Dryland corn ( Zea mays L.) production increased more than 10-fold from 1995 through 2000 in semiarid western Nebraska. Corn population and N fertilizer management recommendations are needed for this area. The objectives of this study were to determine the influence of plant population and N fertility on corn yields in semiarid western Nebraska. In 1999 and 2000, experiments were conducted each year at four sites. Factorial experimental treatments were five plant populations (17 300, 27 200, 37 100, 46 900, and 56 800 plants ha -1) and five N fertilizer rates (0, 34, 67, 101, and 134 kg N ha -1) arranged in a randomized complete block with five blocks. Corn yields ranged from less than 100 kg ha -1 to more than 5550 kg ha -1. Overall, grain yield increased 353 kg ha -1 with increasing population from 17 300 to 27 200 plants ha -1. Population increases above 27 200 plants ha -1 resulted in inconsistent yield results. Nitrogen fertilization and plant population effects did not interact. Yields were maximized by 202 kg N ha -1 in the form of soil NO 3-N and fertilizer N available before crop emergence. Growers are advised to use a plant population of 27 200 plants ha -1. Economic optimal fertilizer rate can be estimated using the equation: Nfert.=(10.6 * Pcorn- Pfert.)/(0.0526 * Pcorn)- Nsoil, where Pcorn and Pfert. are corn and fertilizer price ($ kg -1), respectively, Nsoil is soil test NO 3-N (kg ha -1) as determined by preplant soil test in a 0- to 120-cm soil sample, and Nfert. is economic optimal fertilizer rate (kg ha -1).
