This appeared in an article I wrote for Farm World not to long ago on cover crops. Personally, I'm for them.
Cover crops have long been used for maintaining soil productivity. Their use in the modern age, however, has been minimal with improved crop genetics, synthetic fertilizer, pesticides and better machinery. It is just in the past few years that producers have been giving cover crops a fresh look. A new survey released by the Sustainable Agriculture Research and Education (SARE) program in conjunction with the Conservation Technology Information Center with help from the American Seed Trade Association and Purdue University has found that a clear majority of farmers have a new appreciation for cover crops.
The survey of 2,020 farmers from across the country reflected enthusiasm for cover crops and – for the fourth year in a row – found a yield boost in corn and soybeans following cover crops. Multi-year data from the survey shows the yield boost increases as cover crops are planted year after year, a revelation that points to an appealing long-term benefit of the conservation practice.
Farmers have reported from the survey that corn yields rose an average 3.4 bushels per acre, or 1.9 percent, after cover crops, and soybean yields increased 1.5 bushels per acre, or 2.8 percent. Analysis of the survey data revealed that yield increases rose to 8.3 bushels per acre of corn after cover crops had been used for more than four years on a field. In soybeans, the average yield gain increased from 0.1 bushel per acre after a single year in cover crops to 2.4 bushels after four years of cover crops. Of the farmers surveyed, 33 percent found their profit improved as a result of using a cover crop, while only 5.7 percent said their profit decreased. The remaining responses were split between those reporting no change in profit and those not yet having enough data/experience to evaluate profit impact.
“Cover crops really shine in challenging years, when the improvements they influence on soil moisture holding capacity and water infiltration can minimize cash crop yield losses to stress,” said Rob Myers, Regional Director, Extension Programs for SARE at the University of Missouri. “In a favorable growing season, we expect to see less of a yield impact. However, the link between the length of time in cover crops and yield improvements points to the long-term benefits of building soil health. It’s also important to note that two-thirds of this year’s survey respondents agreed that cover crops reduced yield variability during extreme weather events. These farmers are taking the long view and recognizing that not every season turns out like 2015.”
Other highlights of the survey include:
* Cereal rye was the top species of cover crop planted by survey respondents, planted by 82 percent of the group and covering 187,044 acres among the participating farmers.
* A majority of respondents -- 52 percent -- reported that their soybean yields always or often rise after a cover crop of cereal rye; less than 4 percent said their yields sometimes or always decreased after rye.
* Cereal rye cover crops also proved helpful in other ways, with 82 percent of farmers reporting that the rye helped with weed management -- including 26 percent who found it also helped with tough herbicide-resistant weeds.
* Crimson clover was the most widely planted legume cover crop, while oilseed radish is the most common Brassica (mustard-type) cover crop species.
* Farmers were asked what would help motivate other farmers to adopt cover crops or increase their use; the top-ranked response was tax credits, followed by getting a discount on their annual crop insurance premium payment.
Cover crop mixes are gaining popularity. In all, blends of species were planted on nearly as many acres as cereal rye among survey respondents. Most – 61 percent -- said they designed their own blends, while 22 percent rely on advice from their cover crop seed salesperson or crop consultant for advice on mixing species.
“Several factors have led to the increase in the past few years,” said Andy Clark, Communications Director for SARE who has been working with cover crops for over 30 years. “Farmers seeing other farmers doing it have really helped grow the popularity in the past few years. University studies have so much influence, but when farmers see their neighbor planting them, they are more inclined to do it themselves. They are also seeing that it actually does help the soil. Climate change has been another factor. It looks like the use is going up and going up at a pretty fast pace. So far, there aren’t a whole lot of downsides to it.”
Lee Meyer, extension professor of sustainable agriculture at the University of Kentucky College of Agriculture, Food and Environment (UK), echoes Clark’s sentiment on the recent growth of cover crop use. “One of the things that is driving this is the recognition of cover crops and their value as well as the research projects which are going on. Probably one of the biggest parts of it, however, is just farmers sharing information with each other. The farmers that we’ve seen haven’t just been little guys. We have heard of producers upwards of 10,000 – 15,000 acres using cover crops.”
