By Craig Sheaffer
A recent study entitled “Putting Down Roots: Analyzing the economic and environmental benefits of continuous living cover for Minnesota’s farmers, water and climate” has shown the environmental and economic impacts that alfalfa and perennial grasses have as continuous living covers (CLC). Other new CLC crops are being developed within the Forever Green initiative at the University of Minnesota to diversify our predominant summer annual cropping systems. The crop categories that were analyzed for environmental and economic potential include:
- Perennial forage and pasture (alfalfa, cool and warm season grasses)
- Perennial grains (Kernza, perennial wheat, etc.)
- Winter annual oilseeds (winter camelina, pennycress)
- Winter annual cereals and legumes (hybrid winter rye, winter pea)
- Woody perennials (hazelnut, poplar, elderberry)
- Perennial oilseeds (perennial sunflower, perennial flax)
Value of continuous living cover (CLC)
The study analyzed the potential for adding CLC crops to Minnesota’s agricultural landscapes that are now mostly used for the production of annual corn and soybean crops. It finds that increasing acreage of perennial forages and adding other new crops will increase the percentage of cropland soils that are protected by living roots and vegetation from 48% in 2023 to 77% in 2050. As a result, there is potential to reduce nitrogen and soil loss by 23% and 35%, respectively, compared to a corn and soybean cropping system that leaves soils without living winter cover.
The study also found that adding CLC crops will increase net farm return, creating an incentive for farmers to adopt them. Certain new crops such as camelina, an annual oilseed intended for use as a winter cover, may have more environmental and economic impact than the other new crops because of its potential as a sustainable aviation fuel. Other new crops might fit into specific on-farms land-use niches and be planted only on limited acreage. Conventional cover crops like winter rye are expected to provide <10% CLC. The challenges with currently used winter cover crops like winter rye are described in the article, Why did cover crops cause issues in Minnesota the last two years and what should growers do going forward?.
Perennial alfalfa and grasses provide superior CLC
While there is great appeal to the development of new crops, it is apparent that we need to take advantage of the unique traits of traditional perennial forage crops. Perennial forages are among the best crops in providing CLC and twice as effective as winter oilseeds in reducing soil erosion and nitrogen loss. By 2050 they are expected to provide 20% of the CLC! The multiple contributions of alfalfa, clovers and perennial grasses include:
- Year-round, multiple year vegetative cover that reduces wind and water erosion.
- Root systems that stabilize the soil, sequesters carbon, and supply significant organic matter to improve soil health and soil microbial populations. The root systems also can recycle nutrients in the soil and take up excess soil nitrate. When grown together, the root systems of alfalfa and perennial grasses are complementary.
- Rotation effects increase the grain yields of subsequent crops in rotation. This benefit occurs from biological nitrogen fixation and from improvement in soil health by both grasses and alfalfa. Alfalfa and clovers conduct biological nitrogen fixation that supplies nitrogen to the plant and to subsequent crops in rotations.
- Reduced pesticide and herbicide use on rotation crops through suppression of annual weeds.
- Food and habitat for pollinators, beneficial insects, and wildlife.
Economic benefits from perennial forages
Alfalfa alone or mixed with perennial grasses like orchardgrass, perennial ryegrass, and tall fescue is widely used as a source of high-quality feed for cattle and horses. Similarly, perennial grasses and clovers are the basis of many grass-fed dairy and beef systems. These forages are harvested for hay, silage, or pasture from over 3 million acres. A conservative estimate of the economic value of hay and haylage produced is over $600 million. Even so, use of alfalfa and grass pasture has declined in regions that are most in need of CLC and achieving the goals described in the report will be challenging.
How do we increase alfalfa and perennial grass acreage?
The new CLC crops lack breeding, agronomic research, and market development needed to increase acreage expansion. In contrast, alfalfa and perennial grasses have historically been used for livestock feed, but acreages have declined due to changes in livestock feeding practices. To maintain and achieve acreage goals for perennial forages stated in the CLC report here are some suggestions:
- Increase funding to support research showing the feeding value of alfalfa and perennial grasses in livestock rations.
- Improve federal risk management programs, such as crop insurance, to reduce production risk for alfalfa and perennial grasses so that they are on an equal playing field with commodity crops like corn and soybean.
- Provide funding to incentivize use of alfalfa and grasses for reducing soil erosion and nutrient leaching and for strategic placement of alfalfa and perennial grasses to remediate excess soil nitrogen and phosphorus.
- Develop new uses for alfalfa such as in fish feeds, nutritive supplements, alternative protein sources for human consumption, high-value chemical manufacturing, or other novel uses.
- Breed alfalfa and grasses to increase forage yield potential and or increased winter survival.
Source : umn.edu