How Moisture Impacts Barley

Have you heard about the acronym FAT TOM? It's a food safety shorthand for those in the food production and food-grade crop industries. It refers to the factors and conditions that allow bacteria and other contaminants to grow, which can lead to food spoilage.

What does FAT TOM stand for?

• Food
• Acidity
• Time
• Temperature
• Oxygen
• Moisture

When growing crops like barley, conditions are prime for mold and microbial growth that can lead to financially devastating spoilage. While some of these factors are beyond the control of growers, moisture is one element that can be carefully monitored to avoid conditions that can spoil an entire harvest.

Here's how moisture can impact your barley crop, and why it matters so much.

Barley, Harvest Time, and Ideal Moisture Levels

No matter what kind of crop, maintaining high-quality grain is all about the correct harvesting, grain management, and crop storage once it has been removed from the field. When should barley be harvested? At what moisture level can barley be safely stored or primed to capture the best price at the market?

The easiest solution for harvesting barley is to wait until the grain is fully ripened and reaches a moisture content level of 12% or less. When growers can harvest barley at this moisture content level, it can be directly delivered for storage or sale. When the crop is ripe, it's a good idea to harvest as soon as possible to avoid field losses from wind or weathering.

This process is referred to as direct heading, and it's definitely the most cost-effective method to harvest barley. However, there can be long periods of high humidity or heavy rains in which the harvesting of truly dry barley just isn't possible. This can lead to all kinds of delays and field losses, even grain discoloration from summer rain.

On the other hand, waiting too long to harvest brings its own problems. As the crop dries down, over-threshing and rough handling can loosen or strip the husk. This problem is known as skinning.

Skinned and broken barley kernels caused by over-drying and over-threshing can bring a much lower cost at the market, especially for malting barley. This is because skinned barley absorbs moisture faster than intact kernels, which can lead to the death of the grain. For brewers who use barley, this means a lower alcohol yield (and therefore lower profits).

Essentially, too much moisture and barley can spoil. Too little moisture and farmers can't get the best price. That’s why measuring moisture correctly is essential.

What Happens When Barley Needs to Be Harvested at Other Moisture Levels?

Not every growing season will allow farmers to harvest barley under perfect conditions. When the unexpected happens, growers need to monitor moisture levels and account for current conditions. Often, this involves early harvesting and drying.

Barley is physiologically mature at approximately 35% seed moisture, but it is by no means ready to harvest at this point. At 20% to 30% moisture, growers can swath their barley crops to allow them to dry before combining. Swathing, also called wind-rowing, refers to speeding up the grain drying process by cutting the crop when it reaches maturity, bundling it into swaths, and allowing it to dry before harvesting.

Additionally, to limit harvesting delays, barley can be direct-harvested at moisture levels above 12%. This moist grain needs to go through aeration to maintain quality or pass through a grain dryer to reduce moisture levels to where crops can be safely stored. Either way, this comes with a cost.

Malting barley can be harvested when the moisture levels reach 18%. At higher moisture levels, it can be a challenge for harvesters to thresh barley grain from the head. Taking aeration, drying costs, and other practicalities into consideration, the optimum moisture content for harvesting barley is around 14% to 15%.

From swathing at 20% to 30% moisture to harvesting anywhere between 12% and 15% moisture and then selling or storing barley, being in tune with the moisture content is crucial at each step of the process. In the field, the pocket-sized FV201 Handheld Grain Moisture Tester gives an accurate reading in about three seconds, works in any orientation with no stable surface required, and ships with a barley calibration. At receiving or on trucks and rail cars, the PM650 Advanced Grain and Seed Moisture Meter handles larger samples and a far wider calibration range without husking or grinding.

For fast, large samples, the PQ520 Single Kernel Grain & Rice Moisture Meter, which ships with wheat, barley, and rice calibrations, offers fast, continuous moisture measurement, determining the moisture distribution of a large sample in minutes, and can process a 300-kernel set in only two minutes. This can give growers an idea of how moisture is distributed across a sample gathered from multiple points in the field.

Drying Barley Without Wrecking Malting Quality

Getting barley off the field is only part of the job of bringing your crop to market. When it comes off wetter than the safe storage range, it has to be dried. For malting barley, how you dry it matters as much as whether you dry it. As a general rule, barley combined above about 13.5% moisture needs artificial drying to hold its quality in storage.

