Due to the maturity of most fields in our area, this will be our last week of measuring alfalfa heights this year. Most of our remaining fields will be at peak quality by the middle of next week, and only pure alfalfa stands at high elevations are more than 10-12 days from peak maturity. In order to bring you timely forage quality updates, this edition will focus solely on alfalfa height monitoring. Check your fields because peak quality may be now!

Alfalfa height is a reliable indicator of NDF values in the field, so we use alfalfa height to predict Neutral Detergent Fiber (NDF) for alfalfa, mixed alfalfa/grass, and pure grass stands. When using alfalfa and grass height as an indicator of NDF content, in general:

Begin cutting 100% grass stands when nearby alfalfa is 14" tall to achieve the desired 50% NDF.
Begin cutting 50/50 alfalfa/grass stands when nearby alfalfa is 22" tall for the desired 44% NDF.
Begin cutting 100% alfalfa stands when alfalfa is 28" tall for the desired 40% NDF.

To achieve the desired NDF it is necessary to begin cutting at NDF values slightly lower than the desired value assuming some harvest and storage losses (which the above alfalfa height values reflect). For example 28 inch tall alfalfa is closer to 38% NDF but you will need to start then to end up at 40% NDF. Predicted  days to cut are based on daily NDF increases for grasses (1%), 50/50 mixed stands of (0.8%), and alfalfa (0.5%). Typically, NDF increases about 0.8 to 1.2/day for grasses and 0.4 to 0.7/day in alfalfa, expecting the lower end of that range in cooler weather and the higher end in warm. See the attached fact sheet for more details: Predicting Spring Fiber Content of Forages. 

Always check your fields to verify your heights and conditions!

*We were unable to measure these two fields this week, so this value is an estimate (+/- 1.5") based on last week's measurement and the relative growth of other fields nearby.