In recent years, interest in adding cover crops has increased and potential benefits have become more widely recognized. From nitrogen (N) and nutrient management to soil health and carbon credits, there are numerous reasons why growers may consider adding cover crops to their farms. But cover crops are not for every field, or even every grower.
“What’s your goal with cover crops?” asked Kevin Fry, Pioneer Field Agronomist. “While forages and erosion control are the top methods in most places, growers need to define their goals before planting a single seed.”
The most commonly used cover crops fall into one of three broad groups: grasses, legumes and brassica.
Grasses, including winter cereals such as rye, wheat, barley and triticale, are the most widely used cover crops in corn and soybean cropping systems. In general, these grasses are best suited for scavenging soil nutrients, preventing soil erosion and suppressing weeds.
Legumes are valued as cover crops primarily for their ability to fix N. Common legumes used as winter cover crops in corn and soybean cropping systems include hairy vetch, field pea, lentil, crimson clover, red clover and berseem clover.
Brassica cover crops, such as radish or winter canola, have grown in popularity recently due to their ability to provide many of the same benefits as grasses but with residues that break down more rapidly in the spring. Certain brassicas are also becoming well known for their ability to produce a large taproot that is effective at minimizing soil compaction.
It is important to note that cover crop suitability varies by region. Minimum annual temperature is a good predictor of how well adapted a cover crop is to a location. This article from Pioneer provides an overview of the geographic adaptability of cover crops.
Growers also need to consider how and when to terminate their cover crops. Winterkilling, tilling, mowing and herbicides are the four main methods. Winterkilling is highly effective but only applicable to certain cover crops. Similarly, while tilling legumes can help increase N availability, it is less desirable for grasses that produce greater quantities of low-N biomass. Due to simplicity and efficacy, many growers prefer to terminate cover crops using herbicides.
Research studies on the effects of cover crop on grain yields vary depending on environment, cover crop species and management. Getting the greatest benefit out of cover crops requires a management level on par with corn and soybeans. Growers should start by testing a cover crop on a single field and expand.