Continuous Living Cover

Agroforestry is a land management approach that integrates trees and shrubs with plant and animal farm operations. USDA describes it as “combining trees and agriculture to enhance long-term production of food and other useful products while protecting the soil and water, diversifying and expanding the local economies, providing wildlife habitat, and ensuring a more pleasing and healthy place to work and live.”

There are five types of agroforestry:

1. Silvopasture is when trees, livestock, and forages are grown together.
2. Alley cropping is when agricultural and horticultural crops are grown between rows of woody plants, like when corn is planted between pecan trees.
3. Forest farming or multi-story cropping combines forestry with small-scale farming or gardening of high-value crops like ginseng and mushrooms.
4. Windbreaks are used to protect soil and improve crop yields as well as control snow drifts and improve wildlife habitat.
5. Riparian forest buffers use trees and other plants to protect waterways from the negative impacts of agricultural fields.

Environmental Benefits

• Helps store carbon in soil, mitigating greenhouse gas emissions
• Reduces soil erosion
• Improves soil health
• Can change the microclimate, which may improve crop yields and protect livestock
• Protects streambanks
• Minimizes water pollution
• Protects water quality and ecosystems
• Creates wildlife habitat and connectivity across fragmented agricultural landscapes
• Protects biodiversity and creates habitat for wildlife, pollinators, and beneficial insects
• Conserves energy
• Produces bioenergy
• Leads to more sustainable farms, ranches, and woodlands

Perennial biomass crops are perennial plants that are grown and used for renewable energy. They can be grown as cover crops, perennial grasses, and short-rotation trees. Many of these crops can also be used as forage for livestock. While not widely produced for energy needs now, perennial biomass crops offer a renewable energy source with ecological benefits. Compared to grain ethanol crops, growing perennial biomass plants may benefit the environment rather than harm it by storing carbon in soil, and requiring less fuel, fertilizer, pesticides, and water. They can be managed to reduce soil and water erosion, build healthy soil, and increase wildlife and pollinator habitats. Beyond uses for fuel/renewable energy, the application of perennial biomass crops is also being explored in the emerging field of “plant-based chemistry” (also known as “green chemistry”). Innovative industrial applications of bio-based products could span a wide range of industries, including everything from cosmetics and packaging to automotive and construction markets.

Switchgrass (Panicum virgatum), a highly productive hay and forage crop native to the Midwest, is an example of a perennial biomass species. Studies have shown that grown as a biomass crop it would protect water, soil, and air quality, increase biodiversity, and create wildlife habitat.

Environmental Benefits

• May reduce CO2 emissions by storing carbon in soil and requiring less greenhouse gas-emitting fuel to farm it
• Does not deplete soils
• Reduces soil and water erosion
• Creates wildlife and pollinator habitat
• Increases biodiversity

Perennial forage refers to land planted with perennial plants that feed livestock like alfalfa, white clover, and red clover. Perennial forage plants can be grown as cover crops or in rotation and are eaten by grazing animals or harvested and fed to livestock as hay or haylage after the growing season is over. Perennial forage fields act like a sponge; they absorb water and nutrients and allow very little of either to escape into groundwater or surface water. Farmers also use perennial forage plants like alfalfa to enrich their soil with nitrogen before planting row crops of corn, which has the added benefit of higher yields due to fewer insects and better soil tilth.

Managed grazing is a way to feed livestock by rotating animals through different pastures or cover-cropped fields using lightweight fencing that can be quickly and easily moved. Livestock are moved in response to their nutritional needs and the amount of forage that is available. Animals can be grazed to enhance soil biology and manage invasive species in specific areas. Carefully managed grazing can benefit the environment by improving soil, reducing runoff and soil erosion, creating wildlife habitat, sequestering carbon, and conserving resources. However, studying the environmental benefits is challenging and additional research is needed to fully understand its impact on carbon sequestration and conservation.

Environmental Benefits

• Improves soil health
• Reduces soil erosion and nutrient losses
• Adds nitrogen to soil
• Controls invasive species
• Helps mitigate water contamination due to the leaching of nitrates
• Legume forage crops can break disease cycles and cut down on weeds and pests
• Provides habitat for wildlife, birds, and beneficial insects

Unlike annual grains, perennial grains are crops that are alive year-round and are productive for more than a year. They offer a variety of environmental benefits compared to annual crops that dominate agriculture today like wheat, corn, and soybeans. They can have deeper root systems and longer growing seasons and therefore absorb and hold more rainwater and better capture nutrients – leading to less runoff and erosion. Compared to annual crops, perennial grains maintain and capture more carbon in soil, require smaller amounts of fertilizer and herbicide, and need less tillage. Because they don’t need to be tilled each year, perennial grains could build soil and store carbon rather than deplete and release it as annual crops do.

