The bottom line is this: We are on course this year to reach 40% NDF in the alfalfa crop at an unusually early calendar date. Thus, it is even more critical for dairy producers to follow the GDD accumulation at a weather station as near as possible to their farm to time this year’s first cutting at an optimal date. The Michigan State University Agricultural Weather Office maintains a website that allows you to track GDD accumulations at nearby weather stations. Go to the website and click on “Enviro-Weather.” This will bring up a map of Michigan showing the weather stations recording this important data. Click on the weather station closest to your farm, then under the heading “Degree-day tools” go to “Degree Day accumulations for Region (alfalfa and corn development).” This will bring up a table of GDD accumulations. The correct GDD accumulation data for alfalfa is in the second column from the left with the heading “Degree Day Base 41oF for Alfalfa.”
It is impossible to forecast exactly what weather we will experience between now and time for first cutting. However, if the weather this winter and so far this spring is any indication it will be extremely important to follow alfalfa GDD accumulations very closely to optimally time this year’s potentially early first harvest.
1GDD equals growing degree days calculated using base 41 method
2Growing degree day accumulation as of 3/25/12
3Years include 2007, 2008, 2009, 2011
4No data in 2007 or 2008 for Richville/Frankenmuth station
Source: Craig Thomas, Michigan State University Extension