Natural-air and low-temperature drying usually costs less at the same time that it protects malting quality, when compared to high-temperature drying. High-temperature drying, if it isn't carefully monitored, can lower the test weight, reduce germination, and cause cracks in the kernels that lead to breakage during handling. Because germination is the entire point of malting barley, 100°F is the maximum recommended temp for air drying barley.

One important caveat: Right after high-temperature drying, the outside of each kernel is drier than the inside, which can make electronic moisture meters read low until the kernel equilibrates. To confirm a reading, seal a sample in a plastic bag for about 12 hours to let the moisture even out, then measure again.

Safe Storage: Moisture, Temperature, and Time

Once barley is in the bin, you want to keep it appropriately dry. For clean, sound barley going into storage during warm weather, about 12% moisture is the recommended maximum. If it’s kept cool, it can be a little bit wetter than that 12% rate, but drier, cooler barley will keep longer.

Temperature and time work hand in hand with moisture. Aeration is one of the most effective tools you have for protecting your crop. The allowable storage time roughly doubles for every 10°F you cool the grain (and for about every two-point drop in moisture). Insect activity slows below 70°F and largely stops around 50°F.

Importantly, aeration cools grain, but it doesn't dry. Because little to no drying happens during a cooling cycle, aeration is no substitute for a drying process. After barley is binned, check it at least every two weeks through the fall until it's cooled, then at least monthly through the winter, watching for small changes in temperature or moisture that can signal trouble ahead.

Instrument Specs at a Glance

The PM650, PQ520, and FV201 all read moisture without husking or grinding, and all three hold ±0.5% accuracy under 20% moisture. They differ in method: the PM650 and PQ520 measure by capacitance, while the pocket-sized FV201 Riceter uses electrical resistance, so it needs no stable surface or internal scale and works in any orientation for true in-hand field testing.

Here's how they compare:

FV201 Handheld Grain Moisture Tester

• Best for: true in-hand field testing, no stable surface or scale required, works in any orientation
• Measurement principle: electrical resistance
• Moisture range: 10-30% (wet basis, sample dependent)
• Accuracy: ±0.5% (standard error of calibration over 10-20%); resolution 0.1%
• Response: about three seconds, twist-and-read
• Calibrations: 6 factory calibrations (brown rice, milled rice, paddy, barley, naked barley, wheat)
• Portability: pocket-sized, 0.44 kg (under 1 lb), 4 AA batteries

PM650 Advanced Grain and Seed Moisture Meter

• Best for: larger-sample checks at receiving or on top of trucks and rail cars
• Measurement principle: capacitance (dielectric)
• Moisture range: 1-40% (product dependent)
• Accuracy: ±0.5% (under 20%); resolution 0.1%
• Calibrations: 150 factory calibrations
• Response: instant, with no husking or grinding
• Portability: battery-powered handheld, under 1.5 kg

PQ520 Single Kernel Grain & Rice Moisture Meter

• Best for: seeing how evenly moisture is distributed across a lot
• Measurement principle: electrical capacitance, one kernel at a time
• Throughput: a 300-kernel set in about two minutes
• Reads out: average moisture, kernel count, and a moisture-distribution histogram
• Accuracy: ±0.5% (under 20%); resolution 0.1%
• Capacity: 10-1,000 kernels per sample
• Calibrations: ships with wheat, barley, and rice

Frequently Asked Questions

What's a safe moisture level for storing barley?

For clean, sound barley stored in warm weather, about 12% is the recommended maximum. You can store it a little wetter if it's kept cool, and you'll want it drier still for long-term storage.

Can I harvest barley before it's fully dry?

Yes. Malting barley can be combined up to about 18% moisture, but anything above roughly 13.5% needs drying before it goes into storage, and threshing damage climbs as moisture rises past 18%.

Why does over-drying cost money at the market?

When barley gets too dry, the husk loosens and kernels skin or break during threshing and handling. Skinned and broken barley is downgraded, especially for malting, so over-dry grain can fetch a lower price.

How can I check moisture quickly in the field?

A pocket-sized handheld like the FV201 Riceter reads barley moisture in about three seconds and works in any orientation, ideal for in-hand field checks. The PM650 covers the same job with a larger sample and a wider calibration range when you are also testing beans or other seeds.

How do I tell whether moisture is uneven across a lot?

A single-kernel meter like the PQ520 measures a 300-kernel set in about two minutes and displays the moisture distribution, so you see the spread across the sample rather than just an average.

Kett has the laboratory-grade test instruments you need to manage your barley crop from swath to storage or market. If you want to learn more about the instruments we offer that can guide you through harvest, contact our experts today.