The benefits of cover crops are numerous and depend on the type of crop used. Primary uses include soil erosion reduction, adding organic matter to improve the soil, reducing weed problems as well as providing winter and early spring grazing. Since the development of no-till cropping systems, cover crops are known for their ability to provide moisture-conserving residues as well as nitrogen for the succeeding crop. They can take up and hold nutrients, especially N, which were not used from the previous cash crop.
“For a lot of growers, there is an interest in improving soil infiltration rates,” said Erin Haramoto, assistant professor of weed science at UK. “ There are a number of benefits. Row crop growers are little more limited because they have a shorter window than vegetable growers.
Cover crops vary depending on the type of crop planted. They can be broken down into two categories: Legumes and Non-Legumes. Legume cover crops (clovers, vetch, peas and beans) fix a lot of N for subsequent crops, due to N-fixing bacteria that live in nodules on the plant roots. These types also prevent erosion, support beneficial insects and pollinators and can increase the amount of organic matter in soil.
Non-legumes include grains (rye, wheat, barley, triticale and oats) and forage grasses (annual ryegrass). These are most useful providing erosion control, suppressing weeds and adding organic matter to the soil. Grains are very effective winter cover crops. They can also be harvest as forage, straw, grain or left in the field to provide mulch and organic matter to the soil. The grasses can be used as a winter cover crop, although it may winter-kill in some years. When planted in August or September, it usually produces good top growth before cold weather, helping it better to survive. However, even if they do winter-kill, they will still protect the soil. Cereal rye is generally the most popular in the Midwest due to the flexible window in which it is able to be planted.
If desired, all legumes can be seeded with a small grain. This will improve the soil cover, which is especially important on highly erodible fields, and improves the chances for winter survival of at least one crop. When using a mixture, a reduction of seeding rate of each by one-half is generally recommended.
Before any of this can happen, however, the cover crop must first be terminated in order to reap the benefits. Herbicides are one of the more popular methods with row-crop growers, however, different covers require different applications. The more affordable method is a winter-kill termination which is possible in most areas of the Midwest, however this is not an option for some of the covers. Oats and oilseed radish are two of the more common winter-kill covers. Tillage can also effectively terminate some cover crops, however this method has lost popularity as it reduces some of the benefits such as erosion control and building of soil organic matter. Mowing or using a roller-crimper can also terminate covers at the flowering or heading stage.
“For non-organic growers, herbicides are the most popular,” said Haramoto. “For organic growers, it is a little more challenging because they have to rely on tillage or mowing or using a roller crimper since they are not able to use any chemicals.”
Haramoto says that those who do not show an immediate profit should not be downhearted. “Economic benefits that growers see are hard to put a dollar value on,” she explained. “They occur over the long term such as changes in soil health, increasing organic matter and reducing soil erosion. It has been shown that the first couple of years of growing cover crops, the economic impact may not always be favorable as growers are still learning how to use them. There is a learning curve involved. There might be lower yields the first couple of years because they are still working out their seeding and growing strategies. Over the long term, however, there is an economic benefit.”
She says that the growers of vegetables and tobacco may be able to see a more immediate economic benefit. Using legumes, they will probably be able to cut their use of N down as those crops will add N to the soil more so than the non-legumes; as much as 50lbs per acre.
Both Clark and Haramoto are encouraged by the fact that cover crops are remaining popular despite the decline in row crop prices. “I was worried that with commodity prices going down, we would see a decline in cover crop usage, but that isn’t the case,” said Clark. “I’m encouraged because it seems that the use is rising through both higher and lower prices. It seems like there is nowhere but up.”
More detailed information can be found by going to http://www.sare.org/CoverCrops. For information about a specific regions, producers should contact their local extension agent.