From Cornell University Cooperative Extension
This is our second week of monitoring first cutting for quality in 2013. 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 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.
For New York dealers and customers:
Since last week alfalfa height has increased as much as 4-6 inches. As you can see at many locations pure grass stands should already be harvested and mixed stands should be cut before next Tuesday. Although there was frost on Tuesday morning and alfalfa and grasses werebent over from the cold we did not observe much if any frost damage. Most stands seemed to recover as the day warmed up without any permanent wilting.