Proper nitrogen (N) management and variety selection are important for profitable hard red winter (HRW) wheat production in the dryland growing regions of northeastern Oregon. In these dryland systems, N management for grain yield and grain protein concentration (GPC) is challenging due to climatic and year-to-year variation in production environments. However, current fertilizer guides make little distinction between locations and incorporate relatively little data from HRW production. Identifying adequate N management practices and scenarios suitable for HRW production will help producers reduce risk and enhance profits. This study investigates the effects of fertilizer N rate, N application timing, variety and location over six site-years in northeastern Oregon from 2007-2009. Whole plant tissue nitrogen (TN) concentration at Zadoks growth stage (GS) 30 and flag leaf nitrogen (FLN) were also evaluated as decision making tools for N management in this region. Three sites representing low and intermediate precipitation zones were chosen for this study. A site at Pendleton, Oregon represented an intermediate precipitation zone (420 mm), while sites at Lexington and Arlington, Oregon were in a low precipitation (250-300 mm) zone. Study sites were minimally responsive to N treatments in terms of yield. Spring N was less detrimental to yield than fall application when N was excessive at Lexington and Arlington. Grain protein concentration response to fertilizer N was significant and varied by site-year. Some site-years proved favorable for efficient production of high GPC HRW wheat, whereas acceptable GPC was very difficult to achieve in others, underscoring the difficulty of consistently producing high GPC HRW wheat in these regions. Fertilizer N use efficiency was 18-39% at Pendleton, but generally less than 20% at Lexington and Arlington, dropping to zero in some circumstances. At all sites the soil N pool was used more efficiently than fertilizer N, indicating that HRW production is best suited where only minimal fertilizer N is required to complement crop N requirements. Spring N application improved GPC one year at Pendleton following above average late spring rainfall, and may therefore be a useful N management strategy in that environment. In contrast, spring N had a neutral or negative impact on GPC at Lexington and Arlington. Overall, current recommendations did not adequately describe N requirements observed in this study. However, requirements for achieving target GPC were generally lower and more stable at Pendleton, indicating that this and similar environments may be more suitable for HRW production than low yield, high stress environments such as Lexington and Arlington. Varieties showed similar response to N treatments regardless of site. Grain yield of HRW varieties were generally competitive with the soft white winter (SWW) variety 'Stephens'. Among tested HRW varieties, 'Norwest 553' expressed the best combination of yield and GPC performance. The relationship of tissue N (TN) concentration at Zadoks growth stage 30 to GPC was stable across site-years. A critical TN level of 41 g kg-1 corresponded to 126 g kg-1 GPC. This level could be used to indicate when additional N is required to achieve desired GPC, but it remains uncertain how useful this test would be at high stress, low rainfall sites considering the poor response to spring N at Lexington and Arlington. Flag leaf N also showed promise for predicting GPC, but additional research is necessary to clarify this relationship.

The purpose of this study was to evaluate differences between winter wheat varieties in response to nitrogen fertilizer. Seven nitrogen fertilizer rate x variety factorial experiments were conducted in several environments. Dry matter and nitrogen yields at boot, soft dough, and harvest and grain yield components were measured. The yield component data were evaluated in terms of storage capacity which is assumed to be proportional to kernels /rn2 for a given variety. The kernels /m2 was divided into two components, spikes /rn2 and kernels/spike. The spikes /m2 of each variety were closely related to the boot nitrogen yield, but not to boot dry matter yield or plant nitrogen content. Since the kernels/spike generally remained constant or increased as the boot nitrogen yield increased, the kernels/m2 appeared to depend on the boot nitrogen yield. The variety Hyslop had high dry matter and nitrogen yields at boot stage of growth. This appears to allow it to have excellent storage capacity as measured by kernels /m2 . Good growth by boot stage appears to lower the nitrogen fertilizer rate needed for maximum grain yields. The variety Nugaines had relatively low growth and nitrogen uptake by boot. This may be the reason why it needs a higher fertilizer rate than Hyslop to obtain adequate storage capacity (kernels/m2). However; Nugaines had better growth after soft dough stage. At the dryland locations this may be due to slower depletion of the soil water. At the irrigated locations it may be due to greater late tillering. Hyslop and Nugaines differed in the pattern of yield component adjustment to improving environment. Hyslop mainly increased its average kernels/spike rather than spikes/m2 . Nugaines had greater increases in spikes/m2 but smaller increases in kernels/spike. This may be related to their different cuim sizes and tillering. Hyslop forms a few large culms early in the season, but Nugaines continues to tiller during stem elongation. Coulee was intermediate between Hyslop and Nugaines in patterns of growth over time and pattern of yield component adjustment to improving environment. It had good yields at moderate nitrogen rates, and high nitrogen rates did not appear to be needed for adequate storage capacity. Wanser consistently had low grain yields, which was due to low kernels/m2 . Nitrogen fertilizer increased its height more than the shorter varieties and this was associated with reductions in kernels/spike: Thus the height growth of Wanser may compete with its ear development and cause poor storage capacity. Wanser had slightly greater grain nitrogen percentage than other varieties, but this was simply associated with its low grain yield. There were only small varietal differences in the percentage of plant nitrogen translocated to grain. However, environment and nitrogen fertilizer rate greatly affected this. The club wheat Paha yielded well but usually less than some other varieties. It had high dry matter and nitrogen yields, but after soft dough its dry matter yields decreased more than for other varieties. This indicated that it depleted soil moisture earlier than other varieties did. Tx65A1268, a short hard red winter wheat with prolific tillering and small culms, was included in. two experiments. It had the highest grain yield at the low rainfall site. This may be related to its early maturity. However, with irrigation it yielded poorly. This appeared to be due to poor storage capacity since there was no increase in kernels/spike with improving environment. Yamhill, an awnletted wheat, yielded well in the Willamette Valley, but not in eastern Oregon. Estimates of the recovery of fertilizer nitrogen were calculated from the increases in soft dough nitrogen yield caused by each increment of nitrogen fertilizer. At sites with excellent moisture supply the first fertilizer increment was incompletely recovered (44-66%), apparently due to immobilization associated with plant residue decay. With higher fertilizer increments which increased yields, fertilizer recovery values were near 100%. At low rainfall sites under fallow cropping recovery values were 38-56% and decreased with above optimum fertilizer rates. At eastern Oregon sites losses of nitrogen from the plant tops after soft dough ranged from 7-33% depending on variety, location, and fertilizer rate. At maturity the percentage of the total plant top nitrogen in the grain ranged from 60-81%. This percentage decreased with nitrogen fertilization, but was little affected by variety.