|Reardon, Catherine - Kate|
|ENGEL, RICHARD - Montana State University|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/30/2016
Publication Date: 3/9/2017
Publication URL: http://handle.nal.usda.gov/10113/5934964
Citation: Long, D.S., Reardon, C.L., McCallum, J.D., Engel, R. 2017. Nitrogen requirement to change protein concentration of spring wheat in semiarid Pacific Northwest. Agronomy Journal. 109:675-683.
Interpretive Summary: Wheat growers in the Pacific Northwest are interested in applying information from grain protein and yield maps into precision nitrogen management, but protein-nitrogen relationships for enabling this approach have not been established in this region. A three year study was conducted in eastern Oregon in which six popular cultivars of spring wheat were grown under varying nitrogen and water levels. An application rate of approximately 55 lb of nitrogen per acre was associated with a 1% change in protein content for grain yields that can be realistically expected under low precipitation. With this knowledge, dryland farmers in lower rainfall areas of the region will be able to use yield and protein maps to estimate crop nitrogen removal and vary nitrogen in fields at the rate it was removed by the previous crop and target a desired protein level in the next crop.
Technical Abstract: On-combine yield monitors and grain protein analyzers enable mapping of grain N removal at time of harvest. Nitrogen removal maps combined with estimates of the fertilizer N equivalent (FNE) for each unit (g kg-1) change in grain protein concentration (GPC) are useful for developing site-specific fertilizer prescriptions for fields. This study was conducted to determine the critical protein concentration where yield is maximized and FNE for spring wheat (Triticum aestivum L.) grown under low annual precipitation (<350 mm) in the inland Pacific Northwest. Five hard red spring (HRS) cultivars and one soft white spring (SWS) cultivar were grown under three water levels over an N application range of 0-235 kg ha-1 in eastern Oregon. The critical protein level required to maximize yield was 140 g kg-1 for HRS wheat and 117 g kg-1 for SWS wheat. When water was limiting, GPC increased with added N while yield response was absent indicating GPC may not be useful as a post-harvest indicator of N sufficiency when yields are water limited. The FNE for HRS wheat was 59 kg ha-1 which is three times that reported in northern Montana. For SWS wheat, the FNE was 54 kg ha-1 under low water supply. To achieve acceptable GPC for spring wheat, growers in low rainfall areas of inland PNW should expect to add (or subtract) these amounts of N to change protein by 10 g kg-1.