Optimal Soil Moisture Depletion Levels for the Production of Vernonia (Vernonia galamensis L.) and it’s Effect on Growth, Yield and Yield Components

Abstract

The field experiment was carried out at Wondo Genet Agricultural Research Center 07°03’19’’ to 07°04’00’’ N latitude and 38°30’08’’ to 38°31’02’ E longitude during 2015/16 dry season. The experiments were arranged in a randomized complete block design with three replications. Seven soil moisture depletion levels (30, 40, 50, 60, 70, 80 and 100% of the total available water of the soil) were used. The result indicated that different soil moisture depletion levels had very highly significant (p<0.001) effect on days to flowering, days to seed set, days to maturity, plant height, number of branches per plant, number of capsules per plant, thousand seed weight and seed yield. It was also affected oil yield highly significantly (p<0.01). Moreover, different soil moisture depletion levels significantly (p<0.05) influenced water use efficiency. However, different soil moisture depletion levels showed no significant difference in the oil content of Vernonia. Vernonia grown under 100% SMDL took a shorter number of days to 50% flowering, days to seed setting and days to maturity. On the other hand, 30% SMDL took the longest days to flowering, seed setting and days to maturity. The maximum plant height, number of branches per plant and number of capsule per plant were 162.7 cm, 150 and 196.8 at 30% SMDL, respectively. The highest seed yield (2213 kg ha-1) and oil yield (711.8 kg ha-1) were obtained at 60% soil moisture depletion level. However, the highest water use efficiency based on oil yield (0.15 kg/m3) was obtained at 100% SMDL irrigation is set when soil moisture content touches PWP. Thus, the optimal seed yield, oil yield and WUE could be achieved when 493.4 mm seasonal net irrigation depth of water applied with scheduling at 60% SMDL for the production of Vernonia at Wondo Genet and similar agro-ecological areas.