By Mark Sulc
The long-standing recommendation has been to take the last harvest of alfalfa by early September in northern Ohio and mid-September in southern Ohio. Every year I observe that many people do not follow this recommendation, probably for various reasons. Most people taking only three cuttings are finished with the final harvest by early to mid-September. But the fourth cutting is another story. As of the end of last week, only about half of the fourth cutting of alfalfa in Ohio was complete, which reflects the rate of fourth harvest completion going back at least five years.
I have heard some say that the fall rest period is not necessary and fall cutting never harms their stands. This could well be the case in many years on many farms, especially where excellent management is in place…where a good variety is used under excellent fertility and high soil pH, on well-drained soils, etc. Our killing frosts for alfalfa are also later than they used to be, and this fall is predicted to be warmer than normal. So I am not going to disagree with people about their fall cutting practices. But my question for those who take fall cuttings is: are you certain that it is not harming your stand productivity at all? Have you made a side-by-side comparison to see if there is a difference? If not, then try it this year. Leave some strips that you don’t cut when you take a fall cutting this year, mark those spots and look at them carefully next spring compared with where you did cut in the fall.
Cutting is always a stress to the plant. The recommendation to give plenty of time for recovery before winter is still a sound and very safe recommendation, particularly on soils that have less than ideal drainage or where the alfalfa is stressed.
There are situations when taking some risk may give a reward. The beautiful high quality fall forage present in an alfalfa field in late September to early October may be valuable enough to take some risk with cutting it at that time. The weather through the rest of the fall and winter may cooperate nicely and it could be no problem. But be aware there is more risk with cutting late, and the risk probably increases in the latter half of September and into early October because the recovery time for replenishing energy reserves used in regrowth soon after cutting is growing shorter with each passing day.
A number of factors affect the level of risk incurred with cutting during the fall period. These include overall stand health, variety disease resistance, insect stress on the stand during the summer, age of stand, cutting management, fertility, and soil drainage.
A vigorous, healthy stand is more tolerant of fall cutting than a stressed and weakened stand.
Alfalfa varieties with high disease resistance and good levels of winter hardiness will be more tolerant of a fall cutting. Adequate fertility, especially soil potassium levels, and a soil pH near 6.8 will improve plant health and increase tolerance to fall cutting. Stands under 3 years of age are more tolerant of fall cuttings than older stands where root and crown diseases are setting in.
The cutting frequency during the growing season can affect the energy status of the plant going into the fall. Frequent cutting (30 day intervals or less) results in the plant never reaching full energy reserve status during the growing season. This makes the critical fall rest period more necessary for plants to accumulate adequate reserves before winter. So a fifth cutting taken in the fall carries more risk than taking a fourth or third cutting during the fall.
A final factor is soil drainage. Alfalfa stands on well-drained soils tolerate later fall cuttings better than alfalfa on moderately or poorly drained soils. Low plant cover going into the winter from late cutting increases the risk of winter heaving on many Ohio soils. We have observed significant heaving in the past in NE Ohio, and many of those stands had been harvested the previous fall.
Cutting alfalfa during the critical fall period is always tempting due to the high quality of the forage in the fall and the sunny fall conditions. Carefully consider the condition of the stand and the risk factors discussed above before taking a fall cut. We will be taking a fourth cutting in one experiment around September 21-23, right beside where a fourth cutting was taken September 9th. So next year we will closely look at the spring yield following those two fall harvest dates. Join us with your own side-by-side comparison.
Source:osu.edu