Interactions of Nitrogen, Weather, Soil, and Irrigation on Corn Yield

but no difference in yields with increased N when the season was cool. Numerous factors that affect corn yield in the Northern Great Soil moisture status is also important in maintaining Plains are not considered in current N fertilizer recommendations. A maximum corn yields, and maintaining optimal soil moislinear model to describe the interactions of N fertility, weather, soil, ture is facilitated by irrigation in areas of coarse-textured and irrigation on corn (Zea mays L.) yield was developed for a 6-yr field study in southeastern North Dakota. Varying rates of postemersoils. Stegman (1982) found that yields decreased with gence fertilizer N were applied to plots in four quadrants of a sprinklerincreased water stress, but if the water stress is limited irrigated field. Four irrigation-scheduling methods varied by year (Y) to one portion of the growing season and irrigation replenand quadrant (Q). Grain yield, stover yield, and N uptake response ishes the profile moisture, high yields can still be achieved. to a covariate (soil N plus starter fertilizer N), N treatment (Nt), Q, Some research has indicated that crop N requirements Y, irrigation treatment (I), previous irrigation treatment (P), and are lower for irrigated versus rainfed soils (Oberle and the two-way interactions that included Nt, were investigated using Keeney, 1990), unless rainfed condition results in water standard regression techniques. Yield increased significantly with Nt stress. up to a rate of 135 kg N ha 1 for most Y, Q, and I. Average yearly Current recommendations for corn fertilization in yield was adversely affected by cool climatic conditions in 2 yr. Soil North Dakota indicate that 21.4 to 26.8 kg of N is needed conditions in two quadrants resulted in a 1.25 Mg ha 1 average annual yield reduction compared with the other quadrants. An irrigation per Mg of corn grain yield, which is equivalent to 1.2 scheduling method utilizing a water balance algorithm resulted in to 1.5 lb of N per standard (56 lb) bushel of corn in higher yields compared with the other scheduling methods. The interconventional units (Dahnke et al., 1992; Berglund and actions of Nt with Q, Y, and I were significant. Optimized total N McWilliams, 1999). Typically, the N recommendations rates (the sum of soil nitrate N, starter N, and postemergence Nt) derived are adjusted for soil test N, date of sampling, and previfrom quadratic-linear plateau analysis varied (232–374 kg N ha 1) with ous crop. Current nutrient recommendations, which are Y, Q, and I and averaged 295 kg N ha 1. Soil properties, soil moisture based on many site-years of yield response curves, make availability, and yearly climatic factors should be considered when no adjustments for variation in weather conditions, soil making fertilizer recommendations. type, and management factors on a site-specific or yearspecific basis (Dahnke and Olson, 1990). The objective of this study was to determine the yield M corn grain yields are influenced by a response of corn in the Northern Great Plains to the number of factors, including N fertility, growing combined effects of increased applied N fertilizer, irrigaseason conditions, water availability, and soil conditions. tion scheduling method, soil type, and yearly climatic Studies investigating N fertility rates have shown that variation. corn yields increase in a quadratic fashion with increased applied N to a plateau level (Cerrato and Blackmer, 1990). Maximum yields have been observed at N rates MATERIALS AND METHODS less than the maximum rates applied in various studies Field Experiments (Onken et al., 1985; Schlegel and Havlin, 1995). Albus and Moraghan (1995) found marked yield responses to For the 1990 through 1995 growing seasons, a field-scale N fertilizer in a number of short-season corn hybrids. study of irrigation and fertilizer N management effects on groundwater quality was conducted near Oakes, ND, USA. In the Northern Great Plains, favorable growing conMeteorological data were measured at an automated weather ditions are important due to the short growing season. station approximately 2.4 km from the site. The weather staDerby et al. (2004) found that yield was adversely aftion was located at 46 04 N, 98 06 W, and 401 m elevation and fected by cool growing season conditions. Similarly, is part of the North Dakota Agricultural Weather Network Swan et al. (1987) reported decreased corn yields with (NDAWN) (Enz et al., 1997). Growing degree units were insufficient cumulative growing degree days (CGDD). calculated from NDAWN data based on a lower limit of 10 C Wienhold et al. (1995) found 60% greater yields with and an upper limit of 30 C (Gilmore and Rogers, 1958). Rainincreasing N fertility when the growing season was warm fall and irrigation amounts were measured directly at the field site. This site was 64 ha, of which 53.4 ha was irrigated by a sprinkler (center pivot) irrigation system. The soil at the site N.E. Derby and F.X.M. Casey, Dep. of Soil Sci., D.D. Steele, Dep. (Fig. 1) was primarily Hecla loamy fine sand (sandy, mixed, of Agric. and Biosyst. Eng., and J. Terpstra, Dep. of Stat., North frigid Oxyaquic Hapludoll) on the south portion of the field Dakota State Univ., Fargo, ND 58105; and R.E. Knighton, USDAand Wyndmere fine sandy loam (coarse-loamy, mixed, superCSREES, Washington, DC 20250. Received 14 Feb. 2005. *Correactive, frigid Aeric Calciaquoll) and Stirum fine sandy loam sponding author ([email protected]). Published in Agron. J. 97:1342–1351 (2005). Nitrogen Management Abbreviations: CGDD, cumulative growing degree days; ET, evapotranspiration; I, irrigation treatment; NE, northeast; Nt, nitrogen treatdoi:10.2134/agronj2005.0051 © American Society of Agronomy ment; Ntot, total nitrogen; NW, northwest; P, previous irrigation treatment; Q, quadrant; SE, southeast; SW, southwest; Y, year. 677 S. Segoe Rd., Madison, WI 53711 USA 1342 Published online August 17, 2005