If you are not familiar with our procedures we use alfalfa height to predict Neutral Detergent Fiber (NDF) for alfalfa, alfalfa/grass mixed and grass stands. Alfalfa height has proven to be a reliable indicator of NDF values in the field.

Here are numbers that are helpful when using alfalfa and grass height as an indicator of NDF content. In general:
Begin cutting 100% grass stands should be cut when nearby alfalfa is 14 inches tall to achieve the desired 50% NDF.
Begin cutting 50/50 mixed alfalfa and grass stands when nearby alfalfa is 22 inches tall for the desired 44% NDF.
Begin cutting 100% alfalfa stands when alfalfa is 28 inches tall for the desired 40% NDF.

The desired NDF for all grass fields is 50%, 50/50 mixed alfalfa and grass fields is 44%, and pure alfalfa stands is 40%. Predicted days to cut are based on daily NDF increases for grasses of 1% point, 50/50 mixed stands of .8% points and alfalfa of .5% point. Typically, NDF increases about 0.8 to 1.2/day for grasses expecting the lower end of that range in cooler weather and the higher end in warm. Alfalfa NDF increases about 0.4 to 0.7/day again figuring the lower end of that range with cool temperatures and the higher in warm. Predictions are adjusted for the coming week's weather and right now we are assuming normal growth.

In the attached tables locations around the region are listed where we have measured alfalfa height. You can use the location and elevation as a guide to conditions that may be similar to your own. Always check your fields to verify your heights and conditions!

On average the alfalfa height increase slowed this week with an average height of 15 inches an increase of only 3 inches. Although growth has slowed with the cold damp weather that same weather doesn't allow for catching up on any field work. As we suggested last week if weather becomes more favorable remember to prioritize harvesting those fields left that are that still dairy quality. This may be a year of cutting first and planting corn second, having separate crews working on both and or having some custom work done.

We would expect all but two locations would have 100 percent grass stands ready to harvest by next week. Remember with all grass stands once you hit 50% NDF you have about 4-5 days to cut as NDF is accumulating at a rate of 1 percentage point a day. Our predictions would indicate 48 percent of the 50/50 mixed stands could be ready by or on our next cutting date, May 21. There may be several locations where pure alfalfa stands should be at a height to be cut by then.