Cover Crops

A major reason why farmers associate cover crop adoption with risk or potential yield drag is because they experience cases in which important cover crop management considerations may not have been effectively accounted for, leading to detrimental cash crop outcomes. Like many regenerative farming practices, successful cover crop management requires a holistic systems-based management approach that takes into account numerous aspects of agronomy. Several of these vital aspects of cover crop management are highlighted below:​

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Cover Crop Lifecycles 

One primary reason why cover crops are not a "one size fits all" solution is because each cover crop variety has specific lifecycle characteristics, including its planting window, phenological stages, cold tolerance, vigor, pest/disease susceptibility or tolerance, and termination window and methods. If a cover crop is not planted within a reasonable window, it may not manage to emerge and produce a stand of biomass that offers any agronomic benefits. On the flipside, if a cover crop is not terminated at the proper phenological stage, it can go to seed and become a noxious weed that robs the cash crop of nutrients rather than helping provide nutrients as decaying crop stubble. If a cover crop is roller crimped or mowed too early it may regrow and rob the cash crop of nutrients instead of serving as weed suppressive dead biomass. It is very important to account for the lifecycle and phenological characteristics of cover crops to realize the benefits they can offer and mitigate risks. Consulting a cover crop expert, performing online research, and discussing cover crop adoption with cover crop seed dealers are all valuable ways to gather insights on how to account for cover crop variety lifecycle traits and maximize agronomic success. ​

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Carbon-to-Nitrogen Ratio

Managing nutrients in conventional agronomy commonly focuses solely on plant nutrients (e.g. N, P, K, Ca, Mg, etc) in soil. Regenerative agronomy and soil health management expands on nutrient management to consider carbon as a valuable factor in soil biological activity and nutrient cycling. Carbon is the "food" that is often the biggest limiting nutrient for microbe growth. As microbes break down crop residue to obtain carbon, they then become limited by the second limiting nutrient they need to grow, nitrogen. Measuring and managing the ratio between carbon and nitrogen (C:N ratio) is vital to optimize crop residue breakdown and maximize cover crop soil fertility benefits. Grasses and grains like cereal rye typically have a high C:N, meaning that when these cover crops are terminated they introduce high levels of carbon-rich biomass to the soil. This feeds carbon to microbes and helps support their growth. However, as microbes break down the cereal rye biomass, they begin to need nitrogen to meet their needs for growth, and will "steal" plant-available nitrogen as a result. This process of soil microbial consumption of nitrogen is referred to as nitrogen immobilization, and is known to reduce the availability of nitrogen to crops in the short-run, while still retaining the nitrogen in microbial biomass for availability later on in the long-run. This is why cereal rye is commonly avoided as a cover crop before corn; because the high carbon cereal rye biomass can immobilize or "tie-up" nitrogen that the corn crop needs and lead to yield declines. In contrast, legume cover crops like vetch and clover have a low C:N, meaning they contain nitrogen-rich biomass. Cover crop residue from legumes thus has the opposite effect of cereal rye. Instead of "immobilizing" nitrogen, legume cover crops release nitrogen that both microbes and the cash crop can uptake. This explains why nitrogen hungry crops like corn tend to yield better following a legume cover crop. The nitrogen-rich biomass of legumes typically is broken down faster than carbon-rich biomass from grasses like cereal rye, offering less benefits in terms of weed suppression and soil cover. Using soil health tests like the Haney Soil Health Test, that measures the carbon-to-nitrogen ratio of the soil can offer insights on if a field will benefit more from a grass cover crop, legume cover crop, or a mix. Generally, if soil has a high C:N (14:1 or higher) then nitrogen is the limiting factor and the soil will benefit more from a legume that will introduce more nitrogen into the soil system. If soil has a low C:N (8:1 or lower), then carbon is the limiting factor and the soil will benefit more from a grass that introduces more carbon into the system. The ideal carbon-to-nitrogen ratio range on a Haney Soil Health Test is 10:1-12:1. For more details on managing carbon-to-nitrogen ratios, feel free to explore this resource from Soil Health Nexus. ​

