Abstract
ABSTRACT
The daily rainfall (amount and distribution) for 28 years at Mosul area along the growing season of wheat crop are studied . The objective is to determine the onset rainfall for rainfed cropping of wheat..
Two computer simulation models were formulated, tested and then used in the study. The first model was to estimate the onset rainfall (date). The output of this model for all years is used as an input for a second simulation model that monitors the daily water budget in the entire root zone depth of a growing season of a wheat crop in order to estimate the evapotranspiration and variation of water content in the soil profile over the season along with the date and amount of one , two , or three supplemental irrigations during the season. The goal of these irrigations is to convert certain failure years to successful year for rainfed cropped wheat.
The study showed that adding one supplemental irrigation (75 mm) around the end of the rainy season increased the yield ratio by 9% while applying two supplemental irrigations has increased the yield ratio by 30% and converted four failure years to successful ones. It is also shown that the return from supplemental irrigation is economically feasible in all of the studied cases .
