CORN PRODUCTION IN RELATION TO WATER INPUTS AND HEAT UNITS

Increasing areas available for corn (Zea mays L.) production in eastern Canada have stimulated the search for improved management practices to obtain higher yields. These management practices include hybrid selection, plant density, and fertility optimization. Large year-to-year variations in corn yields due to weather, however may mask management effects. The objective of this study was to quantify corn grain yield, stover yield, and total dry-matter production as functions of heat units (HU) and total seasonal water inputs. A field experiment was conducted on a Brookston sandy clay loam soil (fine-loamy, frigid, mesic Typic Hapludalf) in Quebec from 1984 to 1989. Empirical equations for corn grain, stover, and total dry-matter yield were developed for combinations of two plant populations (65 000 and 90 000 plants ha-1) and two fertilizer rates (170-44-141 and 400-132-332 kg ha-1 as N-P-K). Corn grain yield was a function of HU under conventional management practices with low and high HU reducing yields. Corn grain yield with the higher plant population and the higher fertilizer rate was proportional to the product of HU and water inputs received during the growing season. Interactions between management practices indicated that management practices must be devised for most probable climatic conditions. Optimization of climatic factors and management practices could increase grain corn yield.