Effect of Drought Stress and Vermicompost Amendment on Some Physiological Growth Indices and Yield of Green Bean (Phaseolus vulgaris L.)

In order to study the physiological growth indices and yield of green bean in response to vermicompost amendment under drought stress conditions a field experiment was conducted in Dezful, southwest of Iran during 2016 using a split plot design in a randomized complete block design with four replications. Application of drought stress by irrigation interval method at four levels of irrigation (irrigation after 100, 140, 180 and 220 mm evaporation from class A evaporation pan) as the main factor and 0, 4, 8 and 12 tons ha-1 of vermicompost were considered as a sub factor. With intensifying drought stress from 140 to 220 mm evaporation from the evaporation pan, maximum values of dry matter of the plant, leaf area index, plant growth rate and durability of the leaf area significantly decreased. Except for the relative growth rate which was less affected by vermicompost, increasing the application of vermicompost from 4 to 12 tons ha-1 caused a great increase in the remaining physiological growth indices compared to control treatment. Interaction of drought stress and vermicompost on all traits was not significant except for green pod yield. The vermicompost – related increase in yield of green bean in drought stress conditions (21%) was higher than the increase in favorable conditions (16%). The highest and lowest correlations with yield were related to dry matter of the plant (r=0.97**) and relative growth rate (r=-0.27). In general, the results showed that vermicompost application under stress and non-stress conditions improved the physiological growth indices and hence the yield of the green pod and could be recommended for green bean production in the area.