Experimental Evaluation of Conservation Agriculture with Drip Irrigation for Water Productivity in Sub-Saharan Africa

Abstract

A field-scale experimental study was conducted in Sub-Saharan Africa (Ethiopia and Ghana) to examine the effects of conservation agriculture (CA) with drip irrigation system on water productivity in vegetable home gardens. CA here refers to minimum soil disturbance (no-till), year-round organic mulch cover, and diverse cropping in the rotation. A total of 28 farmers (13 farmers in Ethiopia and 15 farmers in Ghana) participated in this experiment. The experimental setup was a paired ‘t’ design on a 100 m2 plot; where half of the plot was assigned to CA and the other half to conventional tillage (CT), both under drip irrigation system. Irrigation water use and crop yield were monitored for three seasons in Ethiopia and one season in Ghana for vegetable production including garlic, onion, cabbage, tomato, and sweet potato. Irrigation water use was substantially lower under CA, 18% to 45.6%, with a substantial increase in crop yields, 9% to about two-fold, when compared with CT practice for the various vegetables. Crop yields and irrigation water uses were combined into one metric, water productivity, for the statistical analysis on the effect of CA with drip irrigation system. One-tailed paired ‘t’ test statistical analysis was used to examine if the mean water productivity in CA is higher than that of CT. Water productivity was found to be significantly improved (α = 0.05) under the CA practice; 100%, 120%, 222%, 33%, and 49% for garlic, onion, tomato, cabbage, and sweet potato respectively. This could be due to the improvement of soil quality and structure due to CA practice, adding nutrients to the soil and sticking soil particles together (increase soil aggregates). Irrigation water productivity for tomato under CA (5.17 kg m−3 in CA as compared to 1.61 kg m−3 in CT) is found to be highest when compared to water productivity for the other vegetables. The mulch cover provided protection for the tomatoes from direct contact with the soil and minimized the chances of soil-borne diseases. Adapting to CA practices with drip irrigation in vegetable home gardens is, therefore, a feasible strategy to improve water use efficiency, and to intensify crop yield, which directly contributes towards the sustainability of livelihoods of smallholder farmers in the region.