HARVEST RAIN CAUSES PAIN
Updated: Sep 18
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July rain is a gift. Harvest rain is a different animal.
Rain on ripe wheat can drop falling number. That's the number bakers care about. When it falls, milling wheat can slide. A number 1 can end up feed.
And here's the part that catches people:
The grain can look fine and still have a problem.
What is falling number?
Falling number is a lab test that measures how much α-amylase activity is affecting the starch in wheat.
Here's the simple version.
Grind the sample. Mix it with water. Heat it until it thickens like gravy. Drop a stirrer into the mixture and time how long it takes to sink.
That time, in seconds, is the falling number.
Sound wheat makes a thick gel. The stirrer falls slowly. The number stays high.
When wheat starts sprouting, α-amylase becomes active. It begins breaking starch down into sugars to feed the growing seed.
The gel gets thinner. The stirrer drops faster. The falling number falls.
Bakers need that starch to do its job.
Too much α-amylase can create sticky dough, poor loaf volume, and processing problems. A load that looked like good milling wheat can suddenly become a discount problem.
And sometimes the falling number drops before you can see a green sprout.
What happens when rain hits ripe wheat?
Not every rain is a falling-number rain.
A hot dump of rain that dries by afternoon is not the same as several cool, cloudy days with repeated wetting.
The longer the head stays wet, the greater the opportunity for pre-harvest sprouting and enzyme activity.
The combination that gets my attention:
· Wheat already at or near maturity.
· Several days of rain or high humidity.
· Cool, cloudy conditions.
· Wet–dry–wet cycles.
· A crop that has been standing for some time after maturity.
That combination can increase the risk.
And here's the kicker:
You don't always get a warning from the crop. No green shoot does not mean you're safe.
Look at the germ end. Swelling. Split bran. A little crater where a root started and dried back.
Those can be warning signs. But don't rely on your eyes. Visible sprouting is not the same thing as measuring falling number.
Numbers to keep in your pocket
These are examples of the kind of numbers that matter—not universal grade or contract thresholds.
· 350 seconds: A high falling number often associated with sound milling wheat.
· 300 Seconds: This is where most elevators will start to reject or significantly downgrade
· 250–300 seconds: A range where some mills or contracts may still accept the grain, depending on specifications.
· Below 250 seconds: Falling number may become a significant marketing and quality concern.
· Very low numbers: Can create serious processing problems and may be unacceptable to some buyers.
Your buyer's specification is what matters.
A few bad kernels can be a warning. A sample can look mostly fine and still have a falling-number problem. Don't judge the truck by what it looks like from the cab. TEST THE SAMPLE.
The calendar matters
The longer wheat stands after maturity, the more exposure it has to weather.
That doesn't mean every extra day automatically lowers falling number.
It means the risk can increase as the crop stays exposed to wetting and drying conditions.
The same rain that might have been nothing earlier in the season can become a problem when the crop is ripe and conditions are right.
What should you do?
If rain is coming and the crop is ready, get serious about harvest.
I know everyone already knows this, but in case you forgot:
Standing crop dries faster than a swath lying on wet ground.
If the crop is ready, there can be a real cost to waiting.
And once the rain hits:
Keep rained-on lots separate. Don't blend and hope.
Falling number is not like simple moisture. You can't assume that mixing a bad load with a good load will solve the problem.
Blending may not restore the quality the mill needs. The buyer's testing and specifications determine what is acceptable.
Test falling number. Your eyes are not the test.
Canada: Grade versus falling number
In Canada, falling number is not itself a Canadian Grain Commission grade factor for wheat. Sprouted kernels are part of the grading system. That does not mean the contract does not specify falling number in the fine print. This is something you should ask BEFORE the contract is made.
That means wheat can still grade as milling wheat while the falling number is below what a particular mill or contract requires.
A load can look good on the grade certificate and still have a falling-number problem.
Grade is not falling number. Know both.
One more thing: LMA
There is another way falling number can drop. It's called late-maturity α-amylase, or LMA.
LMA can develop during grain filling when temperature conditions trigger α-amylase activity, even without harvest rain or visible sprouting.
So:
Cool, wet weather on ripe wheat? Think pre-harvest sprouting and falling-number risk.
Dry harvest and a low falling number? LMA may be one possible explanation.
Different problem. Same number on the lab report.
The takeaway
Harvest rain doesn't always show up as a visible sprout. Sometimes it shows up in the lab.
Sometimes it shows up in the discount. And sometimes it shows up when the mill says your wheat isn't what you thought it was. Take good samples. Keep lots separate. Test falling number.
Don't market on hope. Market on what the grain actually Is.
Thanks Greg. Insight Ag Marketing
P.S. A big Thank You to Shelly over at Paterson Grain. She suggested I remind you that not every elevator is equipped to do a falling number test and a test can take 30 minutes.
