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ARS Home » Pacific West Area » Pendleton, Oregon » Columbia Plateau Conservation Research Center » Research » Publications at this Location » Publication #182475
Title: GRAIN PROTEIN AS A POST-HARVEST INDEX OF NITROGEN STATUS FOR WINTER WHEAT IN THE NORTHERN GREAT PLAINS

Author
item ENGEL, R. - MONTANA STATE UNIVERSITY
item Long, Daniel
item CARLSON, G. - MONTANA STATE UNIVERSITY

Submitted to: Canadian Journal of Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/3/2006
Publication Date: 4/1/2006
Citation: Engel, R.E., Long, D.S., Carlson, G.R. 2006. Grain protein as a post-harvest index of nitrogen status for winter wheat in the northern Great Plains. Canadian Journal of Crop Science 86(2):425-431.

Interpretive Summary: The critical protein level in wheat is defined as the percentage below which nitrogen (N) fertility is likely to be deficient for yield. This approach has been used to indicate the N fertility status of spring wheat (Triticum aestivium L.) in the Northern Great Plains. The objectives of this study were to evaluate this concept for winter wheat in this region, and to estimate the added N requirements necessary to achieve maximum yield where winter wheat grain protein concentrations fall below the critical level. A two-year field study consisting of three water regimes, four cultivars, and five fertilizer N levels was conducted near Havre, MT, USA. A consistent relationship between relative yield and grain protein was found, and a critical grain protein concentration of 12.5% was identified. Protein concentrations <12.5% were associated with yield or economic losses from N deficiency, while protein concentrations >12.5% were associated with N sufficiency. This critical concentration was consistent across a wide range of rainfall environments and four winter wheat cultivars. Under conditions of moderate N deficiency, grain protein concentration could be used to predict the amount of additional N, which would have been needed to achieve maximum yields. This can be computed from the difference between the critical level and actual protein concentration (expressed in %), times an N equivalent that varies from 25 to 43 lb of N per acre depending on amount of plant available moisture.

Technical Abstract: The use of grain protein as a post-harvest index of N fertility status has been promoted for spring wheat (Triticum aestivium L.) in the Northern Great Plains, through the establishment of critical grain levels for segregating wheat into N deficient vs. N sufficient classes. The objectives of this study were: 1) to evaluate this concept for winter wheat in this region, and 2) to estimate the added N requirements necessary to achieve maximum yield where winter wheat grain protein concentrations fall below the critical level point. A two-year field study consisting of three water regimes, four cultivars, and five fertilizer N levels was conducted near Havre, MT, USA. A consistent relationship between relative yield and grain protein was found, and a critical grain protein concentration of 125 mg g^-1 was defined using Cate-Nelson R^2 statistics. Protein concentrations < the critical level were associated with yield or economic losses from N deficiency, while protein concentrations > the critical level were associated with N sufficiency. This critical concentration was consistent across a wide range of precipitation environments and four winter wheat cultivars. Under conditions of moderate N deficiency, grain protein concentration could be used to predict the amount of additional N, which would have been needed to achieve maximum yields. This can be accomplished by first calculating the difference between the critical level and actual protein concentration. This difference expressed in % protein, is then multiplied by an N equivalent that varies from 2.2 to 3.8 kg ha^-1 N according to the precipitation environment.