Several research studies have found that cutting alfalfa late in the afternoon results in the best forage quality, notes Ev Thomas, vice president of the W.H. Miner Institute in Chazy, N.Y. That's because alfalfa plants produce sugars and starches during the day and lose them at night.

However, most of these studies looked at alfalfa which was harvested for dry hay, not for silage. Thus, researchers at the Miner Institute decided to harvest alfalfa for silage using the "a.m vs. p.m." technique. They found no difference in sugars, starches, neutral detergent fiber or in vitro digestibility between the alfalfa cut in the morning and that cut in the afternoon. However, they did notice the following trends:

  • Alfalfa that was cut between 3 and 4 p.m. was slightly higher in sugar and starches than alfalfa cut between 7 and 8 a.m. However, these differences either decreased or disappeared entirely by the time the forage reached 40 percent dry matter.
  • Alfalfa that was cut in the morning was ready for ensiling in about 9 hours, while the alfalfa cut in the late afternoon wasn't ready until after lunch the following day. However, this extended length of time in the field did not appear to have detrimental effects on silage quality.
  • There was no significant difference between a.m. and p.m. cutting after the forage fermented in mini-silos.