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Effectiveness of equipment to speed hay drying

Alan Rotz Published on 01 April 2011
raking hay

High-quality forage is recognized as an important requirement for maintaining maximum production of cattle, particularly in dairy production.

 Adequate roughage is needed in diets to provide good rumen function, but as more roughage is fed, the energy density of the diet is reduced.

High-quality forage allows the animal to consume adequate forage while increasing energy intake to maximize production. The greatest obstacle to producing high-quality hay is rapid field curing.

Good drying conditions are important and often difficult to obtain. Adequate periods without rainfall are sporadic and hard to predict.

Although processes are available to speed hay drying, they must be used along with good drying weather to be effective.

Equipment and processes have been promoted to make better hay, but few have proven to be effective tools.

Although high-quality hay production is a challenge, there are practical steps that can help. Using the right process at the right time is important.

Conditioning and tedding treatments can speed drying, but such processes also cause loss. Dry matter loss and nutritive changes occur each time a machine passes through the crop, reducing the quality of the final product.

Although some loss is inevitable, good management can reduce or compensate for these losses to provide the quality forage needed.

The benefits received from these treatments or processes must be weighed against the added costs to determine the best procedures for haymaking on your farm.

Hay drying
The need for rapid wilting or drying of forage crops in the field is well recognized, but accomplishing this task remains a challenge.

Many factors affect the field-drying rate of forage. Drying is restricted by the structure of the plant, swath structure and soil and weather conditions.

The most restricting factor varies throughout the drying process and with crop management. When a high-yield crop is laid in a narrow swath, the swath tends to be most limiting because the moisture cannot readily move out of the swath.

When forage is spread in a thin swath, the movement of moisture out of the plant can become limiting. Under these circumstances, conditioning of the crop is most beneficial in allowing moisture to leave the plant more easily.

In temperate climates, weather is often the most restricting factor in drying. Of all weather influences, solar radiation level is the most important.

This energy from the sun is required to evaporate and move moisture out of the plant. The drying of hay requires the removal of about three tons of moisture for every ton of hay produced.

This requires 7 billion joules of energy, which is the equivalent of 70 gallons of fuel oil. In haymaking, we are fortunate that free energy from the sun can be used to carry out this process.

Warm air temperature and low humidity also aids drying, but the sun is the primary driving force. Wet soil under the swath also slows drying by allowing moisture to move up into the swath.

Dry matter (DM) losses and quality changes occur while the crop is wilting or drying in the field. These include plant respiration, rain and machine-induced losses.

Plant respiration is a natural process that continues after the plant is cut. Respiration converts carbohydrates stored in the plant tissue to carbon dioxide, heat and moisture that leave the plant, causing a DM loss.

Plant respiration ceases when the crop dries to a moisture level below 40 percent, so rapid drying early in the field-curing process can reduce this loss.

Since this loss is primarily readily digestible carbohydrates, the loss increases the fiber content and reduces the energy content of the forage.

With rapid drying, this loss is less than 5 percent, but it can be excessive when drying conditions are poor.

Rain damage, when it occurs, can have the greatest effect on loss and quality. Rain causes loss by knocking off leaves and leaching soluble nutrients from within the plant tissue.

Since leaves are normally higher in nutrient concentrations than stem parts, the loss of leaves reduces the quality of the remaining forage.

The greater loss, though, is the less visible loss from leaching. Soluble carbohydrates, proteins and minerals are washed from the plant material, leaving a higher fiber concentration and lower energy content.

In general, the greater the amount of rain and the drier the crop at the time of the rain, the greater the loss of dry matter and nutrients.

The goal is always to avoid rain damage, but when it occurs, it is better to have it early in the drying process rather than about the time the crop is ready to bale.

This is somewhat beyond our control, but the producer can be less concerned about rain the day of mowing if better weather lies ahead.

Mowing equipment
Producing high-quality forage begins when the crop is mown. Forage crops should be mown at the right maturity to optimize yield and quality.

Quality in most forage crops declines rather rapidly as the crop enters a reproductive stage of development and growth begins to slow.

The optimum maturity varies among forage species, but normally this optimum occurs in the late vegetative to early reproductive stages.

Mowing at this time provides a good yield, a relatively low fiber content and adequate energy and protein contents.

A challenge in hay production is to obtain this quality level at a time period when weather conditions are suitable for drying the crop.

When heavy rain and poor drying conditions are expected, it is normally best to delay. If the forecast is light rain or a brief thunderstorm with adequate- to-good drying conditions ahead, it may be best to proceed with mowing.

The loss in quality may be greater by delaying harvest than that caused by rain.

There are several mower designs available for cutting forage crops, the primary types being cutterbar and rotary disk mowers.

The type of mower used has little effect on drying, mowing losses and the resulting forage quality. Rotary mowers tend to have a higher power requirement and thus require a larger tractor and more fuel to operate.

With a higher mowing capacity though, less time is required, offsetting some of the increased fuel use and reducing labor required.

Even though the purchase price of rotary mowers is a little higher for a given width of cut, the overall cost of mowing is similar between these major mower types.

Conditioning to speed drying
Mechanical conditioning treatments are often used in speed drying; these can be categorized as either roll or flail conditioners.

Rolls smash or break the plant stems, and flails abrade the waxy surface of the plants and break stems. Both processes can improve drying, but for alfalfa, roll devices are more effective with less field loss.

Some roll designs are promoted for faster drying, but field and laboratory studies consistently show little or no difference in the drying of alfalfa or grass treated with commonly used crushing roll designs.

