Besides diminishing palatability, dirt increases the ash content of any hay or forage ration. Ash directly displaces nutrients because cattle cannot transform it into energy. For example, if a cow consumes 1 pound of ash over the course of a day, that is the same as removing 1 pound of beneficial feed that it could convert to bodily growth or milk production.
Natural minerals, such as calcium and magnesium, occur in all forage plants. These are technically classified as ash, even though many of them benefit the animal. As much as we try to avoid it, some unwanted soil will inevitably stick to the plants from dust, rain splash and touching the ground. So how can we minimize the levels of undesirable ash contamination in a feeding ration? Carefully chosen harvest practices and equipment adjustments will go a long way toward delivering high-quality nourishment to your animals and maximizing your operation’s profitability.
Mowing
As the first step in the forage-harvesting chain, mowing plays a pivotal role in reducing ash levels. Most operations today utilize a disc mower or mower-conditioner. These machines offer outstanding speed and field efficiency. However, without some simple adjustments, they can contribute to elevated ash levels.
First, take a look at the knives. Angled or curved knives, combined with the rotating discs, create upward suction. This suction helps any downed hay to stand up enough to be cut, but it also lifts dirt into the crop, especially in drier conditions. Flat-bladed knives do not generate as much upward lift and take up less dirt.
The mower’s cutterbar setting also affects the amount of dirt pulled into the cut crop. Be sure to keep the angle of the cutterbar as flat as possible. If the cutterbar is tipped too far forward, it will force the knives to scalp the soil surface. While some crops such as alfalfa can be cut down to 1.5 inches to maximize yield, cutting low tends to increase ash contamination by bringing up more dirt when harvesting the plants. Raising the stubble height to 3 inches does lower yield slightly, but more than makes up for it with lower ash levels. The taller stubble forms a better “bed” on which to lay the cut crop, helping to keep it from contamination.
Finally, widening the swath or windrow can improve ash levels. Packing all of the cut crop into a narrow, heavy windrow usually causes it to sink through the stubble and sit directly on the ground. A wider swath will spread the weight of the cut crop across a larger surface area, helping it sit on top of the stubble.
Tedding and raking
Much like wide swathing, tedding can help lower ash levels by spreading out the crop as much as possible so it rests on top of the stubble. Make sure to set the tedder properly. The tines should sweep just below the top of the stubble so they displace as much crop as possible without brushing the ground and incorporating dirt into the forage.
When the time comes to gather the crop into final windrows for harvesting, the style of rake significantly influences the ash level of the forage. Wheel rakes offer low purchase prices and simple designs that seem very attractive on the surface. They can be the right fit for some operations, but despite these advantages, they are the least favorable option from an ash-content standpoint. The rake wheels roll the crop across the stubble. Without a powered drive system, the rake wheels must constantly contact the ground, stirring up dirt and dust, which can be incorporated into the windrows. All other factors being equal, forage gathered with a wheel rake may see twice as much additional ash content compared with that gathered with a rotary rake.
Rotary rakes, when set correctly, keep their tines just above the soil surface as they move the crop. Since the tines do not contact the soil, they keep harvested forages much “cleaner” than wheel rakes do. However, the tines still move the crop across the ground, allowing stems and leaves to collect contaminants as the windrow is formed. This method of creating windrows means that rotary rakes will deposit extra ash into forage rations as opposed to hay mergers.
Pickup-style mergers are designed for the cleanest operation of all hay-gathering options. The pickup tines of a properly set merger reach just below the top of the stubble without contacting the ground, bringing the cut crop straight up onto the belt. The belt then transfers the crop and drops it straight back onto the ground. Carrying the crop on the machine rather than moving it laterally on the ground keeps the material from picking up dirt, again, minimizing ash content.
Final thoughts
All crops harvested and fed to cattle will contain some level of ash above what occurs in nature. Unavoidable weather conditions and other factors mean that no forage will be completely free of dirt. The best way to reduce ash is to focus on equipment-related factors that you can control throughout the harvesting process. Since ash displaces beneficial nutrients, anything you can do to remove it from the ration will improve the animals’ performance and make a positive impact on your operation’s bottom line. 
Philip Loduha is a Kuhn North America product management specialist.
PHOTO: Pickup-style mergers are designed for the cleanest operation of all hay-gathering options. Photo courtesy of Kuhn North America.
