By Alberta Agriculture and Forestry
Aug. 31, 2015 - An Alberta Agriculture and Forestry specialist warns that cutting alfalfa now increases the risk of winterkill.
"You should wait until there a couple of light frosts on the crop, or roughly September 15, before doing the second cut on an alfalfa or an alfalfa grass mixed hay crop," says Barry Yaremcio, beef/forage specialist, Alberta Ag-Info Centre, Stettler. "The alfalfa plant wants to grow and produce seed. If you cut it now, it will want to regenerate and develop a seed set before it freezes. With only 20-30 frost-free days left, it won't be enough time for it to recover from the cutting to ensure winter survival."
An alfalfa crop needs about 45 days to recover from being cut. "During those 45 days the growth on the alfalfa plant, once it reaches that 12-14 inches in height, is where it starts putting food back into the root system to make it through the winter. If the plant only gets 6-8 inches tall before going dormant, all it is doing is taking the root reserves out of the plant leaving nothing to get it through the winter."
Yaremcio says that even if there is a light frost before cutting occurs, there will not be nitrate accumulations. "Alfalfa and the legumes are different from annual cereal crops. In legume root systems there are nodules that will horde nitrogen, only releasing what is needed for daily use. Typically, alfalfa and other hay crops also don't get the same level of fertilization as would an oat or barley crop, meaning the residual nitrogen in the soil is less which also helps reduce the risk."
Yaremcio says the quality loss incurred by waiting to cut the crop in the fall is less now that it would have been earlier in the year.
"As the sunlight hours decrease, the plants slow down and start going into their dormant phase. As such, even if you wait another two to three weeks to cut, the quality drop is much less than you would get in June-July."