Abstract:
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.
