While the year started with slower growing degree accumulation the warm weather over the last couple of weeks, has rapidly progressed forage maturity. Harvesting forages at the proper time for the livestock you are feeding is critical to farm profitability. Poor quality forages must be supplemented to maintain livestock. In the southern part of the state, some forage grasses are in head while in the northern part of the state, barnyard grass is in head. Most are still in the vegetative stage but will be in head within a week, even though they do not look tall enough to be in head.
Winter annual cereal grains for forages may also be more mature than they look from the field edge. In the southern half of the state, heads are starting to emerge, while in the northern part, the flag leaf of cereal rye has emerged. Scouting these forages is critical, as digestibility and crude protein decline rapidly as they mature. The ideal harvest time to maximize yield and quality is just after the flag leaf emerges so that the forage is harvest before the head emerges from the boot.
Harvest decisions for alfalfa are primarily based on maturity; however, this method can be misleading due to climatic variations affecting the rate of bud and flower development for first cutting. 21-inch tall alfalfa in the vegetative stage has similar digestibility to 19 inch alfalfa that is in the bud stage.
Spring changes of alfalfa %NDF can increase about 5 percentage units each week. Therefore, it is imperative for growers to be monitoring their alfalfa for optimal harvest times. Traditional wet chemistry remains the best method to measure %NDF; however, these traditional methods are often too time consuming when a rapid estimation of NDF is needed to make harvest decisions.
Growers can easily measure %NDF in their fields using a method referred to as PEAQ, Predictive Equations for Alfalfa Quality. This method uses max height and max stage of a pure standing alfalfa crop to determine %NDF. Neutral Detergent Fiber estimations using this method can begin as soon as the alfalfa crop reaches at least 16 inches in height. The protocol for utilizing PEAQ in the fields can be found here and short video describing the method can also be found here.
The PEAQ method was developed for pure alfalfa stands. Using this method to determine %NDF of alfalfa-grass mixtures will be inaccurate. However, this method can still be beneficial to estimate the %NDF in the alfalfa portion of the field. Grasses continue to follow harvest estimations based on growth stage.
Most of the Alfalfa in the state had reached at least 17 inches, which would have a %NDF of 29.2 in the late vegetative stage. In some areas, though, alfalfa has reached the 10% bloom growth stage. Alfalfa, which is 19 inches tall and in bloom, is projected to have an NDF of 33.4.