As we look back over the years, there has been no lack of information on when is the optimum time to cut alfalfa during the course of a growing season. Some of the proposed methods have been as follows:
With all of the above guidelines as options, it becomes confusing as to what is the best strategy for determining optimum cutting time throughout the course of a growing season. To make matters even more complicated, using any of these guidelines as the sole criteria for making a cutting management decision is probably going to lead to a wrong decision in a significant number of situations. For example, Figure 1 shows the relative feed value (RFV) of fresh-cut alfalfa on a given date for each of the past six years. Using June 1 as a target date to start harvesting "dairy quality" forage, a producer would have been too late in 1991 and 1992, about right in 1993, 1994, and 1995, and too early in 1996. Additionally, if RFV's are plotted against visual maturity stage, we would see a similar spread in quality at any given maturity stage (data not shown).
We have long known that making accurate estimates of harvested (bales or haylage) forage quality is an impossible task. Why then should we assume that estimating the quality of standing alfalfa is any easier? A primary reason why no single criteria can predict optimum cutting time is that environment plays a key role in both alfalfa growth and forage quality. Moisture stress and/or cool temperatures result in a slower decline of forage quality and generally slower growth whereas high temperatures result in a more rapid decline in digestibility and increased growth when adequate moisture is present. Keeping these relationships in mind will help in making forage quality estimates, however, there is still more to consider.
Until plant breeders develop the perfect alfalfa plant, there will always be tradeoffs between yield (Y), quality (Q), and persistence (P). For most dairy producers, forage quality is a non-negotiable item. In other words, it is typically the driver of the cutting schedule. The pertinent question then becomes: How do I harvest alfalfa of acceptable quality without giving up a significant amount of yield and little, if any, persistence? Or perhaps a follow-up question, CAN IT BE DONE?
Assuming that stand persistence is a primary goal (and why shouldn't it be?), let's establish two ground rules. First, routine harvesting of alfalfa four times before September 1st is not an option. Both research and producer experience point to this system as one that quickly translates to rapid stand deterioration with very little gain in quality. In reality, Mother Nature rarely allows this option in east-central Wisconsin anyway. Second rule, no cutting during the "critical fall period" (roughly September 1 to October 15).
First cut: The optimum time to harvest the initial spring cutting of alfalfa is determined by knowing two factors: 1) the number of rain-free days it will take to harvest and 2) the quality of the standing forage. The first factor will help estimate a baseline starting point in terms of forage quality to allow for the harvest to be completed before quality parameters drop to an unacceptable level. In many situations, this will mean starting to cut when standing forage RFV is in the 170 to 180 range. For all practical purposes, forget about visual stage of maturity and calendar date. Neither factor, in and of itself, makes milk. The tools are now available through local scissor-cutting results and your own field estimates using Predictive Equations for Alfalfa Quality (PEAQ) to make close enough estimations of standing forage quality that quality "train wrecks" can be avoided assuming the weather cooperates. The first-cutting of alfalfa offers the most opportunity for economic loss or gain and for this reason gross miscalculations of forage quality simply have to be avoided.
Second and third cut: The rate of forage quality decline for summer cuttings is slower than that of first-cut. Because there is less volume, the crop can be made in a shorter period of time. For these reasons, the harvest window is typically wider but keep in mind that environmental factors are still important and can significantly impact forage quality. Calendar date and visual maturity are more useful factors in gauging an optimum cutting time for the summer harvests. Another consideration in cutting the second and third crop alfalfa is that you want to be done by about August 20 to 25. By doing so, the alfalfa canopy has time to develop before dandelions make their autumn comeback. In most years this will translate to no more than a 35 to 40 day cutting interval. Typically, the longest cutting interval is between the 2nd and 3rd cut when soil moisture is most limiting.
A late fall fourth cut: As we've said many times before, the decision to make a late fall fourth cutting needs to based on forage need. Up until this point, little or nothing has been sacrificed in terms of stand persistence. The late fall cut, even after a killing frost, now puts the stand at additional risk. At the very least, some reduction in first-cut yield will occur in the subsequent year. However, that might be a good risk to take if forage inventories are low and prices are high for good quality forage.
When discussing forage quality and cutting schedules, the topic of variety differences is always an issue. There are clearly some varieties that have been developed for improved forage quality. However, making major deviations in cutting schedule strategies based on variety alone should be done with caution and only when you are certain a particular variety is significantly ahead or behind others in terms of forage quality. Variety may be a factor in determining those fields that are harvested first.
There is no simple alfalfa cutting schedule recipe or rule of thumb that will apply every year or for every farm. However, for an alfalfa enterprise to be profitable, producers must optimize forage yield, quality, and stand persistence. Estimating first cut forage quality before the crop is actually harvested is now possible with the availability of scissor cut results on an area basis and making PEAQ estimates on an on-farm basis. Use these tools to make first cut harvest decisions. Summer cuts will typically be made at 35 to 40 day intervals unless environmental factors deviate significantly from normal. Plan to be out of alfalfa fields by about August 25th and make late fall cutting decisions based upon forage need under the realization that stand persistence and subsequent plant vigor will be put at riskFor more information contact Mike Rankin