Beat those hay-drying blues

by Kevin Shinners and Matt Digman

RAPIDLY drying hay and forage to the desired moisture for safe conservation is both challenging and frustrating. Productive and efficient cutting equipment, rapid field drying, and timely harvest with cooperative weather are all needed to achieve a high-quality forage.

Rapid drying to harvest moisture is most effectively accomplished by placing the crop in as wide of a swath as possible and by properly conditioning the crop to reduce the resistance of moisture leaving the plant. In the end, weather conditions will drive success or failure. The future of haymaking is understanding and managing this risk with decision-making tools that harness public and on-machine data.

Depending upon yield and initial moisture, between 1,000 and 1,500 gallons of water must be evaporated per acre to get the crop ready for chopping at 65% moisture. To evaporate that much water, water vapor must exit either through the leaf stomata or by diffusion through the stem’s waxy cuticle. Moisture movement through open stomata is faster than through the cuticle.

Right after cutting, the leaf stomata are open, promoting rapid water loss. However, research has shown that water vapor movement from the leaf stomata dropped dramatically within 15 to 30 minutes of cutting, and that 70% to 80% of the stem moisture remains when stomata close. When the stomata close shortly after cutting, the rate of moisture loss rapidly declines as water vapor must leave through the stem’s waxy cutin. This is why mechanically conditioning to split or break the cuticle is so important to provide faster drying.

Conditioning at cutting is widely practiced, yet the benefits are seldom fully understood. Our research group has conducted many alfalfa drying studies over the last several decades. We often will include an unconditioned control treatment. When swath width and formation were similar, conditioning always resulted in faster drying (see Figure 1). This is true whether the intended harvest practice is haylage, baleage, or dry hay. Simply put, conditioning forage crops always resulted in shorter field drying time, even to haylage moisture.

Conditioners will crack, crush, or abrade the stem so the resistance to water movement is reduced by breaks in the stem epidermis. Crimping rolls pass the crop between intermeshing, noncontacting rolls, which bend and crack the stem at intervals. Crushing rolls pass the crop through intermeshing rolls with small clearances, intermittently flattening the stem. Impeller conditioners use rotating fingers to abrade the stems. Comparisons between impeller and roll conditioners have shown that roll conditioners produce faster alfalfa drying while impeller conditioners create faster drying of grasses.

After conditioning, the most effective way to get a crop to dry faster is to place the crop in wide swaths. Laying the crop in a wide swath allows the drying crop to capture more of the solar energy, which raises the plant’s temperature to evaporate internal water. The sun’s energy increases the air’s water-holding capacity so the air surrounding the plant is less humid. Wide, uniform swaths also promote more air exchange around the plant, helping to reduce the chances of stagnant, humid air surrounding the drying plant.

The ultimate in wide swath drying is tedding the crop after a short period of wilting. Tedding not only spreads the crop to cover the whole field but mixes and fluffs the crop, which promotes air movement. More producers are using tedders, even when making haylage, to reach chopping moisture sooner.

Regardless of following best practices for haymaking, rapidly changing weather conditions continue to impair our ability to maximize hay quality. Consequently, the next frontier in haymaking is predictive modeling of crop development and drying rates. These models will combine multiple data sources such as remote and on-machine sensing with crop growth rate, drying, and weather models.

With predictive modeling, the goal is to provide a haymaking forecast. These forecasts would allow producers to perform what-if scenarios such as:

What if I cut today?

What if I tedded the crop?

How would raking the crop influence time to baling?

In addition to scheduling and what-if scenarios, the system would alert the

KEVIN SHINNERS AND MATT DIGMAN

Shinners (pictured) and Digman are agricultural engineers with the University of Wisconsin-Madison.

producer of changing conditions. As a result, these systems might suggest an intervention such as tedding, raking, or use of a preservative. Ultimately, the goal is to enable the producer to evaluate the trade-offs between missing the optimal crop maturity and weather risk, thus improving the margins in hay production.

