Cover Crops

Why is pennycress a good cover crop?

Soil is a living thing. It sustains life in many ways and plays a vital role in providing us with food, fuel, fiber, and shelter. Therefore, it is important to think about what we can do to protect this incredible resource for the present and future generations.

One of the methods farmers can contribute to protecting soil is with the use of cover crops. These are defined as “crops grown for the protection and enrichment of soil.” The benefits of the use of cover crops on agricultural land have been known for decades. However, the total acreage using these crops is extremely small. The main reason for that is that cover crops generally don’t turn a financial profit, so it is costly for farms to implement this great resource.

This is where pennycress comes in as a great alternative to traditional cover crops.

closeup of bumblebee on pennycress flower
Pennycress is an alternative cover crop for farmers in the Midwest. It not only provides cover crops services, like erosion control and providing pollen for pollinators, but it serves as a cash crop in its second season. The seeds have oil which can be used in biodiesel, bioplastics and as a source for inexpensive plant-based proteins. Credit: Zenith Tandukar

Pennycress bridges the gap between harvest for one year through to planting in the second year. While it grows, it actively provides benefits like other cover crops. It protects the soil against erosion, nutrient leaching, and early season weeds. It also acts as an attractive option for pollinators in early spring when other flowers are rare.

While pennycress serves as a living cover on otherwise fallow croplands, it also produces oil-rich seeds! This crop requires minimal additional nutrients after planting and its seeds can be harvested and sold to generate a profitable cash margin. Each acre of pennycress has the potential to produce 50-100 gallons of oil. Pennycress oil can be turned into renewable diesel or biodiesel.

However, oil is only one of the many use cases of pennycress. The crops also can be used to make bioplastics and is an inexpensive source of plant-based proteins. With proper infrastructure and supply chain optimization, using pennycress as a cover crop followed by harvest can substantially increase farm profits for US farmers. For this reason, pennycress has been called the “cash cover crop”!

side by side photo of pennycress cover crop plots in field, with one photo the same field covered in snow
Pennycress plots in their rosette stage will remain dormant for months under the snow and survive the extreme cold Midwest temperatures. The picture on the right is the same field 7 days after the first picture was taken after a snowfall. Pennycress can withstand snow and extreme cold (-30oF) and still provide an excellent cash crop the following year. Credit: Zenith Tandukar

The concept of bridging the gap between harvest and planting in much of the Midwest and Upper Midwest with a new crop is sometimes confusing. And rightfully so. This region experiences extreme snowfall and sub-zero temperatures for much of the winter and early spring. Fortunately, pennycress is extremely winter hardy. It can tolerate snowfall and snow cover, and extreme temperatures of -30oF with minimal damage.

Typically, pennycress gets planted during the fall and grows to a rosette stage before the heavy snow and cold temperatures arrive. Then it stays dormant for most of the winter under the snow biding its time for the snow to melt in the spring. When temperatures warm, pennycress enters the reproductive phase of its life cycle, flowers, and sets seed. This seed can be harvested and pressed for oil for renewable biofuels in its current state. It also has the potential to become an edible oil product like canola oil with the help of plant breeding.

As a cover crop, pennycress can play a powerful role in restoring soil biodiversity on the farm. Growing cover crops in the off-season is one of the farming practices that helps sequester more soil carbon and convert it to soil organic matter.

field of pennycress plants coming out of dormant stage with trees and sky in background
Pennycress plants come out of their dormant stage after the snow melts and enter their reproductive phase where they will first flower, and then set seed. These seeds are extremely oil rich with 29% – 40% oil (on average) and can be used as a source of oil for renewable diesel. Credit: Zenith Tandukar

In addition to soybean oil, U.S. biodiesel producers will likely need more oilseed options to achieve the ambitious goal of 6 billion gallons in the U.S. by 2030. This means that production will have to double today’s number to reach that goal and will depend heavily on new crops to support this industry.

Pennycress has enormous potential in the realm of sustainable agricultural intensification such that farmers use the same amount of land for more output, all while helping the farmer’s farm profits, protecting the environment, and promoting soil health.

Answered by Zenith Tandukar, University of Minnesota

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.

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