Previously I discussed how cover crops are grown for the protection and enrichment of the soil, and are one of several management practices that farmers use to improve soil health, but noted there were some potential barriers to their adoption.
The USDA report “Cover Crop Trends, Programs, and Practices in the United States” indicated that cover crops have some associated costs that may be limiting their adoption. While costs are a concern, there are other challenges to their continued widespread adoption. Research and experience are showing that some of these are misconceptions and should not slow the adoption of cover crops.
One of the oldest concerns I have heard is that cover crops will delay planting, resulting in decreased yields. A survey conducted by the Conservation Technology Information Center found that farmers who use cover crops were more likely to plant earlier due to improved conditions from the cover crop. Also, the ability of cover crops to build soil structure and enhance drainage under the soil surface enables fields to absorb heavier rain events that might overwise run off.
Having the knowledge and management ability to understand when to terminate a cover crop is important. As farmers learn how to manage cover crops, their ability to make timely decisions improves. Farmers who are just starting to use cover crops are encouraged to start small and learn what works for them.
Cereal rye was one of the first crops used as a cover crop. It presented some challenges, especially when the cover was terminated and decomposing into soil organic matter. Once researchers realized that the carbon-to-nitrogen ratio (or green-to-brown ratio for composters) was out of balance, the addition of other plant species, such as clover or peas, into the cover crop seed mix helped bring the balance in line.
As mentioned before, cover crops improve the soil structure by increasing soil organic matter. Soil organic matter helps to retain soil moisture. This moisture can become available to an actively growing crop under drought conditions.
Another misunderstanding about cover crops is they will keep soil temperatures colder in the spring, resulting in delayed planting. This concern most likely is rooted in the introduction of no-till planting to the northern climates, including New York. Farmers did see a delay in planting under a no-till system as soil temperatures were slow to warm. Cover crops, however, are living plants and not last year’s crop residue. As living plants, they keep the soil warmer and support the millions of active soil microbes when compared to a soil surface without a cover crop.
While the cost of the seed for the cover crop is an additional expense, research and experience has allowed for the successful establishment of cover crops using less seed. There are now companies specializing in improving the genetics of cover crop seed. Cover crops are becoming part of a crop rotation with farmers purchasing seed with performance, purity and germination in mind. In 2012, the National Cover Crop Survey determined the average seed cost for cover crops was $25 per acre. The 2020 survey found that these seed costs ranged from $11 to $20 per acre. More information about the recent National Cover Crop Survey results can be found at sare.org/wp-content/uploads/2019-2020-National-Cover-Crop-Survey.pdf.
Cover crops are not just used on cash crop farms. Vegetable growers and horticulture producers also use cover crops. They too find the benefits of improved soil health, reduced erosion and weed suppression. Horticulture producers noted additional challenges associated with high traffic areas in orchards and vineyards. This challenge is addressed with cover crop seed mixes that can withstand the heavy traffic patterns over a period of years.
Meanwhile, vegetable growers have found that cover crops may assist in the management of some soil diseases that can be detrimental to their vegetable crops. They also found cover crops helpful in the management of nematodes, which are very small worms that are part of the food web in a living healthy soil. Some nematode species carry and transmit plant diseases, causing damage and yield reduction. In this case, cover crops are considered a form of biological control and may reduce or eliminate the need for chemical control.
As the adoption of cover crops continues to increase, I am hopeful misconceptions about cover crops will continue to be dispelled. Cover crops provide many benefits, such as improved soil health, reduced erosion, weed suppression and the potential reduction in fertilizer and herbicide use.