Balancing Alfalfa Yield and Quality
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By Dan Wiersma and Ev Thomas
Alfalfa quality depends on a number of factors, and weather is a major one. Once alfalfa genetics have done their best with what Mother Nature has provided, it's up to the grower to preserve as much of the nutritional quality as possible. The first cutting of the season is the most significant. As much as half the season's total yield can be from the first cutting.
Growers should try to balance yield with quality. Generally, quality is highest when alfalfa plants are younger. As they grow, they add tonnage, but nutrient density begins to drop. We can use systems such as the Predictive Equation for Alfalfa Quality (PEAQ) tool to monitor quality changes.
A Nutrient Peak
Try to harvest when the RFQ is high: 180 to 190. The crop will begin to lose some quality as soon as it's cut. Good harvest management can result in a final RFQ of 150 to 160 or higher.
The goal after cutting is to minimize losses. Most growers now swath and lay alfalfa into wide windrows. This provides more surface area for rapid drydown of the crop.
Again, balance is the key. Plant moisture levels at swathing can be more than 80%. It needs to dry down to 60% to 70%. This can take 24 hours under normal conditions. If you get too much heat and wind, plants can get too dry. With excessively dry haylage, leaves, the most nutrient-rich part of the plant, can separate from the stems and be lost when merging and chopping.
Merge windrows for chopping not more than an hour or two before the chopper picks the alfalfa up (depending on field conditions). If the crop is too dry, you may see aerobic stability issues. If it's too wet, you may battle fermentation issues.
Protect Alfalfa Quality
Preservation starts at the chopper. Applying a high-quality inoculant can drop pH levels and initiate the fermentation process. Inoculants such as Pioneer® brand 11H50 help limit nutrient losses. Pioneer brand 11AFT also drops pH and helps preserve nutrients on the front end. It also helps break down bonds that hold lignin, cellulose and hemicelluloses together. This frees more nutritional value, resulting in faster and better digestion of these energy sources.
Another key management factor is how a grower packs alfalfa. A tight, dense pack helps limit aerobic activity. Get chopped silage to the silo or bunker as promptly as possible. Then pack properly. A rule of thumb is to have 800 pounds of tractor weight for each ton of silage delivered per hour. Pack in thin layers, no more than six inches at a time.
Paying attention to harvest timing, especially during the first cutting, can improve the quality of the alfalfa in the bunker. Then good management can preserve the lion's share of those nutrients through feedout.