Effect of rain water harvesting and drip irrigation on crop performance in an arid and semi-arid environment
Rainwater harvesting and drip irrigation are possible interventions to enhance crop performance in Arid and Semi-Arid Lands (ASAL). Work was undertaken to evaluate the feasibility of rainwater harvesting for bean production under an ASAL environment in Kaiti Watershed, Makueni District, Kenya. Treatments comprised two rainwater harvesting methods, Zai pits and contour ridges; bucket-kit drip irrigation and a control. No intervention was made to enhance water availability in the crop root zone in the control. The experiment was arranged in a Randomized Complete Block Design with three replicates. Each of the 12 experimental plots was planted with beans (Phaseolus vulgaris L.), variety GLP 2. Soil moisture content and pan evaporation were measured daily for 100 days and runoff after every rainfall event. Crop height was measured once a week and grain and biomass yield were determined at the end of the growing season. Soil moisture content and crop performance were significantly influenced by drip irrigation but not by rainwater harvesting. In drip irrigated plots, grain and biomass yield, were 4 tonnes ha-1 and 9 tonnes ha-1 respectively compared to 3.5 tonnes ha-1 and 7.5 tonnes ha-1 respectively, in the control plots. Drip irrigation effectively maintained adequate soil moisture resulting in better crop performance while rain water harvesting methods failed to significantly enhance soil moisture content and crop performance. This study indicated that rainwater harvesting makes a difference in runoff when the 14 Day Antecedent Precipitation (14DAP) exceeds 80 mm. However, the grain yield obtained in all the plots was higher than the national average of 0.36 tonnes Ha-1. It is recommended that further research be done under different rainfall conditions to confirm the conditions under which the benefits of rainwater harvesting using contour ridges and zai pits can be realized in the enhancement of crop performance in ASAL conditions.
Key words: ASAL, soil moisture content, Phaseolus vulgaris L, Zai pits, contour ridges drip irrigation, rainwater harvesting