If you’re looking for a cover crop that also can serve as a cash crop, then pennycress might be something to consider.
This fall-planted, non-edible brassica can provide economic returns up to 990 pounds per acre, or 45-50 bushels per acre, with a seed oil content of 26-39%, says University of Minnesota Extension.
Metro Ag Energy, a Michigan cooperative that processes pennycress oil into biodiesel, says farmers who grow the plant can increase farm profits by up to 50%. With its high oil content, one acre of pennycress can result in 100 gallons of oil.
Like many other types of cover crops, pennycress — which is part of the mustard family — helps with preventing soil erosion and nutrient leaching, while suppressing early-season weeds. It’s also attractive to beneficial insects and pollinators.
Pennycress is typically planted anytime between the second week in September through the third week in October, and only 5-10 pounds of seed per acre is needed for a sizable crop. For best results, Metro Ag Energy says, pennycress should be planted when soil is at 85% moisture or higher.
Broadcasting pennycress has been shown to result in a higher germination rate, as the seed has more access to sunlight — although drilling has shown to result in better stand establishment and higher yields.
Researchers have tested pennycress in both double and relay cropping systems in the Upper Midwest, with positive results. A combined crop of pennycress and soybeans yielded a larger soybean harvest than soybean fields without pennycress. Information from Metro Ag Energy stated that some farmers who planted soybeans after harvesting pennycress saw a boost in soybean yields of 2-5 bushels per acre.
The presence of pennycress in fields also reduced the nitrogen (N) content in the soil profile by 18-19%, which means less chance of N leaching and potentially contaminating local water supplies. Pennycress has also been shown to suppress nematodes and also deters pesky wildlife like deer and birds.
Another benefit to pennycress as a cover is that once it’s been seeded, the crop is on its own until harvest. No additional maintenance is needed.
Water availability is the major limiting factor for pennycress to germinate and develop, so it’s susceptible to moisture stress and might not be well-suited for growing in arid environments.
The length of winter and amount of precipitation are highly influential in determining when pennycress reaches maturity and can be harvested. Soil temperatures also account for 63% of variation in seed oil content at harvest, while precipitation accounts for 86% of variation. Studies have shown that earlier planting can result in a higher oil content.
Pennycress is inexpensive to grow, as it doesn’t require any fertilizer or additional nutrients. Being a cold-weather crop makes it ideal for growing over winter in the Midwest and being harvested in May, effectively adding a third growing season for farmers.
No special equipment is needed to plant or harvest pennycress, making it a practical choice for growers. Pennycress yields twice as much oil as soybeans, which makes it a highly efficient source of biodiesel that exhibits enhanced cold weather performance.
Leftover cake or meal from the oil pressing process can be used as either biomass, organic fertilizer or livestock feed. Pennycress seed meal has been shown to provide 100% weed suppression when incorporated into the soil.
Researchers have just started putting efforts toward looking at pennycress as a cover crop in the last decade, and more research is being done on optimal planting and harvesting dates for pennycress and evaluating the crop for N use efficiency. Expect to see more information coming on this exciting new cover crop.