1. Field Observations

I don't have to tell anyone reading this that the past 2-3 days have felt like a week - lots of tractors in fields doing all sorts of things - spreading manure, tilling, chopping, spraying, planting…. Hopefully you've felt like you've made some progress in what has been a difficult, wet start to the month.

I will keep this update brief - (a) I've found my first few black cutworms in pheromone traps around the region, and (b) here are the alfalfa heights and growing degree days:

2. First Cutting Forage Quality

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 following fact sheet for more details: Predicting Spring Fiber Content of Forages.

Always check your fields to verify your heights and conditions! Remember that these predicted harvest dates are not set in stone, and will fluctuate as we go along. And they may creep up on us - especially since the fields are getting a lot of moisture now, and the temperature is only going up!

Locations and heights AS OF May 12, 2025:

If your location is not listed by the know the height of your alfalfa, this chart is for you.  As of MAY 12, 2025:

3. Growing Degree Days (GDD) (See: Climate Smart Farming Growing Degree Day Calculator)

Growing degree days (GDD) are calculated by taking the average daily temperature and subtracting the base temperature for development of a given organism ((High + Low)/2 - base temp = GDD). For corn silage, we are using base 50/86, as corn development starts at 50 degrees F and ceases above 86. Check your location and planting date (more planting dates to come):

See you in the field!