DETERMINATION OF WATER TABLE CONTR IBUTION TO ACTUAL VAPOTRANSPIRATION FOR BREAD WHEAT

B. Salim, Salloom; S. Kudayr, Lurna

	DETERMINATION OF WATER TABLE CONTR IBUTION TO ACTUAL VAPOTRANSPIRATION FOR BREAD WHEAT
The Iraqi Journal of Agricultural Science
Article 1, Volume 42, Issue 0, 2011, Pages 126-137
Authors
Salloom B. Salim; Lurna S. Kudayr
Abstract
To determine the contribution from a shallow water table to the evapotranspiration process over the growing season or wheat under different depletion rates and Irrigation depth, a field study was carried out during 2008/2009 at the field of the College of Agriculture Baghdad. Three levels of depletion rates %50, %70, and %90 from available moisture and three Irrigation depths of the effective root zone, 0-30 cm from planting to the end of growing season, 0-30 cm from planting to flowering stage then 0-60 cm from flowering stage to the end of growing season and 0-60 cm from planting to the end of growing season. Amount of Irrigation water was applied to satisfy water depletion in soil over the grawing season. 'Water content deficit was determined by gravimetric method. Calculated water content deficit was based on measurements of soil water content by gravimetric method. Contribution from the water table during each Irrigation was calculated from changes in water content and hydraulic head measured before and after Irrigation for each layer between the end or root zone and the water table. Flux calculation was based on Richard equation and similar to Salim(2003) approach. It was found that at %50 depletion rate from available moisture water table contributed 78, 69, 25 mm during growing season which consitituted %17.6 , %14.5 , %4.7 from the total evapotranspiration for the 0-30 cm, 0-30 then 0-60 cm and 0-60 em irrigation depths, respectively. At (%70 depletion from available moisture water table contributed 87, 74, 33 mrn which consitituted %J20.0, % 15.8, %6.4 from total evapotranspiration for 0-30 cm, 0-30 then 0-60 cm and 0-60 cmirrigation depths, respectively. At %90 depletion (rom the available moisture water table contribution 93,79, 37 mm which consititutcd %20.8, %17.0, %7.2 of the total evapotranspiration for 0-30 cm, 0-30 then 0-60 cm and 0-60 cm irrigation depths, respectively. Results of this study showed that contribution of the water table increased with increased depletion rate of the available water in the root zone. Higher contribution from the water table occurred under 0-30 cm irrigation compared with 0-30 cm, 0-30 then 0-60 cm and 0-60 cm irrigation depths. Lower matric suction values were obtained at 0-30 cm due to evaporation and transpiration process resulting in higher gradient values.

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