Irrigation and evaporative cooling of ‘Red Delicious’ apple trees over 2 growing seasons resulted in a reduction in environmental stress as evidenced by plant and air temp reductions (8). The trees were spot-picked weekly, based on acceptable color to meet grade standards. Harvesting was completed one week earlier on trees receiving overtree sprinkler irrigation as compared to those with undertree or no irrigation. Fruit from trees which received overtree irrigation had greater surface coloration and nearly twice as much surface area with good solid red color as fruit which received undertree or no irrigation. Overtree irrigation improved fruit size and shape during 1969 but not 1970; increased soluble solids, and reduced cork spot and bitter pit in 1970. Lower firmness of overtree irrigated apples in 1969 was attributed to their greater size. Irrigation (over and undertree) had no influence upon internal breakdown measured after 4 months of storage at 32°F.
Received for publication June 9, 1971. Paper No. 3486 of the Journal Series of the North Carolina State University Agricultural Experiment Station, Raleigh.
Assistant Professor of Horticultural Science. The author wishes to acknowledge the assistance of R. N. Sneed, Department of Biological and Agricultural Engineering, E. Lutz & Son, Cleveland County, North Carolina, grower-cooperator; and M. G. Robertson, Research Assistant, Department of Horticultural Science.