Is it necessary to manage falling number in the field?

Authors: Delwiche, Stephen - Steve; TAO, HAIYING - Washington State University; BRESLAUER, RACHEL - Washington State University; Vinyard, Bryan; Rausch, Steven - Steve

Submitted to: Agrosystems, Geosciences & Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/9/2019
Publication Date: 2/13/2020
Citation: Delwiche, S.R., Tao, H., Breslauer, R., Vinyard, B.T., Rausch, S.R. 2020. Is it necessary to manage falling number in the field? Agrosystems, Geosciences & Environment. https://doi.org/10.1002/agg2.20014.
DOI: https://doi.org/10.1002/agg2.20014

Interpretive Summary: Wheat end-product quality, along with other measurements, is assessed by a procedure known as 'falling number' (FN). FN characterizes the viscosity of a meal-water mixture, which is primarily governed by alpha-amylase, the enzyme that breaks down starch. Generally, the higher the enzyme activity (which translates to low FN), the poorer will be the quality of breads, crackers, cookies, and noodles produced from such wheats. Two weather conditions may lead to low FN: pre-harvest sprouting (PHS) caused by rain and coolness before harvest; and late maturity amylase (LMA) caused by large fluctuations in temperature during grain development. These conditions occur frequently in the hilly wheat growing region of the U.S. Pacific Northwest. In six large commercial eastern Washington-northern Idaho wheat fields over two seasons, a study examined how FN varies within a field, as affected by land elevation, slope, and aspect (directional exposure). The results indicated that in seasons of normal weather, FN is not so greatly varying within a field to consider segregating grain from bad pockets to avoid price penalties at market. This information is of benefit to the grower.

Technical Abstract: Wheat growing areas of the U.S. Pacific Northwest, particularly eastern Washington and northern Idaho, are hillier than other wheat producing areas in the country. This may produce microclimate variation within a field due to differences in elevation and solar exposure. While such variation will cause a likewise variation in yield at harvest, it is unknown whether falling number (FN), an indirect indicator of endogenous a-amylase and hence end-product quality, is also affected. The aim of this study was to determine the utility of using local (sub-field) topographical data to make decisions on segregating potentially low FN wheat from susceptible regions within a field. In two consecutive seasons, six large fields in commercial production were studied to reveal possible effects of elevation and solar exposure on FN. Between 17 and 21 geospatially referenced sites from each field were selected based on prior satellite imagery representing the greatest diversity in topography within the respective field. Elevation, slope, and aspect were determined through referencing land coordinates to USGS elevation datasets and ArcMap tools. Theoretical direct solar radiation flux energy increments were summed over the growing period. Findings indicate that for five of the six fields that an elevation effect on FN was not significant despite a variation as much as 50 m within a field. Direct energy flux was positively correlated with FN for two fields (r = 0.48 to 0.69) in the first season, but negatively correlated for one field in the second season (r = -0.51). However, even in cases when energy flux or elevation trends were significant, these effects were minor. Therefore, we conclude that in circumstances of favorable weather conditions, in-field segregation of wheat during combining is not necessary.