How windrow width impacts hay quality


PROGRESSIVE FORAGE GROWER – Losses begin at cutting: That’s the most basic hay and forage fact in relation to quality. Once the blade slices a hay stem, the quality race is on!

The fundamental problem with haymaking is that it’s impossible to preserve all the quality found in a standing crop. Once mown, the metabolic and weathering losses can significantly impact crop quality. The faster hay can be cured and put up, the higher the quality that is preserved.

One of the most recent quality haymaking developments has been the study of swath widths and crop drying rates. For many years prior to the mechanization of haymaking, producers laid hay in wide, unconditioned swaths and made additional passes with conditioners and rakes to gather the hay into harvestable windrows.

In the mid-1960s, with the advent of mower-conditioners, haymakers began to fully mechanize their harvest and utilize new technology to harvest, store and utilize hay crops faster and with greater efficiency. Industry then focused on the influence of conditioning first when discussing drying, and the influence of swath width was overlooked.

The mid-2000s brought the advent of speculative “hay-in-a-day,” much conjecture and a resurgence of wide swathing practices. Recent university research and industry collaborations have contributed to a renaissance in haymaking machines. New hay machinery models can provide more uniform conditioning as well as the formation of fast-drying, wide swaths.

To understand the resurgence of the wide swath and these new machinery advances, it’s important to review how a hay crop dries. Most often, the drying process is reflected as having three phases: leaves, surface moisture and stems. The following descriptions of these three drying stages were adapted from a Focus on Forage paper by Dan Undersander and Craig Saxe, University of Wisconsin Extension:

Stage 1: Leaves

The first phase of moisture loss is through open stomata. Stomata are little cells that act as doors to allow the exchange of moisture and gasses between plants and the atmosphere. An important thing to remember about stomata is that they are only open when exposed to sunlight. Laying a wide swath exposes more of the stomata to sunlight so they remain open, permitting more rapid initial drying.

That’s the first step in achieving faster drying – laying the crop out wide to “soak up the sun.” University studies indicate that rapid drying of this initial 15 percent of moisture can preserve starches and sugars, and result in feed with more total digestible nutrients (TDN). Preserving more value in the crop is the first step in producing higher quality forage.

Stage 2: Surface

The second phase of drying is moisture loss from the plant surfaces. At this point, plant moisture is at or below 60 percent and the stomata have closed. If haymakers choose traditional rubber rolls, steel rolls or flail-tine conditioning, the advantage of mechanical conditioning occurs during this phase. Mechanical conditioning creates artificial openings in the plant to allow moisture to escape easily, and that means faster drying.

Stage 3: Stems

The third and most critical drying stage for the production of dry hay is the loss of tightly held moisture. This is moisture trapped in the stems and plant structures. At this stage, mechanical conditioning is essential. Without mechanical conditioning, this moisture would be trapped by the plant structure and drying would slow dramatically. By crimping, cracking and striping away the cuticle wax layer, tightly held moisture is allowed to escape from the stems, continuing the drying process.

In summary, quality hay comes down to remembering that the quality of hay and silage crops is determined by what happens immediately after cutting. Swath width and conditioning adjustments are variables that haymakers can control, whereas weather will always be an uncontrolled variable. Improved forage quality comes from taking steps to impact the variables you can control in a positive way.  FG

By Jordan J. Milewski, marketing manager of crop preparation for New Holland.

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