EVALUATION OF WATER PRODUCTIVITY FOR VINE PRODUCTION OF ORANGE-FLESHED SWEET POTATO (Ipomoea batatas (L.) Lam.) UNDER DIFFERENT SUPPLEMENTARY IRRIGATION TECHNIQUES AND FERTILIZER APPLICATION IN EAST MAMPRUSI DISTRICT

Abstract

Orange-Fleshed Sweet Potato (Ipomoea batatas (L.) Lam.) is a climate-resilient crop with significant potential for improving food security and livelihoods in semi-arid regions. However, its productivity is often limited by water scarcity and soil nutrient deficiencies. Despite its importance, limited research has been conducted on the combined effects of supplementary irrigation techniques and fertilizer application on vine production and water productivity. This study evaluated the performance of orange-fleshed sweet potato under three supplementary irrigation techniques-drip, rain tube, and furrow irrigation -combined with fertilizer application in the East Mamprusi District. A split-plot experimental design was used, with irrigation technique as the main plot factor and fertilizer application (with and without) as the subplot factor. The experiment consisted of six treatment combinations, replicated three times, making a total of eighteen experimental units. Each plot measured 5 m × 10 m, with a planting density of 33,333 plants per hectare. Supplementary irrigation was applied based on the estimated crop water requirement of 412 mm for the growing season. The hydraulic performance of the irrigation systems showed emitter flow variations of 58.2 % and 61.5 % for drip and rain tube, respectively, indicating poor performance. However, the uniformity coefficients were rated as good, at 82.4% for drip and 78.6% for rain tube. In evaluating the performance of the drip and rain tube irrigation system used on the study site, the ratings were assigned according to ASAE (1999). The emitter flow variation for drip and rain tube irrigation systems was 23.6 % and 30.8 %, respectively, both classified as poor. The uniformity coefficient was 90.45% for drip and 89.76 % for rain tube, rated as very good. Field emission uniformity was 85 % for drip and 81% for rain tube, both rated as good. The coefficient variation was 0.11 for drip (fair) and 0.15 for rain tube (poor), indicating moderate variability in water distribution. The highest vine yield (1.36 ton/ha) and dry above ground biomass (5.51 ton/ha) were recorded under drip irrigation with fertilizer, whereas the lowest yield (0.73 ton/ha) and above- ground biomass (3.12 ton/ha) was observed under rainfed conditions without fertilizer. Water productivity (WPET) followed a similar trend, with drip irrigation and fertilizer yielding 1.49 kg/m³, while rainfed conditions without fertilizer recorded 0.81 kg/m³. Canopy cover varied significantly, with the highest observed cover (90%) under drip and rain tube irrigation with fertilizer, while rainfed conditions without fertilizer had the lowest (56%). Water use efficiency (WUE) was highest under drip irrigation (2.22 kg/ha/mm), followed by rain tube (1.92 kg/ha/mm), furrow (1.75 kg/ha/mm), and rainfed conditions (1.53 kg/ha/mm). Findings indicate that supplementary irrigation, particularly drip irrigation with fertilizer, enhances vine yield and water productivity. However, rain tube irrigation presents a viable alternative due to its relatively lower cost. This study provides insights for optimizing irrigation strategies in semi-arid environments and serves as a valuable reference for policymakers, researchers, and extension officers promoting climate-smart agricultural practices. The adoption of climate-smart supplementary irrigation techniques with fertilizer support is recommended to improve water productivity and ensure sustainable orange-fleshed sweet potato production.