alfalfa – Champlain Valley Crop, Soil & Pasture

Consider the Density and Vigor of Your Cover Crop

UVM Ext. Agronomy Outreach Professional

Over the past year there has been growing interest in the farming community in trying to no-till alfalfa hay seedings into winter cover crops as a way of reducing erosion and saving time and fuel. Come spring, there will be a number of farmers who want to plant then or early summer who will look at their fields wondering “should I plant now, or wait until later?” While we have not yet done any formal research looking at alfalfa establishment under different management systems and the associated economics, there are some clues that may be able to guide us until we have more data.

One clue we can look at when deciding whether to plant in early spring or early summer is cover crop stand density. (Late-summer seeding is also a consideration that we won’t discuss in this article.) We know from helping farmers no-till-renovate pastures/hay fields that a productive and competitive hay field will outcompete your no-till seedlings for light and nutrients. We should expect this same thing to happen when we have cover crops.

A field was planted to winter rye after corn silage harvest in early September; by December it completely covered the soil surface and was between 4 and 6 inches high.

severy-pic-1-cropped — Dense cover crops like this winter rye can be good for soil conservation, but challenging for no-till planting.

This success was due in part to early planting, full seeding rate, and timely rain. In spring, we expect that this crop is going to take-off and, with proper management, will be very high yielding. If alfalfa mix were planted into this stand in April without any control methods, will our seedlings be able to compete? Maybe, but we wouldn’t count on it. We are not suggesting that a productive stand is bad, as it provides many environmental and economics benefits, but it must be managed correctly. So, in this situation, we would recommend that before seeding an alfalfa mix, a farmer should either terminate the cover crop, or wait until mid-May and harvest for livestock feed before seeding. If the field is terminated in April, the alfalfa should be planted with a nurse crop like barley or oats. If properly killed, the winter rye will be barely noticeable after about a month. If there is no nurse crop, there will be a substantial amount of bare ground which will be susceptible to erosion and weed pressure.

Another field was planted in late September 2015 to winter rye after corn silage harvest. By early April 2016, although the cover crop did protect against erosion, there was still a lot of bare soil.

severy-pic-2-cropped — In contrast to the first picture, a winter rye crop that was lower yielding will be less competition for a no-till crop like alfalfa.

A crop like this can produce high quality livestock feed, but will be very low yielding. In this type of situation, the farmer can go ahead and plant alfalfa mix. S/he can terminate the cover crop beforehand, but there should be enough open canopy that the cover crop should not be a problem. This winter rye can later be mowed for livestock feed, or possibly even left and combined for seed for next fall’s cover crop.

Do you have questions about this work or would like assistance with no-till alfalfa? Contact Nate [802-388-4969 ext. 348, nathaniel.severy@uvm.edu]

By Nate Severy, Agronomy Outreach Professional

This year there were a number of farmers who no-tilled alfalfa in clay and silty soils throughout Addison County. While this was a difficult year for good alfalfa establishment due to our dry, hot weather, all of the no-till alfalfa farmers had successful stands.

Below is a summary of what these farmers did that contributed to their success:

All farms planted during a “window of opportunity”. While all farms managed their fields differently, there are generally 3 times through the year where there is a “window of opportunity” in which you can successfully plant alfalfa into your cover crop. These are: early April before green-up, mid-late May immediately after harvesting your cover crop for forage, or August after you combine and harvest grain and straw. One positive aspect about no-till seeding is that in the spring only the top inch of soil needs to be dry in order to plant, as opposed to the entire plow layer with conventional field prep. This means you can seed much earlier in the spring without the risk of turning your clay soil into moon rocks.

All farms fertilized, prepared good/level seedbeds, and planted a cover crop last fall after short-season corn silage. Cover crop planting dates ranged from early September to the beginning of October. If you are planning on harvesting your winter rye/triticale/wheat as forage, the earlier you can plant in September, the better your spring yield will be. That means you will want to make sure you plant a corn silage variety that can be harvested early enough that you have adequate time to prepare a proper seedbed. If you do not want to harvest forage from the cover crop, either plant at a lighter rate or plant a mix that has a winter cereal with a winter-kill crop like oats or radishes.

All farms planted at the proper seeding depth. For winter cereal grains, planting depth should be between 1-1 ½ inches, which means you need to plant with a grain drill. Broadcasting and lightly tilling it (followed by a roller) can work, but there is a very fine line between incorporating your seed and burying it. Broadcasting and only going over the field with rollers is not recommended. The seeding depth for alfalfa should be between ¼ to ½ an inch. Most farms used a grain drill, but it is possible to broadcast your seed if you “aggressively scratch” the field before seeding and pack it several times afterwards.

All farms planted alfalfa into a low-competition environment. Some farms planted into their cover crops in mid-April before there was much spring growth, a farmer planted his alfalfa in May after harvesting the cover crop as forage, and a few farms planted alfalfa in April, spraying and killing their cover crop immediately afterwards. You can have good alfalfa establishment in a thick cover crop/nurse crop, but you will have less first-year alfalfa yield when compared to a light cover crop/nurse crop.

Three farms successfully frost seeded 5lb/ac red clover in March into their cover crops. Frost seeding can be an effective way to introduce crops into fields. However, you need three things to happen perfectly: very small seeds, soil that will freeze-thaw, and bare ground. These cover crop fields seemed to be good candidates for frost seeding 5lb/ac red clover in March, and by August you could definitely see where we did and did not frost seed.

Planting alfalfa and other hay crops is risky no matter the year. Hopefully more farms try this method of seeding so we can learn more about the best way to establish and maintain this valuable crop.

No-till alfalfa being planted into a cover crop and corn residue

Do you have questions about this work or would like assistance with no-till alfalfa? Contact Nate [802-388-4969 ext. 348, nathaniel.severy@uvm.edu]