We have been working with cover crops on our farm since the fall of 2012. Choosing what covers to use is an important step in managing them, and there are several parameters to look at to choose the best cover crop for a given situation.
What is the cover’s purpose?
Not all cover crops are created equal. Some are better at certain tasks than others. Grasses are great for erosion control and building soil structure, but they can tie up nitrogen in the spring, which needs to be considered. Nitrogen fixers like clover and hairy vetch can help feed N to next year’s corn crop, but they can be tough to establish early enough to get good growth to ensure they survive winter and grow enough in spring to see any benefit from N fixation. If livestock are going to be grazing the cover their nutritional needs should be considered.
What is the following crop?
The cash crop planted into a cover crop can determine what cover or mix of covers is best to seed. Our go-to ahead of planting soybeans is cereal rye for a number of reasons. Cereal rye is pretty hardy, and can be seeded later than many other covers. We broadcast 50 pounds of rye after corn harvest. We have done this as late as mid-November with good results. Cereal rye will put on a lot of biomass if allowed to grow well into spring. We are at a point now where we are comfortable letting it grow right up until planting depending on field conditions and forecasted weather. Most of the time our rye is headed out, but not pollinated when we terminate it. Allowing the rye to grow a little longer and planting into it “green” has cut a post emerge herbicide pass out of our soybean program in those fields. The mat of dead rye left behind acts as a weed barrier. Our soybeans planted after cereal rye will see their first and only post emerge herbicide in mid to late July. The rest of our soybeans are likely to have seen their second application by that time. Cereal rye ahead of soybeans is kind of a no-brainer, and it’s relatively easy to manage.
Going to corn we look to cover crop mixes. So far, we have kept it pretty simple with either a mix of annual ryegrass, tillage radish, and clover, or oats and radish with or with the clover. Oats and annual ryegrass can sequester nutrients and put down good roots to build soil structure. The advantage of ryegrass is it will overwinter and continue to grow in spring. Oats on the other hand will die in freezing weather as will the radishes. Winter kill makes for easy termination of a cover, but there won’t be any spring growth. I tend to like oats over annual ryegrass mostly because we have had better luck getting oats established and growing. In our experience oats get a better stand when seeded by airplane. We see our cover crops in fields going to corn before the current year’s soybean harvest begins. I would like to be able to get the soybeans off early and drill and broadcast these covers for better establishment, but so far we haven’t been able to get soybeans off the fields as early as we would like to leave enough warm weather to get sufficient growth before winter sets in. This spring we intended to plant soybeans early in some fields to accomplish this, but wet weather pushed planting into May and early June.
Herbicides used in cash crops can affect cover crop establishment. We have to pay attention to what we are spraying in our corn and beans. There are herbicides with a long enough residual period than they may kill a sprouting cover crop in the fall.
Another consideration is if we are using a herbicide to terminate the covers in spring is there may be a wait period for cash crop planting. For example, if we used 2,4-D mixed with glyphosate to maybe kill off some marestail in cereal rye we need to wait a week to plant soybeans so that 2,4-D won’t have adverse effects.
Sharing the cost
Our 3 year contract just expired, but we have had our cover crop acreage enrolled in the NRCS’ Environmental Quality Incentives Program. EQIP provides funding to plant cover crops, and to be honest that funding pretty much covered our seed cost for those three years. If we renew the contract it has to cover different acres so if we expand cover crop acreage, we won’t have cost sharing on all of it like we have so far. A downside of the EQIP acres is we can’t double dip and get funding and profit at the same time. Essentially this means we cannot keep wheat in the rotation on those fields. Now that our contract is up, we can put wheat back out on those acres.
The return on investment with cover crops can be tricky to figure. With cereal rye we are pretty confident we are getting back at least half the cost of putting out the rye by eliminating a herbicide pass the next summer. Cereal rye is relatively cheap, too. We can get it on and seeded for $18-$20 per acre. Cover crop mixes can easily go upwards of $40 per acre. The long-term benefits are hard to put a dollar amount on. I’m sure we are stopping erosion, and I see better soil structure developing with cover crops. All the extra plant material we are raising between cash crops surely has benefits like scavenging and keeping plant nutrients that might otherwise be lost over the winter. We also get weed control from the winter kill covers. We are also putting additional organic matter back in the soil which should improve water holding and nutrient capacity. But these things are admittedly hard to put a finite number on to figure how much money they are saving or making for us.
Cover crops need to be tailored to the farm where they are being used. The farmer also needs to be comfortable with the management aspect. Covers like cereal rye and those that winter kill are a good way to get a foot in the door. We have not yet tried interseeding or mixes with a dozen or more types of seed in them. There is plenty to learn and be gained from careful management of cover crops.
Brian Scott raises corn, soybeans, popcorn, wheat, and kids on an Indiana farm and blogs under the name The Farmer’s Life. His goal is to promote the virtues of modern agriculture and feature the operations of his farm.