The Lowdown on When and How to Mow a Hay Field
July 2022
When mowing forage for hay, numerous management decisions contribute to total crop yield, forage quality and crop stand longevity. This includes whether you’re harvesting grass hay or alfalfa hay, your preferred cutting height and when the first cutting takes place. In addition, mower selection and maintenance can also impact your operation in terms of productivity and profitability. This article explores some of the crucial decisions that should be considered before hooking up your mower, hitting the field and making your first cut of the hay season.
When to mow a hay field
Maturity stage at harvest is the single most important factor influencing the quality of your forage, according to the University of Massachusetts Amherst (UMASS) Extension. This is because as forage crops mature, fiber content increases and quality diminishes. Therefore, striving for maximum yield can come at the expense of quality.
The UMASS Extension report states that, “When producing forages, especially legumes, if the goal is (achieving) the highest quality, this will tend to shorten stand persistence and decrease yield. Maximum yield of alfalfa is achieved at the stage of full flowering, whereas quality is highest prior to flowering.”
When to cut hay
According to Iowa State University (ISU) Extension, harvesting more frequently produces forage of higher nutritive quality at an acceptable yield level, but negatively impacts stand vigor and longevity. Conversely, harvesting less frequently will produce acceptable yields and a greater degree of stand persistence and plant vigor, but forage of a lower nutritive value.
In order to maximize dry-matter yield, Iowa State recommends a “three summer-cut system,” which means a first cutting at nearly full bloom and harvesting subsequent cuttings at 40 to 45 day intervals until late August or early September (this time period can vary based on climate). A “four summer-cut system” can help strike a balance between maximizing forage quality and dry-matter yield. For this, Iowa State recommends harvesting the first cutting at the late-bud to first-flower stage and harvesting subsequent cuttings at 32 to 35 day intervals until late August or early September.
Setting the right cutting height
Studies performed by University of Wisconsin Extension showed that forage yield increases as cutting height is reduced. For instance, on average, total alfalfa yield increased by 0.5 tons dry matter per acre for each 1-inch reduction in cutting height. Forage quality, however, decreased as cutting height was reduced.
In order to maximize forage quality and dry-matter yield on subsequent hay field cuttings, Vermeer recommends a cutting height of 3 inches for alfalfa and 4 inches for grasses. The reason for this is the main growing point for grasses is above the ground, so cutting below 3 inches means it will take longer for the crop to regenerate, which limits the yield of the next cutting.
With alfalfa everything below 3 inches is mostly stem. The leaves which contain all the nutrients stand at 3 inches and above, so cutting lower means you get a little higher yield, but no additional nutrients for your cattle.
A lower cutting height could lead to greater amounts of ash and rocks in the crop, giving producers yet another reason to select a higher cutting height. To minimize dirt and ash contamination and achieve a clean cut of the crop, it’s best to keep a close eye on the pitch of the cutter bar. Some operators tend to set the pitch of the cutter bar downward at too steep of an angle. On Vermeer trailed mowers, we recommend angling the cutter bar upward to get a cleaner cut.
Choosing the right mower
The size and type of mower you want are the top things to consider when purchasing a new mower. In recent years, there has been a trend of producers moving from traditional three-point mowers to trailed mowers, which require less horsepower and give producers added flexibility.
The main knock against three-point mowers is that they tie up extra tractors, extra operators and consume extra fuel. Larger trailed mowers allow producers to increase mowing capacity while reducing fuel consumption, maintenance and labor costs.
Plus, easy hook up and transport features (like the two-point Quick Hitch system and hydraulic folding capabilities) on the Vermeer TM1210 and TM1410 trailed mowers make them simpler to use.
Don’t forget mower maintenance
For those of you who already own a mower, you can turn your attention to preseason maintenance. Be sure to check your owner’s manual for daily and regular service and maintenance needs to optimize the performance of your mower. The Vermeer tech specialists offered some tips for inspecting your mower.
Lube: Oil and lubrication points should be inspected regularly. The gearbox oil, driveline and PTO shaft are particularly important. Make sure the PTO slides in and out smoothly, otherwise you risk breaking off the shaft.
Cutter bar: Check the cutter bar to make sure it’s functioning properly. You should be able to spin the cutter bar around with one hand. If you can’t spin it, look under each of the discs to make sure there is no buildup of twine or other material.
Tires: Check the tires to make sure they are adequately inflated.
Blades: Make sure all blades are attached and in good shape. Replace any broken or excessively dull blades.
Sources cited:
http://www.uwex.edu/ces/forage/wfc/proceedings2001/alfalfa_cutting_height.htm
