NITROGEN MANAGEMENT Economically Optimal Nitrogen Fertilization for Yield and Protein in Hard Red Spring Wheat

all current dryland fallow would reduce concentrations of suspended dust particles 10 m and smaller, by up to This analysis determines profit-maximizing N fertilization levels of 95% during extreme wind events, in east-central Washhard red spring wheat (HRSW) (Triticum aestivum L.) for various wheat prices, N prices, and protein-based HRSW price premium/ ington. Annual cropping leaves more surface residue discount (P/D) structures for southeastern Washington data. Fertilizer and/or roughness that protects against wind erosion. response data consisting of rates of N fertilization (kg ha 1), grain Shorter periods between crops also reduce the time peyield (kg ha 1), and grain protein (g kg 1) were used to statistically riod that the soil is unprotected from wind erosion (Paestimate regression relationships that predicted yield and protein in pendick, 1998). However, Young et al. (2001) report response to N. Experiments were located near Pullman, WA (550 mm that continuous no-till (NT) HRSW in this region has average annual precipitation). All predicted net return maximizing been less profitable than wheat–fallow rotations based N, protein, and yield levels were within the data range. Increasing on standard fertilization practices. If annual production P/D incentives for protein increased optimal N, the expected economic of HRSW with optimal N fertilization can be shown to result. At the high P/D structures, the P/D structure dominated N and wheat prices in determining optimal N application levels. Overall, be profitable, both economic and environmental objecnet return–maximizing yields varied only modestly with changes in tives could be served. both N and wheat price in this data set. However, in all scenarios, as The price that a producer receives for HRSW, unlike P/D incentives increased, net return–maximizing N levels were beyond soft white wheat, is influenced by protein concentration the level that resulted in maximum yield. At the two lowest P/D (g kg 1). Premiums ($ Mg 1) are added to the base wheat structures, which provided the lowest reward for protein, it was most price (reported at 140 g kg 1 protein) for each 2.5 g profitable to fertilize for slightly less than 140 g kg 1 expected protein. kg 1 above 140 g kg 1 protein and discounts ($ Mg 1) These results indicate that it is not always profitable to use 14% subtracted from the base price for each 2.5 g kg 1 below protein as an N fertilization goal. 140 g kg 1 protein. Historically, discounts have been weighted more heavily than premiums. Table 1 reports regional yearly average price and corresponding P/D P of HRSW by dryland farmers in the Pastructure for 1991–1992 through 2000–2001 (USDA, uncific Northwest has increased in recent years, possipublished, 2001). Note that premiums vary greatly from bly due to low prices for soft white wheat relative to $0.37 Mg 1 to $4.78 Mg 1 and discounts from $1.10 Mg 1 production costs. Hard red spring wheat has maintained to $8.54 Mg 1 over this 10-yr period. a varying price advantage over soft white wheat in recent Since both yield and protein affect profit, economiyears (Janosky, 1999; USDA, unpublished, 2001). Varically motivated growers will desire to apply N fertilizer ety trials near Pullman, WA, from 1997 to 2001 show to HRSW at rates that maximize profit considering both that HRSW yield has averaged 202 kg ha 1 less than yield and protein. The grower controls some factors soft white spring wheat (Burns et al., 2001). However, affecting yield and protein: N application rate, seeding recent trends with newer varieties show HRSW yields rate, and variety. Moisture available to the dryland crop gaining on soft white spring wheat. is a very important uncontrollable factor that deterProfitable fertilization and other management pracmines protein content. While preplant soil moisture and tices of continuous HRSW also promote environmental preplant soil NO3 are measurable, growing season preobjectives. Annual cropping of HRSW as a substitute cipitation is beyond the dryland grower’s control. for traditional winter wheat–summer fallow in lowerVaughan et al. (1990) found that a quadratic relationrainfall cropping regions can reduce wind erosion and ship existed between hard red winter wheat yield and air pollution in the semiarid Pacific Northwest. Lee both falland spring-applied N in eastern Colorado. A (1998) estimated that annual spring grain cropping of quadratic relationship was found between protein and fall-applied N and a linear relationship between protein D.A. Baker and D.L. Young, Dep. of Agric. and Resour. Econ., Washand spring-applied N. This Colorado research showed ington State Univ., Pullman, WA 99164-6210; D.R. Huggins, USDAgrain yield response to N fertilization depended on preARS, Pullman, WA 99164; and W.L. Pan, Dep. of Crop and Soil Sci., Washington State Univ., Pullman, WA 99164-6420. Funding was cipitation and residual soil NO3 while grain protein reprovided by the College of Agriculture Research Center, Washington sponded to N fertilization regardless of precipitation and State University, Pullman, WA 99164-6210. Received 23 Sept. 2002. soil NO3 levels. High levels of soil NO3 and low moisture *Corresponding author ([email protected]). Published in Agron. J. 96:116–123 (2004).  American Society of Agronomy Abbreviations: CT, conventional tillage; HRSW, hard red spring wheat; NT, no-tillage; P/D, premium/discount. 677 S. Segoe Rd., Madison, WI 53711 USA