Nate Bruce, Farm Business Management Specialist, nsbruce@udel.edu. Drew Harris, Kent County Ag Agent, raharris@udel.edu
Last year, producers across the Delmarva region experienced record wheat yields. Despite the unprecedented yields, an exceptionally wet harvest season last year brought attention to poor falling numbers and their impact on potential revenue. Despite high yields and decent prices, many producers in the region received either price dockages or load rejections at the elevator due to falling number test issues. Falling number issues typically come with test weight, and vomitoxin issues. With the wheat harvest coming up across the region, this article will discuss falling numbers and strategies to minimize low falling numbers in wheat.
A falling number test measures the amount of pre-harvest sprouting that occurs in grain while still on the stalk in the field. The test is used to determine the enzymatic activity in the grain, specifically alpha amylase. For wheat, falling number can give insight into the baking and milling quality of the product. A falling number test creates a slurry of flour and water in a test tube. The measure for the test is how many seconds a plunger falls to the bottom of the test tube that contains the slurry. A high falling number means the plunger took longer to fall through the slurry than a low falling number. High falling number results mean there is low enzymatic activity in the wheat, and it has not begun to germinate. A low falling number indicates the grain has begun to germinate and the enzymatic activity is high, hence the wheat is low quality for milling and baking purposes. Falling numbers over 250 are most desired for baking purposes with most large-scale commercial bakeries working in an ideal falling number range between 250 and 300. A falling number test below 250 is often subject to elevator dockages and wheat loads with a falling number test below 230 can be outright rejected. Even a minimal percentage of wheat kernels with a low falling number test on a load can negatively impact the entire delivery. Below is an image that shows baking results using wheat with different falling numbers.
Environmental conditions are the primary culprit of low falling number test results. Weathering cycles that include wetting and drying periods, alter the overall makeup of the kernels. The fluctuations in moisture levels cause swelling and contraction of the seed. As the kernel absorbs more water, pre-harvest sprouting occurs. This is not ideal because pre-harvest sprouting likely means that carbohydrates and proteins within the kernel have either been transformed or diminished. Not only is the falling number impacted in these circumstances, but also the test weight since alterations from environmental factors have changed the density of the seed. The standard test weight for wheat is 60 lbs. per bushel and on average wheat grown on Delmarva has a test weight that ranges from the mid 50 lbs. per bushel to the low 60 lbs. per bushel. Lower test weights in the mid to low 50 lbs. per bushel are substandard and can result in dockage. One of the most effective ways to minimize pre-harvest sprouting is to harvest at the proper time. It is recommended to harvest and dry wheat the first time it reaches 20% moisture content or the first time it reaches 15% moisture if drying is not possible. Overall time is precious when it comes to harvesting wheat. To avoid potential dockage or rejection situations from a low falling number, prompt harvesting at key moisture levels is essential. Another way to reduce poor falling number test results is to choose cultivars that have good pre-harvest sprouting resistance. Similar to cultivar selection for disease resistance or test weight, pre-harvest sprouting can be dependent upon genetics. Additionally, pre-harvest sprouting can be minimized by avoiding the creation of swaths during harvest.It is best to straight harvest a wheat crop.