Alfalfa fields: Be prepared for 2018
This year, I am getting a lot of reports of winter injury and winterkill in alfalfa stands throughout Montana. Following a disastrous year in 2017, where many were left short in their hay stacks and had to buy hay, this can create further issues moving into 2018. Already, I have been in several fields where it looks like the first harvest is going to be set back due to winter injury, and several pictures have crossed my desk of patchy fields that have significantly decreased or absent spring growth.
So how can you tell if your alfalfa has experienced winter injury? If it looks like you have areas where plants are stunted and growing slowly, this is a good first sign. Also, evaluate the crowns of the plants. If there is only new growth coming on one side of the crown or the growth is asymmetrical, this is a good indicator of winter injury. I am a big proponent of digging up a couple of plants in the spring to see what is going on underground. Look for overall health of the taproot. If you notice that there appears to be discoloration near the crown, this too can be an indicator of winter injury.
Also look at stem and plant density. I prefer to evaluate stem density because it can be hard to tell if you are looking at one plant or two sometimes when evaluating plant density. If you have over 40 stems per square foot, you are probably doing OK. In younger stands, the closer we are to 50 to 55 stems per square foot, the better. If you are under that 40 stems per square foot mark, then you should consider renovating, or interseeding with a different forage species. It is easiest to do stem counts when the growth is small, around three inches, and before they get too tall and become intertwined.
If you do suspect that your field has experienced winter injury, there is some good news. Most often, only the first harvest is going to be severely affected. Generally, if growing conditions are good later in the spring and summer, the regrowth will be adequate and you can get close to normal in your later harvests.
The bad news is if you have significant winter kill where plants just simply did not survive. This winter had a lot of ice sheeting, and the spring has had flooding in many areas. Alfalfa cannot survive long periods of time where there is no gaseous exchange due to ice sheeting. If it's underwater too long, it can "drown" the plants out, or at the very least, expose it to secondary bacterial or fungal diseases.
It is important to assess your fields in the spring to figure out a plan for the coming year. If your alfalfa field experienced significant winterkill and is less than a year old, you do have the opportunity to interseed or start over with new alfalfa. However, if your stand is more than a year old, autotoxicity will be too big of a risk, and interseeding or replanting alfalfa is not recommended.
A good idea in this instance may be to look to an annual forage. Research has shown that on a tonnage basis, you will generally harvest more tons per acre with an annual forage compared to a perennial, even alfalfa. This will help to put more hay in your yard for the coming winter. And with many of our new annual forage cultivars, we are still able to harvest high quality forage for our animals to consume.
Overall, it is important to get out and scout your fields as soon as you can. Evaluate if there is any damage, then start planning for the coming year. Many are going to be planting late due to the large amounts of spring moisture, but we still have many options to consider if you do have to pull out your alfalfa. And as always, if you have any questions, talk to your local Extension agent, NRCS consultant, agronomist or Extension Forage Specialist.