Read the current Progressive Forage digital edition

Let’s talk about why your alfalfa didn’t test well

Dan Undersander for Progressive Forage Published on 14 November 2016
Green chopping

How was the quality of the alfalfa you harvested this year? Weather often has a large impact. However, harvest management can have a huge effect on drying rate and quality of harvested forage. Now is the time to evaluate how this year went and to plan for what changes might be implemented next year.

We should consider that leaves have a relative forage quality (RFQ) of about 550, while stems have an RFQ of 70 to 80. Thus, if we want quality forage, we must focus on harvesting leaves.

Figure 1, from a study of four rake types in three states, shows the effect of leaf percentage on RFQ of the harvested forage. Leaf percentage accounted for 71 percent of variation in forage quality.

Effect of leaf percentage on RFQ

If the alfalfa is growing well, we should expect about 45 to 50 percent leaves when harvested at the bud stage. This shows up in Figure 2, when interns in a Land O’Lakes by Winfield program monitored some fields through harvesting.

Change in leaf percentage through harvest

The fields averaged about 45 percent leaves in the standing alfalfa before cutting; the leaf percentage fell slightly through mowing and conditioning (about 2 percent) and then fell dramatically in the harvesting process (about 13 percent).

These were fields harvested for haylage where we would expect fewer losses than when alfalfa is harvested for hay. The chopping for haylage harvesting resulted in an average loss of about 40 points RFQ due to leaf loss.

What can be done to minimize leaf loss? Consider the following:

Evaluate alfalfa stands

Did you start with 45 percent or more leaves, or did many fall to the ground prior to mowing? If the latter was true, then consider – especially under cool, wet conditions – that an application of fungicide at early regrowth stages may be beneficial. Evaluate carefully, as fungicide is an expense that can be beneficial but may not always be needed.

Check after mowing and conditioning

Generally, we have seen small leaf loss at this stage, but the following should be kept in mind:

  • A flail/impeller conditioner will result in increased leaf loss of alfalfa compared to a roller conditioner.

  • A wide swath will enhance drying rate and reduce non-fibrous carbohydrate loss. Non-fibrous carbohydrate is 100 percent digestible to animals. The loss also results in a drop of RFQ.

    Putting cut alfalfa into a wide swath will also mean the yield of the next cutting is increased because the field is driven for harvesting sooner so, with less regrowth and if the crop is to be irrigated, that can begin sooner.

For larger operations, we are recommending triple mowers rather than self-propelled because the latter only make swaths that will fit between the wheels. The yield loss from respiration during drying, and from next cutting due to delayed irrigation, can be significant.

Consider that every time you move forage prior to harvest results in a leaf loss

Wetter forage results in less leaf loss when moved. So rake or merge above 40 percent moisture if possible. Each operation – e.g., tedding, windrow inverting – prior to harvest results in leaf loss.

Rolling forage across the ground results in leaf loss. Move forage to the middle with a large rake rather than to one side to reduce moved distance and rolling of the hay. Mergers result in less leaf loss than rakes since they pick up the forage and move it on a conveyer belt.

Thus, a recommended procedure would be to mow, rake or merge when at 40 to 50 percent moisture and harvest. In the Midwest and Northeast, haylage made with wide swaths can often be harvested the same day it is cut. In the West, hay can be harvested in two to three days rather than five to seven.

Minimize leaf loss during harvest

If the windrow is a size that is near capacity of the baler or chopper, then harvesting is more efficient in terms of fuel and labor. The larger windrow also results in less leaf loss at the harvester (either baler or chopper) pickup during harvest. Also look behind the harvester: Is there a layer of leaves falling on the ground behind the bale chute?

What is falling between the belts of a round baler? Is there a green cloud around the chopper wagon or truck? Each of these are signs of leaf losses that result in reduced harvested forage quality.

Leaf loss cannot be eliminated; it can, however, be minimized. By being sensitive to the concept of “harvesting leaves” rather than “harvesting hay,” one can observe where leaf loss is occurring in your operation and take steps to reduce losses. In some cases, different machinery may be called for, but in most cases, equipment adjustment and timing of use may make significant differences.  end mark

PHOTO: Green chopping. Photo by Staff.

Dan Undersander
  • Dan Undersander

  • Forage Agronomist
  • University of Wisconsin
  • Email Dan Undersander

Before commenting on our articles, please note our Terms for Commenting.