Is it necessary to manage falling number in the field?

Wheat (Triticum aestivum L.)-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 thus causing corresponding variation in yield at harvest. It is unknown whether falling number (FN), an indirect indicator of endogenous alpha-amylase activity and hence end-product quality, is also affected. The aim of this study was to determine the utility of using local (subfield) topographical data to make decisions on segregating potentially low FN wheat produced from susceptible regions within a field. In two consecutive seasons, six large fields in commercial production were studied to reveal effects of elevation and solar exposure on FN. Elevation, slope, and aspect were determined through referencing land coordinates to U.S. Geological Survey (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 an elevation effect on FN was not significant despite a variation by as much as 50 m within a field. Direct energy flux was positively correlated with FN for two fields (r = .469 and .704) in the first season, but negatively correlated for one field in the second season (r = -.507). However, even in cases when energy flux or elevation trends were significant, these effects were minor. Thus, in-field segregation of wheat during harvest is not necessary in favorable seasons.