In formulating conclusions for this study it is emphasized that, in some instances, only tendencies are indicated and that further investigation on certain phases of the problem is necessary to make definite statements of facts. This study, however, warrants the following conclusions: 1. For conditions similar to those at Blacksburg, Virginia, the results of this study indicate that maximum yields of corn are obtained when the available moisture percentage is maintained by irrigation at some value between 25 percent and zero. 2 . The amount and distribution of rainfall at Blacksburg, Virginia in 1950 were such that irrigation was not profitable and even detrimental. Decreased yields of corn under irrigation showed that water was not a limiting factor in corn production and indicated a lack of oxygen for root respiration. 3. The rate of depletion of soil moisture was greater for alfalfa than for corn, wheat or burley tobacco; therefore the peak use frequency was less for alfalfa than for the other crops. 4. Burley tobacco appeared to be more sensitive to excess water than either wheat or alfalfa. / Master of Science