Problems with Low Falling Numbers in the 2018 Crop

The 2017 crop brought a much-appreciated relief from the low falling numbers problems of 2016. Unfortunately, some farmers are experiencing problems with low falling numbers in the 2018 crop.

The Hagberg-Perten falling number machine measures starch digestion based on the thickness of a gravy made from whole-grain flour and water. The falling number test measures how long it takes a stirrer to fall through the gravy in seconds. Higher alpha-amylase causes the stirrer to fall faster through thinner gravy, resulting in a low falling number. Alpha-amylase enzyme in the wheat grain results in lower falling numbers (thinner gravy) because the enzyme digests starch, reducing its gelling capacity. Wheat grain is discounted for low falling numbers, because our overseas customers have found that falling numbers below 300 seconds are associated with a high risk of poor end-use quality, such as cakes that fall, sticky noodles, and poor texture of baked goods.

Low FN and elevated alpha-amylase can result from weather events, such as preharvest sprouting and LMA (late maturity alpha-amylase). Preharvest sprouting is the initiation of germination on the mother plant when rain occurs after grain maturity. LMA is the production of alpha-amylase in response to a cold temperature shock during late grain filling. Susceptible varieties induce LMA if they experience cold shock during the soft dough stage as the maturing grain transitions from green to yellow. Grain in the milk stage should be too young to experience LMA.

I suspect that 2018 falling numbers won’t be quite as low as they were in 2016.  While this may be small consolation for farmers with lower FN, it is good for our reputation with our customers because we will be able to sell higher FN grain this year.

Stages of LMA sprouting from before maturity to after-ripped and not dormant.
Several factors suggest the 2018 low falling numbers problem may be less severe.  First, the temperature fluctuations in 2016 were repeated and more extreme than those in 2018. Second, much of the Washington wheat crop was still in the milk stage during the coldest temperatures in June. Finally, the 2016 wheat crop experienced both LMA and preharvest sprouting due to rain. This year, most of the winter wheat crop has been harvested and the spring wheat crop is maturing rapidly with little rain in the forecast.
While harvesting in a timely fashion after maturity can reduce your risk of preharvest sprouting, it cannot prevent LMA. Moreover, farmers must be careful not to harvest green wheat. Green kernels tend to cause lower FN due to the presence of alpha-amylase produced during early grain development.

LMA is notoriously inconsistent. Whether or not a particular farm sees low falling numbers due to LMA this year will depend on how far along their wheat crop was in grain filling when the cold temperatures hit. Given the timing of the cold temperatures, LMA susceptible varieties that flowered earlier may be more likely to have low FN. Thus far, we’ve seen some low FN below 250 in susceptible varieties in variety trials from Dusty, Dayton, Horse Heaven Ritzville and Walla Walla. Falling numbers below 300 have also been discovered from the trials in Anatone, Connell, Eureka, Harrington, Lind, and Pullman but these have been between 250 and 300.

The only way we can prevent LMA is by growing cultivars with more genetic resistance. To help farmers choose resistant varieties, we will post falling numbers data from the Washington State Cereal variety trials on the PNW falling numbers website. USDA-ARS and Washington State University scientists have also undertaken a massive LMA testing project to select resistant new cultivars.

Further information can be found on the Grain Quality Resources webpage from Wheat and Small Grains website.


For questions or comments, contact Camille Steber via email at camille.steber@ars.usda.gov or contact Kim Garland-Campbell via email at kim.garland-campbell@ars.usda.gov.

Washington State University