Cash crops like corn, soybean, wheat, rice, and cotton are responsible for most of the food and fiber consumed by humans and animals around the globe1. These annual crops and others are usually only growing on farm fields for about half of the year. Growing seasons are usually April through September or September through July, depending on the crop and area of the country. After harvest, the soil can lay bare. This can lead to several problems:
- Harmful wind and water erosion causes loss of nutrient-rich topsoil.
- Weeds more easily invade bare soil.
- Future crop yields tend to decline drastically.
- Run-away soil can also be harmful to the environment.
- Eroded soil is costly to replace – in nature it can take thousands of years to replenish just one inch of topsoil.
- Lack of plant cover can increase nutrient runoff, as well as movement of pesticides into adjacent areas.
Increasingly, growers are turning to cover crops to help them solve some of these problems. Cover crops are not grown for their cash value. They are planted primarily to improve or maintain ecosystem quality.
Cover crops are an excellent way to help address some of the listed concerns. They also provide many other benefits to crop production. They increase the soil’s organic matter, thereby increasing cash crop yield. Many types of cover crops can add nitrogen to the soil via nitrogen fixation. Their presence suppresses weeds and adds crop diversity on the farm. Cover crops reduce soil compaction, and attract beneficial insects. In short, they can help protect and build the health of soil in crop fields and reduce negative impacts of agriculture on the environment.
Cover crops should be tailored to address the concerns and/or desired benefits of each crop field. Selecting the right specie(s) is the first step for successful cover crops. Decades of public and private research combined with experience by farmers have led to various cover crop selection tools. These tools help farmers select among 30 or more plant species. Some growers even make a custom mix of several species. Cover crop options are usually broadly classified into three categories:
- Legumes such as clover, pea, and bean species – these add nitrogen to the soil.
- Brassicas such as mustards and radish species – their deep root systems help reduce soil compaction.
- Non-legumes such as oat, barley, rye, wheat, millet species – these are economical and grow fast to help hold nutrients and protect soil from erosion.
Selecting the right cover crop for a farm – and year – will depend on the length of the growing season desired.
The benefits of cover crops come at a cost. Farmers may spend anywhere from $10 to $40/acre to grow cover crops. This isn’t a trivial amount! Despite the added cost, many farmers are realizing benefits and improved cash crop returns within five years of use. They consider cover crops a long-term investment for their enterprise. In fact, recent data indicates that cover crop use in the United States is increasing rapidly. A 2017 survey of 2,000 farmers found that 88% were using cover crops, and that the average cover crop acres per farmer had doubled since 20122.
While cover crop use is increasing in the United States and other countries, hurdles to widespread adoption still exist. Some major concerns with cover crop use include extra time, cost, and labor with no additional income. Growers also have concerns about covers becoming weeds or using too much water. Farmers, researchers, educators, and policy makers across the globe are working to address these concerns. They are looking to discover feasible and economic ways to incorporate cover crops everywhere that the benefits of their use outweigh the negatives. Cover crops are not the “silver bullet” to solving all problems associated with agriculture, but they are an excellent solution for many farmers that will help sustain agriculture for future generations.
Answered by Matt Yost, Utah State University
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About us: This blog is sponsored and written by members of the American Society of Agronomy and Crop Science Society of America. Our members are researchers and trained, certified, professionals in the areas of growing our world’s food supply while protecting our environment. We work at universities, government research facilities, and private businesses across the United States and the world.