Roll conditioning is most effective on a thick-stemmed crop such as an early cutting of alfalfa. Flail-type conditioners are better suited to grass crops, and they provide a greater throughput capacity when harvesting high-yielding or entangled crops.

Adjustment of the conditioning mechanism can affect drying. Roll clearance and pressure often can be adjusted. A minimum clearance must be maintained.

If the clearance becomes too close, excessive damage and loss of plant particles occurs. With too much clearance, plant material flows between the rolls with little crushing.

Too little or too much pressure on the rolls has similar effects. On flail-type conditioners, the clearance between the rotating flails and a stationary bar can be adjusted to control the amount of breaking and abrasion that occurs.

Dry matter losses and the associated nutrient changes caused or promoted by conditioning increase with crop maturity and the severity of conditioning.

Although more severe conditioning can provide faster field curing, harvest losses are generally greater. Normally moderate conditioning is recommended to obtain adequate drying with relatively low loss (1 percent to 2 percent of yield).

This relatively low loss has little effect on forage quality.

A chemical treatment, referred to as a conditioner or drying agent, can be sprayed on alfalfa at mowing to help speed drying.

The chemical affects the waxy surface of the plant to allow easier moisture removal. Chemical conditioning works well with mechanical conditioning because it is most effective on crops where mechanical conditioning is least effective.

The treatment can double the drying rate of the crop when used under good drying conditions with the crop dried in a relatively thin swath. On the average, this increase reduces field-curing time about half a day.

Swath manipulation to speed drying
As forage dries in the field, the top of the swath dries more rapidly than the bottom. Manipulation of the swath can speed the drying process by moving the wetter material to the upper surface.

Swath manipulation can also improve drying by spreading the hay over more of the field surface, increasing exposure to the radiant solar energy and drying air.

There are three operations used in haymaking to manipulate the swath: tedding, swath inversion and raking.

Tedding can be used any time during field curing, but it is best to do so before the crop is too dry (above 40 percent moisture content).

The stirring or fluffing of forage typically reduces field-curing time up to half a day. Tedders are sometimes used to spread a narrow swath formed by the mower-conditioner over the entire field surface.

When done soon after mowing, the average field curing time is reduced up to two days compared to drying in a narrow swath.

In addition to speeding drying, tedding also tends to create more uniform drying, so wet spots in the swath are reduced.

Disadvantages of tedding include increased losses and increased fuel, labor and machinery costs.

When tedding is done on a relatively wet crop (above 50 percent moisture), the resulting loss is less than 3 percent; however, applied late in the drying process, the loss can be more than 10 percent. Tedding will also increase raking loss.

Spreading the hay may promote bleaching of hay color. Bleaching does not necessarily affect the nutritive value of hay, but it often affects the market value.

When the costs of performing the tedding operation are compared to the benefit received, routine use of tedding is difficult to justify, particularly for alfalfa. Occasional use under difficult drying conditions may bring greater economic benefit.

Swath inversion machines have been used that gently lift and invert the swath. Exposing the wetter bottom of the swath speeds drying, reducing the average field-curing time a few hours.

Swath inversion is not as effective for improving drying as tedding, but shatter loss is very low. With less drying benefit, there is less potential for reducing rain and respiration losses.

The added labor, fuel and machinery costs of the operation are generally greater than the benefit received.

Raking is another form of swath manipulation. Raking tends to roll the wetter hay from the bottom of the swath to the outer surface of the windrow, which improves drying.

Following the initial improvement, the increase in swath density can reduce drying rate, so crop moisture content at raking is important.

Raking also causes loss, and the loss is related to crop moisture (2 percent when wet to 15 percent in very dry crop).

The best moisture content to rake for low loss and good drying is between 30 and 40 percent. In dry weather periods, hay can be raked in the evening or early morning when leaves are moist and less prone to shatter.

Raking at the proper time can reduce field-curing time a few hours to allow an earlier start at baling. A substantial economic benefit can often be obtained by rolling swaths together to allow large balers or forage harvesters to operate more efficiently.

Baling high-moisture hay
Another option for shortening the field curing time is to bale hay before it is fully dry. Baling moist hay may reduce raking and baling losses, providing an increase in harvested yield and harvested quality.

However, moist hay deteriorates rapidly in storage, offsetting the benefit of reduced field losses unless treated to enhance preservation.

Additives commonly used for the preservation of high-moisture hay include propionic acid, organic acid mixtures, buffered acid mixtures and microbial inoculants.

Feeding considerations
For the commercial hay producer, high-quality hay is important every time hay is made. When hay quality suffers for any of the above reasons, the economic value of the hay decreases and this affects farm profit.

Thus, commercial hay production requires good management at all times, and techniques for assuring quality may be more cost-effective than they would be for the livestock producer.

When hay is produced for on-farm use in feeding cattle, forage quality can be less important. This assumes, though, that good management is used to feed the highest-quality forage to the animals requiring that quality.

For dairy animals in early lactation, the highest- quality forage is needed to maximize their intake. Maximizing intake during this crucial stage will allow animals to peak their production at a high level.

For other animals, including those in the last half of their lactation, early dry cows and yearling heifers, forage quality is less critical.

Thus, producers feeding animals must focus on producing or buying the best forage they can obtain for their critical groups while reserving lower- quality forage for other animals.

Concentrate on making some of the best forage you can and feeding it appropriately, and do not worry about the times you fail. Some lower- quality forage can also be used quite effectively on the farm.  FG

References omitted due to space but are available upon request.
—Excerpts from University of Wisconsin Extension Forage website

Al Rotz


C. Alan Rotz
Agricultural Engineer