DROUGHT-TOLERANT TRAITS IN WINTER LEGUME COVER CROPS UNDER DIFFERENT WATER REGIMES IN SEMI-ARID CONDITIONS

Climate change and water scarcity pose a threat to current crop productivity. Considering that Limpopo is a dry area, it will be hard to increase crop productivity under the continuous decline in rainfall resulting from climate change. It is vital to understand the impact of water stress on crop production in order to improve crops' ability to adapt to water stress in the future. To explore their potential under water-limited conditions, a study was conducted in Limpopo to assess the drought tolerance of four winter legume cover crops, i.e., pea, lupin, clover and vetch, in terms of key drought-tolerance traits, including the leaf area index, shoot biomass production, leaf gas exchange processes such as transpiration, stomatal conductance, intercellular CO₂ concentration, the photosynthetic rate and soil carbon dioxide emission rates. The experiment was carried out with a split-plot design, with the main factor being the winter legume—pea (Pisum sativum), lupin (Lupinus albus), clover (Trifolium spp.) or hairy vetch (Vicia villosa)—and the sub-factor being one of two irrigation regimes (well-watered and water stress). The results reveal that all cover crops performed better in well-watered conditions, with significantly higher shoot and root biomass than in water-stressed plots. Increased biomass had a positive effect on the shoot-to-root ratio, suggesting good adaptability to irrigation regimens. Although transpiration rates were elevated in well-watered treatment groups, stomatal conductance, transpiration, and photosynthetic rates did not differ significantly between the irrigation treatments. These findings highlight the resilience of these legume cover crops and suggest their potential for sustainable integration into dry-land farming systems, especially under future climate uncertainty.