Effect of water stress at different growth stages on growth and productivity of faba bean (Vicia faba L.)

Response of two faba bean (Vicia faba L.) cultivars: viz H sub(72) and BB7 to water stress was studied by subjecting the crop to stress duration for 24 days(withholding irrigation) during vegetative S sub (1), flowering or pod set S sub(2), and pod filling stage S sub(3), in a field experiment conducted for two successive seasons at Hudieba Research Station Farm during 1998/99 and 1999/2000. The different treatments were arranged in a factorial randomized complete block design. Expansive growth attributes, reproductive structures production and abscission pattern, and crop phenology were examined. Biological yield (t/ha), harvest index, seed yield (t/ha) and yield components were monitored during the two seasons and were a dversely a ffected by the water-stress treatments. Soil moisture content, actual and potential daily evapotranspiration, and crop coeffocoent values for the different stages of crop growth were monitored. Water used efficiency (WUE) was also calculated. Results proved that the phase of pod set was found to be more sensitive to drought, followed by pod filling and the vegetative phase, as shown by the greater reductions in growth attributes, seed yield and yield components and water use efficiency. Mild water stress during flowering followed by sufficient irrigation of water after flowering resulted in slightly increased seed yield, greater WUE and harvest index. However, the continuous 12-day irrigated crop had resulted in a significant increase in the expansive and reproductive structures, produced and induced significant increases in seed yield, yield components and WUE. Soil moisture content was maintained at relatively higher levels under frequent watering in the top 30 cm of the soil profile. The infrared thermometer calibration with the gravimetric method and Penman's modified equation were found to be well-suited to monitor faba bean water stress, as its measurements (i.e. canopy temperature difference) were strongly correlated with the acual and potential evapotranspiration