The oilseed species Thlaspi arvense (pennycress)-a weed that was only recently removed from the wild-has the potential to provide new sources of food and bioproducts when grown as a winter cover crop. Domestication of wild species has historically taken hundreds to thousands of years, but by making use of large-scale high-throughput comparative gene and phenotype analyses, along with recently developed technological tools, it has been possible to greatly accelerate this process. By taking advantage of extensive gene and phenotype knowledge in the related plant Arabidopsis, mutations for early maturity, reduced pod shatter, reduced seed glucosinolates and improved fatty acid composition were identified. Progress has been made to rapidly stack these traits in order to domesticate the plant, allowing it to fit within current crop cycles and to have improved seed harvestability and nutritional content. Pennycress, domesticated as a winter cover crop, may provide new sources of food, animal feed and bioproducts-and solutions to food security.

Cover crops can serve as a valuable management tool for improving soil and water quality, but are an added expense for farmers. We evaluated the yields and economics of four cover crops and two winter fallow treatments in a spring wheat (Triticum aestivum L.)-soybean [Glycine max (L.) Merr.] rotation at three sites in Minnesota. The four cover crop treatments were winter rye (Secale cereal L.), forage radish (Raphanus sativus L.), winter camelina [Camelina sativa (L.) Crantz], and pennycress (Thlaspi arvense L.) planted into spring wheat stubble. The fallow treatments consisted of no-tilled and conventionally tilled soil. Radish winterkilled and rye was terminated chemically before planting soybean in early May. Soybean was inter-seeded between rows of camelina and pennycress at the same time it was planted in other treatments. Camelina and pennycress were harvested over soybean seedlings in late June. Camelina yields ranged from 600 to 1100 kg ha -1 , while pennycress ranged from 900 to 1550 kg ha -1 . Mono-cropped soybean averaged 1819, 3510, and 4180 kg ha -1 in northern, central, and southern Minnesota, respectively. Soybean seedlings under oilseed cover crop canopies exhibited lightstress, which likely reduced soybean yield in these treatments by 22 to 30%. When oilseed and inter-seeded soybean yields were combined, total seed yields generally were equal to or exceeded those of mono-cropped soybean. In addition, net income for inter-seeded systems was typically equivalent to mono-cropped soybean. Improvements in net income are likely needed before the benefits of oilseed cover crops are fully realized.• Net income from relay cropping was rarely different from that of mono-cropping. • A 25-cm oilseed row spacing was likely too narrow for optimal soybean growth. • Further domestication of oilseeds will likely improve relay cropping with soybean.

Agriculture in the Upper Midwest of the USA is characterized by a short growing season and unsustainable farming practices including low-diversity cropping systems and high fertilizer inputs. One method to reduce the magnitude of these problems is by integrating a winter annual into the summer-annual-dominant cropping system. For this reason, pennycress (Thlaspi arvense) has garnered interest in the agricultural community due to its winter annual growth habit and potential for industrial oil production, making it an ecologically and economically desirable crop. Despite decades of research focusing on pennycress as an agricultural weed, little is known about its best management practices as an intentionally cultivated crop. The majority of agronomic research has occurred within the past 10 years, and there are major gaps in knowledge that need to be addressed prior to the widespread integration of pennycress on the landscape. Here we review relevant agronomic research on pennycress as a winter annual crop in the areas of sowing requirements, harvest, seed oil content, seed oil quality, cropping strategies, ecosystem services, and germplasm development. The major points are as follows: (1) there is little consensus regarding basic agronomic practices (i.e., seeding rate, row spacing, nutrient requirements, and harvest strategy); (2) pennycress can be integrated into a corn (Zea mays)soybean (Glycine max) rotation, but further research on system management is required to maximize crop productivity and oilseed yields; (3) pennycress provides essential ecosystem services to the landscape in early spring when vegetation is scarce; (4) breeding efforts are required to remove detrimental weedy characteristics, such as silicle shatter and high sinigrin content, from the germplasm. We conclude that pennycress shows great promise as an emergent crop; however, current adoption is limited by a lack of conclusive knowledge regarding management practices and future research is required over a multitude of topics.

Winter cover crops might reduce nutrient loss to leaching in the Upper Midwest. New oilseed‐bearing cash cover crops, such as winter camelina (Camelina sativa L.) and pennycress (Thlaspi arvense L.), may provide needed incentives. However, the abilities of these crops to sequester labile soil nutrients are unknown. To address this unknown, N in shoot biomass, plant‐available N and P in soil, and NO3−–N and soluble reactive P in soil water collected from lysimeters placed at 30, 60, and 100 cm were measured in cover crop and fallow treatments established in spring wheat (Triticum aestivum L.) stubble and followed through a cover crop–soybean [Glycine max (L.) Merr.] rotation. Five no‐till cover treatments (forage radish [Raphanus sativus L.], winter rye [Secale cereale L.], field pennycress, and winter camelina) were compared with two fallow treatments (chisel till and no‐till). Pennycress and winter camelina were harvested at maturity after relay sowing of soybean. Winter rye and radish sequestered more N in autumn shoot biomass, ranging from 26 to 38 kg N ha−1, but overwintering oilseeds matched or exceeded N uptake in spring, ranging 28 to 49 kg N ha−1 before soybean planting. Nitrogen uptake was reflected by reductions in soil water NO3−–N during cover crop and intercropping phases for all cover treatments (mean = 4 mg L−1), compared with fallow treatments (mean = 31 mg L−1). Cash cover crops like pennycress and winter camelina provide both environmental and potential economic resources to growers. They are cash‐generating crops able to sequester labile soil nutrients, which protects and promotes soil health from autumn through early summer. Core Ideas Alternative, easily established winter‐surviving covers are needed in the Upper Midwest. Cover crops sequestered N and reduced soil and soil water NO3−–N in autumn compared with fallow. Winter oilseed crops reduced soil water NO3−–N in autumn through soybean planting. Novel winter oilseeds provide environmental and economic incentives to enhance adoption.

Relay‐cropping of the novel oilseeds winter camelina (Camelina sativa L.) and pennycress (Thlaspi arvense L.) with short‐season crops such as soybean [Glycine max (L.) Merr.] can provide economic and environmental incentives for adopting winter cover crop practices in the U.S. Upper Midwest. However, their ability to reduce nutrient loss in surface runoff is unknown. Accordingly, surface runoff and quality were evaluated during three seasonal phases (cover, intercrop, and soybean) over 2 yr in four cover crop–soybean treatments (pennycress, winter camelina, forage radish [Raphanus sativus L.], and winter rye [Secale cereale L.]) compared with no‐till and chisel‐till fallow treatments. Runoff was collected with Gerlach troughs and assessed for concentrations and loads of NO3−–N, total mineral N, soluble reactive P (SRP), and total suspended solids (TSS). Cumulative runoff and nutrient loads were greater during the winter cover phase because of increased snow melt and freeze–thaw released nutrients from living vegetation. In contrast, cumulative TSS was greater during intercrop and soybean phases due to high‐intensity rainfall events with an open soybean canopy. Average TSS loads during the intercrop phase were reduced by 75% in pennycress compared with fallow and radish treatments. During the soybean phase, average TSS, total mineral N, and SRP loads were generally elevated in cover crop treatments compared with no‐till. Overwintering cover crops may contribute to mobility of nutrients solubilized from living or decomposing vegetation; however, this was balanced by their potential to reduce runoff and TSS during high‐intensity spring rains.