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Understanding Falling Numbers in Wheat

It’s always useful for farmers to have an idea of the quality of the grain in their bins to help them determine what protein level or grade their crop is likely to meet. There are many different factors which affect grain quality and many different ways to test for them. One quality assessment tool that is much more prevalent in the U.S. than in Canada is the falling numbers (FN) test, which is used to estimate the amount of sprout damage in wheat, barley or rye.

“A lot of producers may have heard from U.S. sources that if you have high FN you have high quality wheat and you will get top dollar and that is simply not true,” says Daryl Beswitherick, program manager of quality assurance standards and rein-spection with the Canadian Grain Commission (CGC).

“Sprout damage and FN is only one aspect of grain quality, it is not the sole aspect,” says Dr. Dave Hatcher, a research scientist at the Grain Research Laboratory in Winnipeg. “Many producers believe that the whole system could be revised simply around changing to FN and that is a very erroneous idea. FN only deals with sprout damage — there is so much more that goes into grading than that.”

The FN test measures the amount of alpha-amylase, an enzyme important in germination, which is present in the grain. Alpha-amylase converts starch in the grain kernel into energy for the growth stage of the plant, so the more alpha-amylase that is present the greater becomes the potential for sprouting of the grain. The measurement is expressed as the time in seconds it takes for a plunger to fall through a heated slurry of ground grain. The plunger falls more quickly as more alpha-amylase is present. The faster it falls the lower the number, so a higher falling number means there is less sprout damage.

The FN test is not commonly performed in Canada, and certainly not at the delivery point. “The FN test is a laboratory-oriented process and with current technology it takes too long to do in a driveway situation at the elevator,” says Bestwitherick. “What we do in the grading situation is visually count sprouted kernels and use this to predict what the FN should be.”

The drawback of the visual test is that it may not detect germinating kernels that do not show symptoms of sprouting. “There may be circumstances where the kernel seems sound and you won’t see a sprouted kernel, but processes are already occurring within it that can lead to low FN,” says Pam deRocquigny, cereals specialist with Manitoba, Agriculture, Food and Rural Initiatives. “I equate it to FDK (fusarium damaged kernels) and DON (Deoxynivalenol, a mycotoxin produced by fusarium species). DON is what the markets are concerned about in terms of what’s in the grain, but we use a visual FDK test as a grading standard to try and predict what level of DON there is in the grain.”

The meaning of FN

Falling Number is particularly important in milling wheat. Minimum requirements for FN are largely determined by industry, where consistency is a primary concern, and is the reason why most wheat shipments must achieve a FN of 300 sec or higher. Most Canadian wheat varieties generally have a FN of 350 to 500 sec.

Bakers need a certain amount of alpha-amylase in their flour to break down the starch into sugars which feeds the yeast, allows fermentation to occur and makes their product rise. Making sure just the right amount of this enzyme is present starts with the FN.

“Millers routinely order 30,000 to 35,000 tons of wheat at a time and the flour they produce from that wheat must be consistent,” says Hatcher. “The key point is that you can add alpha-amylase to good quality flour but you cannot take it out. So what the industry wants is wheat that has a FN which guarantees a low amount of alpha-amylase enzyme is present. They can then mill it into flour and achieve a consistent product that can be tweaked to meet the specific requirements of their customers.”

As the grain marketing industry is changing across Western Canada, some believe that FN may become a more important test in the future. “It’s a matter of economics,” says Hatcher. “With the change in the structure of the Canadian Wheat Board, grain companies will likely be carving out their own niches in the marketplace, more so than they are at the present time, and in doing so they will each be trying to secure customers with specific quality criteria, one of which will be FN.”

Where the FN test is regularly performed is by plant breeders and cereal chemists during evaluations of potential new varieties for registration.

“We do special dormancy tests whereby we grow plots from which we harvest materials and treat them in a rain simulator,” says Gavin Humphreys, a wheat breeder at AAFC’s Cereal Research Centre in Winnipeg. “Once the material has been weathered artificially under controlled conditions we do FN testing which allows us to determine the range of sprouting resistance of the material under evaluation.”

Since 1999 a falling number working group led by the CGC with participation from the CWB, producer groups and grain companies has been working to try and develop a simpler, more functional FN test. “One of the key problems is trying to make certain that whatever methodology we come up with is functional in a primary elevator and reproducible across the country,” says Hatcher. “We are trying to make sure we have a FN test that is fair and representative so that the producer and the grain companies are getting true value for their grain.”

The working group has evaluated a number of different technologies, but have yet to find one which meets the requirements of the CGC and the industry. A product which showed great promise and which could have been used at the farm level to determine FN was, disappointingly, removed from the market by the proprietary owner of the technology.

“A product like that one had many benefits for the farmer, who could have used it to determine the FN of his grain right in his own machine shed,” says Hatcher. “I can see as the size of farms increases that many farms will want to pursue this type of testing so that they can market their grain effectively, because with removal of the CWB single desk, it’s going to be an open market place for the farmer and he may want to hold his grain and play the market, which means he will need to know the full quality potential of that grain.”

Managing for pre-harvest sprouting

Weather conditions play a huge role in pre-harvest sprouting of wheat and other cereals. Periods of cooler, wet weather at the stage when the crop is mature and starting to dry down, followed by warm, dryer weather are ideal for sprouting to occur, as the seed will begin to germinate. These conditions are often prevalent in the fall, especially in Manitoba, and sprouting problems can be exacerbated if rain or heavy dew occurs after swathing.

Farmers, especially in areas at higher risk, should consider growing varieties with a higher resistance to pre-harvest sprouting, such as AC Domain, Harvest or McKenzie. In shorter season growing areas farmers may still want to grow early-maturing varieties that offer higher yield potential but have a lower sprouting resistance, such as Roblin or Intrepid, and in these circumstances need to consider making the crop a harvest priority.

“Timely harvesting is not always possible, but especially if you are growing an early maturing variety, with lower pre-harvest sprouting resistance, you need to move it up the chain and get it combined, because you are setting yourself up for problems if you don’t get it harvested in a timely fashion,” says Gavin Humphreys.

Saskatchewan’s Ministry of Agriculture is including pre-harvest sprouting resistance ratings in its 2012 Varieties of Grain Crops listing, which can be found at www.agriculture.gov.sk.ca/Varieties_Grain_Crops.

In-field dry down products can also be used to try and encourage more even maturity, and straight combining of short, strong straw varieties, if practical, is another strategy farmers may consider, says Humphreys.

Storage is another issue that may become increasingly important to Western Canadian farmers as they enter a voluntary marketing system. The ability to store grain longer to try and take advantage of better pricing as stocks are depleted later in the year, means careful consideration of issues like sprouting definitely have to be part of the equation.

“If the storage location is not properly ventilated, and the crop has been taken off early so the moisture content is a bit high, and they don’t have proper drying facilities, they could set themselves up for not only sprouting but spoilage,” says Humphreys. “Having robust storage facilities where they can ensure the crop is not only dried when it comes off the field, but maintain those conditions during storage is essential.” †

About the author

Contributor

Angela Lovell is a freelance writer based in Manitou, Manitoba. Visit her website at http://alovell.ca or follow her on Twitter @angelalovell10.

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