree shade on soil attributes, water storage and microclimate in Robusta coffee grown in a rainfall gradient of the mid-altitude zone of Central Uganda

Robusta coffee ( Coffea canephora ) is a key economic crop in the mid-altitude zone of central Uganda whose cultivation is expanding to marginal areas with variable rainfall, high temperatures, humidity variation, reduced soil moisture, and low soil physical and chemical attributes, which are increasingly threatening its sustainable production. This study investigated the influence of tree shade on soil attributes, microclimate regulation, and soil water storage in Robusta coffee plots across rainfall gradients within the mid-altitude zone of central Uganda. A nested field experiment was conducted in 20 by 20-meter de-alienated coffee plots across three categorised thresholds (low (< 1100 mm year-1), moderate (1100–1200 mm year ^− 1 ), and high (> 1200 mm year ^− 1 ) in central Uganda. The treatments included six shaded and unshaded coffee plots per rainfall threshold. Results indicated that tree shade significantly improved soil physical and chemical attributes, particularly organic matter and cation exchange capacity, resulting in enhanced soil health. Tree shade moderated microclimate conditions by reducing the maximum air temperature by 0.78°C and increasing the maximum and minimum relative humidity by 1.02% and 0.56%, respectively. Shade increased the average volumetric soil moisture content at 10cm by 0.28mm and 1.47mm at 50cm profile levels. The benefits of shade were pronounced in high rainfall and shaded plots. The study, therefore, concludes that integrating shade in Robusta coffee improves soil attributes, buffers microclimate extremes, and enhances soil moisture storage in marginal areas. The Results indicate the potential of tree shade as a climate adaptation strategy in sustainable Robusta coffee production amidst rainfall variability.