Field experiments were conducted in 1996, to evaluate the need of supplemental irrigation of maize on some sandy soils in Eastern Ontario. Field and laboratory measurements of soil properties were conducted. Plow layer and deficit irrigation management approaches were evaluated. Irrigation requirements using rain and evaporation data of the humid 1996 summer, as well as data from the drier 1974 summer, were evaluated. The results show that using a root zone depth less than 300 mm led to more water losses by drainage, more irrigation water requirements and more frequent irrigation applications, as compared to using a 400 mm root zone. Therefore, it is recommended that a 400 mm root zone depth be used for scheduling irrigation applications of 25 mm. Wilting began to appear at 60% soil moisture depletion. Thus, 50% moisture depletion is suggested as the time to start irrigation to avoid crop stress. / The principal assumptions for tabulation of irrigation scheduling were: (1) That the soil is at field capacity at the beginning of June; and (2) That upward flux from a water table is negligible, since the summer water table is deeper than 2 m. These assumptions are based on the facts that rain in May keeps the soil moist, the maize is small at the end of May and that AET (Actual Evapotranspiration) is less than PET (Potential Evapotranspiration). / The measurements show that soil moisture depletion varies from site to site within the fields. The water balance was calculated using weather data and available soil moisture holding capacities for three locations on the farm. The tensions that the plant roots exerted to obtain water from the soil were measured with tensiometers and tabulated as a guide for irrigation management.

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