Contour-Based Rainwater Harvesting and Integrated Nutrient Management for Improved Soil Fertility in Semi-Arid Zimbabwe

In the smallholder farming areas of Zimbabwe’s semi-arid regions, low and unreliable rainfall, coupled with poor soil fertility, severely limits crop production. These challenges have been exacerbated by climate change. This case study evaluates the effects of contour-based rainwater harvesting (RWH) techniques (tied contours (TC) and infiltration pits (IP)) compared with standard contours (STDC) combined with integrated nutrient management (INM) approaches on sandy soils. Field experiments conducted over three cropping seasons (2015–2018) in Marange demonstrated that RWH techniques significantly improved soil moisture retention, water use efficiency, and nutrient uptake. Fields with RWH had substantially higher maize yields (2210 kg ha −1 for TC and 1792 kg ha −1 for IP) compared to STDC (1176 kg ha −1 ). Combining RWH with cattle manure as basal fertilizer and varying levels of nitrogen application further enhanced soil productivity. During wet season, RWH systems provided significantly higher returns on investment compared to STDC. However, during drought years, reducing mineral fertilizer application proved advisable since limited rainwater was captured. This case demonstrates that contour-based RWH and INM offer sustainable agriculture. Smallholder farmers are recommended to adopt the use of tied contours and INM due to high WUE, NUE, crop yields and soil moisture content.