Managing Nitrogen and Sulfur Fertilization for Improved Bread Wheat Quality in Humid Environments W. E. Thomason, 12 S. B. Phillips,' T. H. Pridgen, 1 J. C. Kenner,' C. A. Griffey,' B. R. Beahm, 1 and B. W. Seabourn4 ABSTRACT Cereal Chem. 84(5):450-462 A large proportion of the wheat (Triticu,n aeslivum L.) milled and utilized by bakeries in the eastern United States is hard red winter wheat (HRWW). Potential for producing this higher value commodity in the eastern United States is dependent on availability of adapted HRWW cultivars that are competitive with soft red winter wheat (SRWW) culti- vars and implementation of management systems to enhance end-use quality. The effects of late-season nitrogen (N) (0-45 kg of N/ha) applied at two growth stages (GS 45 and 54) and sulfur (5) (0-34 kg of S/ha) applied at GS 30 on grain, flour, and milling and breadbaking quality were evaluated. Three diverse wheat cultivars (Soissons. Heyne. and Ren- The wheat milling capacity in the Mid-Atlantic region of the United States is 2,900,000 Mg of grain/year (World Grain Inter- national 2006). A large portion of this grain is purchased by region- al mills from other wheat growing areas, especially the Great Plains of North America. Some millers use only hard wheat, which is almost exclusively grown outside the Mid-Atlantic region (C. J. Lin, personal communication). Hard wheat and certain strong gluten soft wheat cultivars are suitable for use in making bread products. Because general market values for these types of bread are higher for hard wheat than soft wheat ($14.68/Mg or more), producers are interested in using adapted cultivars and developing agronomic techniques to grow bread wheat in the humid, high-rain- fall environment of the Mid-Atlantic region. Millers in the Mid- Atlantic region are interested in obtaining locally grown bread wheat because transportation costs, and thus total cost, would he greatly reduced for grain produced in the region. Efforts in the Mid-Atlantic region to identify and breed adapted bread wheat lines have shown promise in comparison to traditional HRWW cultivars, which do not yield as well as adapted SRWW cultivars. Data from the Virginia Elite and Uniform Bread Wheat Trials indi- cate that current soft wheat cultivars out-yield HRWW cultivars by 0.8 to 1.3 Mg/ha. Because N availability is frequently the main determinant of grain yield and protein concentration in wheat, sufficient N should be applied so as not to limit either grain yield or quality (Olson et al 1976; Grant et all 1985). In fact, grain protein concentration has been shown to increase at N rates above those necessary to sup- port maximum yields (Kelley 1993). However, excessive plant- available N produces wheat plants more prone to lodging and disease development with subsequent reductions in yield and increased input costs (Crook and Ennos 1995). The potential for elevated nitrate levels in ground and surface waters also increases with excessive N fertilizer applications (Coale et al 2001). Late- season N applications to wheat have increased nitrogen use effi- ciency and produced similar yields with less total N by matching N application timing with plant demand (Ellen and Spiertz 1980). However recent work has reported lower apparent fertilizer re- Virginia Polytechnic Institute and State University. Blacksburg VA 2406!. 2 Corresponding author. Phone: 540-231-2988. Fax: 540-231-3075. E-mail address: wihomaso@vi.edu Virginia Crop Improvement Association, Mechanicsville, VA. USDA-ARS Grain Marketing and Production Research Center, Manhattan, KS. doi; 10.1 094/CCHEM-84-5-0450 © 2007 AACC International, Inc. 450 CEREAL CHEMISTRY wood 3260) were studied in two to five environments. Application of S and late-season N had little effect on grain yield. But N consistently increased grain and flour protein as well as bread loaf volume. The magnitude and significance of response to N and S varied by location and cultivar. While S alone did not have a significant effect on grain protein, S availability was critical in obtaining increased grain protein. Breadhaking quality of HRWW cultivars produced in the eastern United States can be improved through implementation of nutrient management approaches that include late-season application of 34-45 kg of N/ha and addition of 5, particularly on sandy soils where S availability in the subsoil is low. covery from the late-season nitrogen application when N supplied earlier in the season was adequate to achieve optimum yields (Gooding et al 2007). Wheat yield and protein concentration are inversely related due to energy constraints and dilution effects within the plant (Pear- man et al 1978: Halloran 1981). Under favorable growing condi- lions, starch and protein increase simultaneously, but under water and temperature stress, the conversion of sucrose to starch may be hindered. Protein formation is much less affected by these condi- tions and protein level is typically greater in wheat grown under stress of water and temperature (Brooks et al 1982; Bhullar and Jenner 1986). Because cultivars of SRWW grown within wet, humid environments are typically lower in grain protein than HRWW produced in drier production areas (Dimmock and Gooding 2002) and because relatively high grain protein levels are needed for bread production, additional breeding and management techniques are both required to increase grain protein concentration with minimal economic and environmental impacts. Increased grain protein concentration resulting from late-season foliar N application has been demonstrated in bread wheat in other regions (Wuest and Cassman 1992; Phillips et al 1999; Woolfolk et al 2002) and has only recently been examined in more humid areas, and then grain protein was the only quality parameter re- ported (Kratochvil et al 2005). Baking quality of wheat flour typically increases with increased grain protein (Randall et al 1990), which is a major indicator of bread wheat quality, especially as related to loaf volume (Stoddard and Marshall 1990). Extremely high-protein concentration can result in decreased breadmaking quality because N is accumulated in grain as gliadins or nonprotein N fractions (Borghi 1999). Rate and timing of N application affect breadmaking quality (Guttieri et al 2005), with late-season application typically increasing grain protein levels (Wuest and Cassman 1992). Increased grain protein concentration does not always result in increased breadmaking quality because of the imbalance in N and S content as protein level increases (Timms et al 1981; Stoddard and Marshall 1990). Limited S availability favors the synthesis of low-S gliadin storage proteins and high molecular weight subunits of glutenin at the expense of S-rich proteins (Wrigley et al 1980). Sulfur deficiency decreases the quantity of polymeric proteins and shifts the distri- bution from polymeric to lower molecular weight proteins (Mac- Ritchie and Gupta 1993). These changes in protein composition are associated with alterations of dough rheology. Research in New Zealand has demonstrated that sulfur fertilizer decreases dough mixing time and work requirements compared with N alone or no