EFFECTS OF WATER DEFICIT ON THE YIELD RESPONSES OF COMMON BEAN (Phaseolus Vulgaris L.) UNDER DRIP IRRIGATION SYSTEM IN MIZAN-AMAN SOUTHWEST, ETHIOPIA

Abstract

Deficit irrigation consists in deliberately applying irrigation depths smaller than those required to satisfy the crop water requirements, thus affecting evapotranspiration and yields, but keeping a positive return from the irrigated crop. Deficit irrigation with low cost drip irrigation system is likely to be widely adopted by small-scale farmers to apply irrigation water efficiently and economically. This experiment was conducted at Mizan Aman Southwest, Ethiopia to investigate the effect of deficit irrigation on water use efficiency and yield response of common bean (Phaseolus vulgaris L.) under drip irrigation system. Five level of irrigation water application were used as treatments in randomized complete block design with three replications. The first treatment T1 was 100% irrigation water application which was used as a control. The second, third, fourth and fifth treatments were given 80%, 60%, 40% and 20% irrigation water application respectively, as deficit irrigation treatments. Deficit irrigation practice was applied after the first growth stage and continued for the whole growth season. Data were collected on agronomic parameters, days to 50% emergence, days to 100% ground cover, days to 50% flowering, number of nodules per plant, number of branches per plant, plant height, number of pods per plant, number of seeds per pod and hundred seed weight to evaluate the effects of deficit irrigation water on yield, yield components and productivity of common bean; level of significance of P ≤ 0.05. The result showed that the highest yield was found under T1 (3.49 ton/ha). Applying 80% irrigation water application (T2), lead to saved 17.60% of the irrigation water and reduced the total yield by 10.13%,; applying 60 % irrigation water application (T3) lead to saved 35.21% of the irrigation water and reduced the total yield by 12.59%; applying 40 % irrigation water application (T4) lead to saved 52.81% of the irrigation water and reduced the total yield by 49.37% whereas applying 20% irrigation water application (T5) lead to saved 70.42% of the irrigation water which produced 31.58% of the total yield. The result showed that applying deficit irrigation water up to 40% (i.e. greater than 60% irrigation water application) during the growing season except first growth stage has no significant effect on productivity of common bean production but applying deficit irrigation water greater than this percent considerably reduced its productivity. Furthermore, it is recommended that these results are from only one season at one site; thus, such studies require to be repeated in space and time to put the recommendation on strong basis