First Cutting Monitoring – May 19th, 2020 SCNY Report

alfalfa at 16"

This is the SCNY Team’s second full week of monitoring alfalfa heights for first cutting quality in 2020. A full report for the six-county region can be found in the following link: Alfalfa Height Reporting Sheet 5.19.2020.

Team Agronomist, Janice Degni, shares observations from the field this week:

This week alfalfa growth has separated by soil conditions. Usually most fields are within a narrow zone of a few inches of height differences. What I observed this week is that the alfalfa on heavier soils in conjunction with cooler temperatures are continuing to grow very slowly. Their growth doubled over last weeks with up to 3″ of increased height but still lag behind fields that jumped as much as 7″ this week.

alfalfa height

alfalfa vs grass

It’s time to get around and take a close look at your fields.  The trigger for harvest of grass stands is 15″ alfalfa and plenty of fields are at or above that height. I have seen a few heads of orchardgrass poking out. Other grasses are still in the pre-boot stage but that could change quickly with the warm days in the forecast. Its very important to assess your stands that are 50:50 alfalfa and grass or less alfalfa. The window to capture peak quality is quickly approaching.

You may find that the alfalfa is smaller than you would like and yields will be lower than normal. The question becomes do you want plenty of a low quality feed or a lower yield of high quality feed?

The lost yield can be made up in the 2nd cut if we have plenty of soil moisture and the field get a shot of nitrogen (75-125 lbs actual N) either from fertilizer or manure to boost the grass yield in the next cutting.

The following graphs from data Dr. Jerry Cherney collected a few years ago show the potential for a regular decline in NDF digestibility as the grass matures.  Higher temperatures will sharpen the decline.

NDF Digestibility Delcline graph

If you want to double check the conditions in your fields you can collect a scissors cut sample and send to the lab for analysis. Dairy One can send back results in 24 hrs, usually. Then you will have hard numbers to guide your decision on your strategy for harvest.

During our Tuesday effort to collect measurements, there were plenty of triticale fields being mowed and efforts from several farms were being made to start harvest of pure stands of grass this week.

This year, the range of temperatures and soil conditions has varied greatly – it is imperative to look at your own fields this week to make your determination on when to mow! Mixed stands of grass and alfalfa will be soon to follow – many fields we monitor have less alfalfa than anticipated, so harvesting earlier will lead to a more favorable NDF content in those situations.

Cornell’s Climate Smart Farming tool ( can be utilized to determine GDD by location. For grass determination, I selected base 32, and inputted several locations across our region. Most locations will hit that targeted 900 GDD(B32) for prime grass quality this week. See the locations below for the targeted GDD accumulation or visit the Climate Smart Farming Website to plug in your location.

GDD b32 gdd b32 _2


As a reminder, for prediction of NDF content, the height of alfalfa as an indicator is as follows:

  • 100% grass stands – cut when nearby alfalfa is 14 inches tall (achieves 50% NDF)
  • 50/50 grass/alfalfa stands – cut when nearby alfalfa is 22 inches tall (achieves 44% NDF)
  • 100% alfalfa stands – cut when alfalfa is 28 inches tall (achieve 40% NDF)

Alfalfa height at optimum mixed stand NDF

From Kevin Ganoe, the CNY Dairy, Livestock & Field Crops Team’s Forage Specialist:

Predicted days to cut are based on daily NDF increases for grasses of 1.0% point, 50/50 mixed alfalfa/grass stands of 0.8% points, and alfalfa of 0.5% points and are adjusted for the coming week’s weather. Typically NDF increases about 0.8 to 1.2 per day for grasses, with cooler weather being the lower end of the range and warmer weather being the higher end. For alfalfa, NDF increases about 0.4 to 0.7 per day, also dependent upon warm/cool weather.

Look for our next report of monitoring heights to come out on Wednesday, May 27th.  In the meanwhile, if you can’t get out to check your fields, call one of us on the team.  We’ll be glad to help out.

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