“Low-Hanging Fruit” Practices for Improving Water Productivity of Rainfed Potatoes Using Integration of Cultivar Selection, Mulch Application, and Different Agroecological Zones in Sub-Tropical, Semi-Arid Regions

Unevenly distributed rainfall leads to reduced potato water productivity (WP) under rainfed production conditions. Understanding the practices that can increase WP is vital. Our objectives were to understand (i) the seasonal variables that influence WP under rainfed conditions and (ii) the effect of the integration of cultivar x locality x mulch on potato WP. The study was undertaken in smallholder settings in two agroecological zones: Appelsbosch (Mbalenhle locality) and Swayimane (Stezi and Mbhava locality). A split plot, in a randomized complete block design experiment, included mulching (mulch and no mulch), four selected cultivars, and s three localities. Soil water content (SWC), yield, and climatic data were collected, and actual crop evapotranspiration (ETa) and WP were calculated. Rainfall, ETa, and crop growth and development had a significant influence on the seasonal WP. Cultivar × mulch × locality had an insignificant effect on the WP, however, locality × cultivar significantly altered the WP. The localities that had lower vapor pressure deficit (VPD), high relative humidity, and sandy soil had a higher potato WP for all cultivars, with the highest (18.38 kg m−3) being that from Electra. The findings suggest that using localities that have less atmospheric dryness and a cultivar (Electra) that shows stability of yield across the seasons can be an easy-to-apply practice for increasing potato WP in a resource-limited environment.