Alfalfa quality varies from year to year because of many factors, including maturity, age of stand (grass content), moisture, fermentation and palatability. To produce the best possible quality, Dann Bolinger, DuPont Pioneer dairy specialist, suggests growers focus on three things they can control: maturity, harvest timing and chop height.
1. Maturity Issues
Maturity has a tremendous influence on the nutritional value of alfalfa. In fact, growing environment and harvest maturity affect alfalfa more than genetic differences. Bolinger says the four biggest environmental factors impacting alfalfa quality are temperature, water deficiency, solar radiation and soil fertility.
Warmer temperatures accelerate neutral detergent fiber (NDF) development and lignification, which decreases quality and digestibility. Thus, forages grown in northern areas where nights are cooler tend to be higher in quality.
Drought conditions can limit yields but they tend to result in superior nutritional quality: Protein level and digestibility are higher because of a higher leaf-to-stem ratio. Unfortunately, dry conditions usually mean higher temperatures that increase lignification and threaten quality. Hot and dry weather generally results in better-than-normal alfalfa quality. Quality generally is best in cool and dry conditions.
Solar radiation or light promotes both yield and quality, Bolinger explains. Sunny weather increases carbohydrate production, improving digestibility (quality) and photosynthesis (yield). Cloudy weather does just the opposite, decreasing both yield and quality. In fall, as daylight diminishes, digestibility may increase thanks to cooler temperatures.
2. When to Cut
Determining the time of day to harvest is a challenge. Some growers cut later in the day because crops are able to lay down more sugars (energy). This improves palatability and helps with silage fermentation. However, research is unclear about whether differences exist after drying and/or fermentation.
When harvesting for silage, morning cutting in general works best, Bolinger says. When mowed in the morning, alfalfa usually is ready for harvest about nine hours later. When mowed in the afternoon, alfalfa generally isn’t harvestable until the next afternoon. This may expose the crop to weather risks.
3. Setting Chop Height
Lowering the cutter bar increases yield. Research shows cutting for a 1- to 2-inch stubble height results in higher yields with little or no damage to the plant. Any lower, and equipment can damage the crown buds and curb regrowth.
However, cutting at this low level can allow disc mowers to pull soil into the harvested crop, a practice that hurts digestibility and increases the potential to pick up soil-borne bacteria and spores that hamper fermentation.
For most producers, a 2.5- to 3-inch height is a good compromise. The exception is the final harvest of the season in regions that face cold winters. In these situations, it’s best to leave 4 to 6 inches of stubble to ensure good insulation for the crowns
The foregoing is provided for informational purposes only. Please consult with your nutritionist or veterinarian for suggestions specific to your operation. Product performance is variable and subject to a variety of environmental, disease, and pest pressures. Individual results may vary.