Effect of soil management on water deficit, gas exchange and cowpea yield in the semi-arid region

Rainfall variability in semi-arid areas often results in water shortages during the cycle of the cowpea (Vigna unguiculata (L.) Walp.), affecting yield. This study aimed to investigate the effect of different management practices on soil water deficit, leaf gas exchange and the yield of the cowpea under rainfed conditions in a semi-arid region. The experimental design was completely randomised into split lots of five management systems (treatments) and two layers of soil (0.15 and 0.30 m), with four replications. The management systems investigated were: T-P, soil turned by hoe only; T-ESC, ploughing to 0.30 m only; T-CS, soil with subsoiling and in situ catchment; T-CCM, subsoiling, in situ catchment and mulch, and T-CCO, subsoiling, in situ catchment, mulch and compost. The results showed that the interaction of the practices of mulching, composting, subsoiling and in situ catchment, resulted in the T-CCO having a greater capacity to capture and store water in the soil, with a consequent increase in water availability for the crops. This fact increased the yield of T-CCO in relation to the other treatments by (1st to 4th) 41%, 28%, 47% and 12%. For a water deficit generated after ten consecutive days without rain, the T-CCO displayed the best results in maintaining the physiological state of the plants. However, when the soil was close to field capacity, there were no significant differences for soil management practice in stomatal conductance, photosynthesis, transpiration or leaf temperature. This fact demonstrates the importance of soil management under limiting conditions of moisture.