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Additional Avenues for Profitability

Cover crops are commonly looked at as a tool to solely benefit the soil and following crop when managed effectively. While it has been widely proven that cover crops can offer economic benefits by improving soil health and supporting cash crops, their are many other potential avenues for profit that cover crops offer. Many regenerative farmers, like Gabe Brown, mimic natural rangeland environments by integrating livestock to graze on cover crops. Cover crops can offer nutritious forage for livestock, especially when planted as cover crop mixes. Regenerative row crop farmers are increasingly leveraging cover crops by diversifying their operations with livestock, or by offering their cover crop fields to neighboring livestock operations for forage. Livestock in turn cycle nutrients by leaving manure and urine rich in organic nutrients to benefit soil biology. Innovative technologies like electronic livestock collars are making it increasingly possible to integrate livestock without the laborious task of installing livestock fencing on row crop fields under cover crop production. Another alternative avenue for cover crop profitability is the harvesting of cover crop seeds. Organizations like Cover Crop Exchange offer farmers the opportunity to both buy and sell their cover crop seed. Beyond cover crop seed sales, value-added products like honey or even cut flowers, like sunflower, serve as additional revenue opportunities that cover crops can offer. These are just a few examples of ways that successful regenerative farmers are leveraging cover crops for additional revenue avenues beyond the agronomic benefits to soil health and cash crops that cover crops offer. 

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Equipment Considerations​

Successful regenerative farmers commonly pair cover crops with no-till management since no-till methods and equipment are designed to manage soil systems with a high degree of surface crop residue biomass and maximize the benefits of cover crops. Adopting cover crops in a conventional tillage system may go poorly if conventional seed drills are expected to tolerate cover crop surface residue. Instead, no-till planters are commonly used to plant into cover crop stands or residue. Similarly, integrating proper termination equipment such as roller crimpers, mowers, tillage implements, and herbicide sprayers is absolutely essential to effectively manage cover crops and maximize agronomic benefits while minimizing the risks of mishaps like cover crop residue plugging planting equipment or failing to terminate as intended. Before cover crops are integrated into a rotation, growers should always identify their equipment needs and be certain that their planting and termination capabilities fit their cover crop species or mix. The cover crop traits and profiles detailed in the next section provide guidance on planting and termination strategies for specific cover crop varieties.​

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Intercropping / Interseeding

Intercropping or interseeding involves planting cover crops into cash crops before harvest using a broadcast seeder, high clearance drill, or drone seeder. This allows cover crops to get a head start on establishment, scavenge nutrients, suppress weeds, and potentially fit within shorter seasonal planting windows than cover crops planted in fall after harvest. Cover crops are commonly interseeded into corn around the V4-V7 stage while soybeans are interseeded with cover crops at R1-R3. Beyond interseeding cover crops during cash crop rotations, some regenerative farmers have managed to successfully plant their cash crops into cover crops and then terminate the cover crop with a roller crimper while the cash crop is emerging. This practice is referred to as "planting green" and is practiced by successful regenerative organic no-till farmer Rick Clark of Indiana. Planting green ensures that a thick weed suppressive mat of cover crop residue is freshly terminated right as the cash crops are emerging. 

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Cost-Share Programs

Cover crops are widely considered an additional cost for farmers due to the inherent costs of seed, planting passes, and termination passes. While successful regenerative farmers often offset these costs by reducing fertilizer needs, minimizing crop protection product costs, and/or improving soil health and water retention, there are additional ways to reduce the cost of adopting cover crops. Several federal USDA and state-level programs offer incentives or cost-share initiatives that can compensate growers for using cover crops. A shortlist of some of these programs is provided below:

• USDA NRCS Environmental Quality Incentives Program (EQIP) 

• USDA NRCS Conservation Stewardship Program (CSP)

• Farmers for Soil Health Cover Crop Program

• Soil and Water Outcomes Fund

• No-Till on the Plans Cover Crop Cost Share Program

• Practical Farmers of Iowa Cover Crop Cost-Share Program

• Illinois Cover Crops Premium Discount Program​