Kernza® (Thinopyrum intermedium) is a promising new perennial grain species being developed by the Land Institute in Kansas and the University of Minnesota’s Forever Green Initiative to be an edible grain with environmental benefits. It’s the first perennial grain commercially available in the U.S., and it offers a way to curb greenhouse gas emissions and lessen the impacts of climactic warming by shifting agricultural practices.

More work on the grain needs to be done to improve yields and lifespan beyond a few years (the grain only produces 10-20% of what wheat yields now) and to produce a crop that’s better for baking (Kernza® has more protein in it than conventional wheat, but it’s got less of the protein needed for dough-strength). While there is a lot of interest in Kernza® and products made with it, supply is limited and more research is needed to develop a grain that meets widespread market demands. Researchers are also working to develop perennial wheat, sorghum, and rye species.

Environmental Benefits

• Uses nutrients more efficiently than annual crops
• Requires less tillage
• Traps more atmospheric carbon than annual crops
• Maintains carbon levels in soil
• Builds soil organic matter
• Reduces erosion and nitrate leaching
• Uses less water than annual crops
• Captures and retains more water than annual crops
• Filters more water
• Reduces the need for fuel, fertilizers, and pesticides
• Protects wildlife habitat and provides habitat for pollinators and beneficial insects

Cover crops are legumes, grasses, and other forbs planted within the regular growing season or outside it to improve or maintain the ecosystem (United States Department of Agriculture). In the Midwest cover crops are often used between corn and soybean plantings to protect and add nutrients to the soil. Winter-hardy perennial grasses and legumes add year-round ground cover to fields. Having roots in the ground when other crops aren’t growing helps to keep soil in place and minimize erosion. Cover crops support annual crop production by helping to break disease and pest cycles and they can also be used for animal forage. Biomass from cover crops can be used for animal feed and bio-energy.

Promising new winter annual crops being developed at the University of Minnesota include:

Pennycress (Thlaspi arvense) – a winter annual oilseed species being developed as a rapid-cycling winter cover crop and biodiesel feedstock.
Camelina (Camelina sativa) – a high-quality edible oil seed crop with the potential to be a cash cover crop that benefits ecosystems and farmers.

Environmental Benefits

• Stores carbon in soil
• Improves soil quality
• Adds nitrogen to soil
• Reduces erosion and pesticide runoff
• Retains more water and improves water quality
• Retains nutrients that would otherwise be lost
• Reduces flooding and leaching
• Helps to break weed, pest, and disease cycles
• Reduced use of fertilizer
• Increased biodiversity
• Creates wildlife habitat
• Attracts honey bees and beneficial insects

For more on the why behind CLC, link to the “making the case for CLC” section of our website.

Annual row crops in the Upper Midwest leave the ground mostly bare for two-thirds of the year and have replaced native prairies and woodlands that, until the mid-1800s, covered the land all year, supported diverse wildlife, and built rich soils. Below ground the more transient roots of crops that grow during a single season have replaced the naturally deep, dense mesh of perennial roots. These changes allow large volumes of soil and nutrients – valuable farm inputs – to wash into lakes and streams and contaminate groundwater, damaging aquatic ecosystems and threatening human health. Soil health is reduced and native plant and animal habitat is lost, including critically important pollinators. Our diminished land and water resources are increasingly vulnerable to weather extremes.

Continuous Living Cover farming addresses issues inherent to our current agricultural system, which is bolstered by well-established supply chains, policies, and dominant agricultural narratives supporting a small number of crops. These issues include:

• Intense production of a few crops on many acres;
• Constrained economic opportunities;
• Negative environmental impacts.

With CLC, farmland stays in production, making good, year-round use of soil, nutrients, water, and solar resources. CLC farming introduces a greater diversity of crops and livestock. Water quality improves; stream flow is moderated; soil health improves and is sustained. Native wildlife species have more suitable habitat. New economic opportunities can develop for farmers and their communities. With CLC practiced widely, we contend that our land, water, farms, and communities will be more environmentally and economically resilient.

There are many types of CLC crops and systems and many ways they can be combined to meet the interests of farmers and landowners.

• Summer annual crops can be rotated with winter annual crops that are grown as either a cover or cash crop harvested in spring.
• Perennial grasses and forbs grown as hay crops and in pastures support the return of livestock to farms and have environmental and economic benefits.
• Grazing of cover crops within row crop acres can also be a way to re-integrate livestock.
• Tree and shrub crops produce fruits, berries, nuts, wood, fuel, and fiber.
• Herbaceous and woody perennials create biomass for fuel and industrial products.
• Further expansion of CLC farming will come from new varieties of perennial grain crops that lead to products similar to high-demand commodity crops, but with more positive impacts on soils, water, and wildlife.
• Perennial crops and annual crops can be grown in multi-year rotations and their locations in fields and on farms can shift to achieve more cumulative CLC acres, adding up to landscape-scale change.