Variation in Effectiveness of Supplemental Irrigation on Sweet Corn Yield Components

Supplemental irrigation is of increasing importance in the production of processing sweet corn (Zea mays L.) in the humid Midwest. However, wide variation exists for efficiency of irrigation as related to uniformity and quality as well as yield of this crop. The present study was planned to measure the response of major sweet corn yield components to, and their interaction with, irrigation level as related to genotype, plant competition, and season and to provide guidelines for optimum production practice. Six hybrids were grown at three populations (39,000, 49,000, and 59,000 plants/ha) under low and high irrigation levels on droughty sand in central Wisconsin over a 9-year period. Measurements were made of snapped weight, weight and number of usable husked ears, and percent of usuable ears expressed on a weight and number basis. There were wide yearly differences between irrigation levels for all yield components. Increase in production at high irrigation was greatest for snapped corn weight (34.3%), intermediate for usable corn weight (29.4%), and lowest for usable ear number (13.5%). The additional water provided by high irrigation increased snapped weight at an average rate of .52 metric tons/ha per centimeter of applied moisture and increased usable weight by .28 metric tons; the greatest effect was in dry seasons, the least in cool seasons. Record yields were achieved under high irrigation when August temperature was highest. Moisture during the period from 2 weeks prior to silking until harvest and from silking to harvest was significantly associated with yield. Under high irrigation snapped weight ranked first at the intermediate population while usable ear weight and number ranked first at the high population. Under low irrigation snapped and usable ear weight but not usable number decreased with population. Percent usable ears, by weight and number, was highest at the low irrigation with marked hybrid and population differences. The low population at high irrigation increased prolificacy, while the high population at low irrigation increased barrenness. Hybrid-production practice combinations yielding most also had low coefficients of variability over years. Although high irrigation always increased production, the variation in degree of yield component response emphasizes that efficient production requires coordination of irrigation levels with population, genotype, and season.