Effect of Rainwater Harvesting Technology on Cowpea Yield in the Savannah Belt of Nigeria
This study investigated the effects of two rainwater harvesting (RWH) technologies (micro) and macro-catchments) on cowpea yield in the savannah belt of Nigeria with a view to identifying the better technology that could mitigate against adverse effects of erratic rainfall. The study was carried out in Afikuyomi village (between latitude 7° 45' N and longitude 4° 10' E) 10km north of Iwo town (Osun state) in the derived savannah belt of Nigeria. In the micro catchments RWH, both the runoff producing area (RPA) and runoff receiving area (RRA) lie typically within a single farmland while in the macro catchment system, the two areas (RPA) and RRA) do not lie within a single farmland. The micro catchment plot has a slope of 2° and four treatments: RWH, Semi-circular bunds (SCB), Semi-circular bunds with RWH (SCB+RWH) and the control plot. The experimental layout was completely randomized with three replicates of each treatment. Each of the four sub plots measured 7m x 5m. The macro catchment plot was made up of four treatments: Double soil manipulation (DSM) with RWH (DSM+RWH), Single soil manipulation (SSM) with RWH (SSM+RWH), Zero tillage (ZT) with RWH (ZT+RWH) and the control plot laid out in complete randomized design with two replicates. Each of the four sub-plots measured 5m x 5m. Plant and soil parameters were measured fortnightly during the growing period. At maturity, yield and its components were determined. The results showed that in the micro catchment plot, the average soil moisture content were 10.95%, 10.08%, 8.90% and 7.69% in the SCB+RWH, RWH, SCB and control treatments respectively at 0-15cm,15-30cm and 30-45cm depths. The highest crop yield of 0.47t/ha and 1.55/ha dry matter were obtained for the SCB+RWH treatment compared to 0.31t/ha and 1.18t/ha for the control. Furthermore, the SCB treatment had the highest water use efficiency value of 7.7okg/hacm-1 compared with 6.09kg/hacm for the RWH p<0.05). In the macro plot, DSM+RWH gave the least soil penetration resistance of 6.8N and bulk density of 1.50g/cm3 compared with 30.75N and 1.61 g/cm3 for the control treatment. Also, the highest crop yield of 1.84t/ha, 3.3t/ha dry matter and 26.52kg/ha cm-1 water use efficiency (P<0.05) were obtained for DSM+RWH compared with 0.78t/ha and 2.64t/ha for the control and 13.0kg/hacm-1 water use efficiency for the ZT+RWH treatment. The results showed that cowpea yield can be increased using either micro-catchment RWH with Semi-circular bunds (RWH+SCB) or Macro catchment RWH with double soil manipulation (RWH+DSM).