Here are numbers that are helpful when using alfalfa and grass height as an indicator of NDF content:

In general we say 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.

This second week of monitoring shows that all grass fields should have been cut by now. It may even be time to consider letting some grass fields go to harvest later for a lower quality feed where you see predictions for over 55% NDF. Most 50/50 mixed stands should be cut now or cut within the next few days. A number of pure alfalfa stands are at 28 inches and ready to cut. The need remains for you to look for fields close to your farm in the enclosed table and to also measure your own alfalfa to make good management decisions. Some fields to the west of our region and at elevation are now only ready to cut grass so there is a wide variation in cutting dates. Know your conditions!

Next and last report for 2015 will be on May 26!