**4. Discussion**

#### *4.1. Evaluation of Solar MajiPumps*

On the specification of the MajiPumps, MP400 and MP200 would lift water up to 25 m (using 160 W 24VDC solar panel) and 10 m (using 80 W 12 VDC solar panel), respectively, both having 34 L/min open flow rate. During our field experiment, we observed that MP400 and MP200 pumps would lift water to a maximum of 18 m (using 200 W 24 VDC solar panel) and 10 m (using 150 W 12 VDS solar panels). The pipe maximum flow (3/4 inch in size) was found 24.6 L/min for MP400 with 200 W rigid panel and 22.4 L/min with a 150 W rigid panel. Various factors including solar intensity, panel types, and surrounding temperature could affect pump discharge head and discharge.

The minimum discharges from the shallow groundwater wells at the point of maximum discharge heads (i.e., 18 m, 14 m, and 10 m) were 7.8 L/min, 3 L/min, and 23.6 L/min, for MP400 with 200 W rigid panel, MP400 with 200 W flexible panel, and MP200 with 150 W rigid panel, respectively. This minimum pump discharges could fill the 1000 L water storage tanks that farmers used for this experiment in 2.1 hr., 5.6 hr., and 4.6 hr., respectively. When the solar MajiPumps (i.e., MP400 with 200 W rigid panel, MP400 with 200 W flexible panel and MP200 with 150 W rigid panel) provides the maximum water yield capacity (i.e., 24.61 L/min, 15 L/min, and 22.2 L/min), they could fill the 1000 L water storage tanks in 0.68 hr., 1.11 hr., and 0.75 hr., respectively. Considering 8-h effective solar intensity in a day, MP400 and MP200 pumps would lift a maximum of about 11,764 L/day and 10,666 L/day, respectively. This would help to provide irrigation between half and one hectare of land depending on crop types, farming systems, water application systems, and cropping season.

#### *4.2. Effects of CA on Water Productivity, and Crop Yields*

The water-saving capacity of CA was found significantly higher when compared to CT for the various irrigated vegetables and rainfed maize production. This was mainly due to a reduction of water loss from soil evaporation associated with the grass mulch cover in CA. Consequently, soil moisture would be maintained and available for crop use in the CA practice. Assefa et al. [28] found up to 49% reduction of evapotranspiration and up to 40% increment of soil moisture in CA practice for various vegetables, supporting the claim that reduction of water loss is mainly from reduced soil evaporation. Significant improvement of water productivity associated with CA practice was observed in the Ethiopian highlands [13,27,28]. CA was tested with drip irrigation previously [11,16,22, 25–28] showed a significant increase in water productivity. Similarly, in our study CA under both a drip irrigation system and overhead irrigation significantly increased water

productivity. Thus, farmers who could not afford to buy a drip irrigation system would still get a significant water-saving benefit from the use of CA, even with overhead irrigation.

Crop yield was found significantly higher in CA when compared to CT for the various irrigated vegetables and rainfed maize production. This was mainly due to an improvement in soil quality (nutrients) and water use efficiency in CA. Assefa, Jha, Reyes, Worqlul, Doro, and Tilahun [29] found more than 6% and 4% increment of soil organic C and total N, respectively, under CA when compared with CT. Besides, CA decreased nutrient loss due to either runoff or percolation. Belay et al. [26] found a significant decrease of NO3-N (up to 44%) and PO4-P (up to 50%) in runoff and leachate under CA as compared to CT. This provides more readily available nutrients in CA for plant growth, leading to improved crop yields. Crop yield improvements in CA for this study (15–170%) were found to be consistent with Assefa et al. [11] and Belay et al. [26], which showed 9% to more than 100% yield improvements in CA with the drip irrigation system. This indicates, CA would still provide a significant improvement of soil quality and crop yield regardless of the irrigation practice (overhead or drip system).