Finally, keep these practical mowing and conditioning considerations in mind: • The purchase price of a triple mower will be about 25% less without conditioners. • Conditioners add to repair and maintenance costs and will require more fuel per acre when mowing. • A longer harvest window at the desired moisture may result from not conditioning but at the risk of longer wilting duration to reach that moisture. • Drying to baleage moisture (45% to 55%) will be much more difficult without conditioning. Getting forage to dry to hay moisture will be very difficult without conditioning. • Chopping cover crops such as ryelage is becoming more common. Conditioning helps moisture move from these thick-stemmed, slow-drying crops. • When there is no conditioner, the stems tend to lay aligned with the direction of travel. This can lead to losses when merging because the pick-up teeth easily rake through the aligned stems. Cutting at a slight angle of 2 to 3 degrees can alleviate this problem, but this is not always an option in fields that are on the contour or irregularly shaped. •

Figure 1. Second cutting alfalfa harvested with two identical mowers except that one had a roll conditioner and the other had no conditioner

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by Paul Dyk

IWALKED into a Northern Tool and Equipment store last year, which is somewhat of an unusual event. I’m not mechanically inclined, and my wife is always surprised when I can fix our dishwasher or change the car battery. I walked out with a caliper, not the fancy digital one, just a basic sliding metal caliper. Google tells me that they’ve been used for thousands of years, but it’s taken me 50 years to discover I need one.

As forage season gets rolling, there is always a discussion about particle size — factors such as knife settings, rollers, and theoretical length of cut. Inevitably, someone grabs a handful of some haylage or corn silage and the conversation goes something like this:

“How’s it look?”

“Seems about right.”

A few years ago, when photo images came back from Mars, everyone was amazed at the scenery with impressive boulders all around . . . at least until we were told these weren’t boulders but rather just small rocks on the sand. Perspective is difficult in photos unless you have a reference point. Four hundred-foot wind turbines don’t look that big until you see them next to a 90-foot silo.

Communication within a forage team is important, but how do we communicate? Texting has made the transfer of pictures easy. The person in the chopper or pack tractor can easily send pictures to the crew of a handful of silage, but does the person have the hands of the wrestling legend Andre the Giant or the basketball phenom Spud Webb?

When we use a simple reference point that everyone can see, such as the caliper, we can begin to communicate more effectively. Are the leaves coming out of the chopper at 19 or 24 millimeters (mm)? The difference (5 mm) doesn’t seem like much, but for our high-producing cattle, it can be the difference between having enough effective fiber or not. Put another way . . . it’s the difference between buying and adding one-half pound of straw to the ration to keep the cows healthy, or not. Go out and measure some particle sizes. Are you sure you could visually tell the difference between 19 and 24mm?

For the nutritionist or agronomist, we need a simple and effective method during the push of the forage harvest to communicate. There are some that might advocate the use of a Penn State Particle Separator (PSPS). Different sizes of sieves allow us to see the length of the forage. This works okay, but it has its limitations. First, the chopper operator doesn’t have a PSPS to monitor progress across a week of chopping. Second, and especially for corn silage, the results can be misleading.

From year-to-year, corn silage can range from 25% to 40% starch. Depending on moisture and processing, much of this starch may end up on the bottom pan of the PSPS. When we have a corn silage that is high in starch (40%), the bottom pan (and 4 mm screen) will be heavier. The “average” chop will seem to be smaller because of the grain, but in reality the leaves and stalks haven’t changed in length at all. When you look at the forage with a caliper, you will see the average length of leaves might be in the ideal range regardless of what the PSPS indicates.

So why not just use a standard ruler?

A ruler might work, but I’m not sure that I want a 12-inch ruler in my pocket. The small plastic ones would likely snap every time I leaned over to tie my shoes. The thing I like about the caliper is the ability to put the forage between the jaws. It eliminates any optical illusion in pictures and doesn’t leave room for errors.

The desired particle length should always be part of the forage team’s discussion before harvest begins. For corn silage, 19 to 21 mm on non-brown midrib (BMR) corn silage and 21 to 24 mm on BMR corn silage seems to work for many dairies. For haylage, it likely depends on whether it’s alfalfa, grass, or a cereal grain. The maturity of the crop also comes into play. Cereal grains are likely going to be chopped finer than haylage to ensure adequate packing. A mature sorghum-sudangrass crop is going to be chopped finer than a less mature one.

A caliper can also help when evaluating hay. It’s easy to tell the difference between a thick-stemmed, 120 relative forage quality (RFQ) hay and a bale that’s 220 RFQ, but what about two hay samples closer to the middle? Again, think of Mars. Of course, the lab analysis is likely the starting point, but if you are marketing hay, a simple, quick picture with a caliper might more effectively communicate to the end user.

They say a picture is worth a thousand words. Adding a caliper to your photo may just offer some additional text and perspective. •

PAUL DYK

The author is a dairy nutrition consultant with GPS Dairy Consulting LLC and is based in Malone, Wis.