Reduced Potential for Nitrogen Loss in Cover Crop–Soybean Relay Systems in a Cold Climate

Abstract

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.

Establishing winter annual cover crops by interseeding into Maize and Soybean

“…() for a maize system experiment conducted in South Dakota. In addition, PC and WC biomass were lower than previous findings where these oilseeds were direct seeded after spring wheat (Weyers et al., ).…”

Soil Nitrogen in Response to Interseeded Cover Crops in Maize–Soybean Production Systems

“…Prior to seeding both maize and soybean, spring tillage was performed (type of tillage and depth varied by location). Detailed management practices used are described in a previous publication [29]. In brief, WC, PC, and WR were broadcast interseeded at 1368, 1064, and 222 pure live seeds (PLS) m −2 .…”

“…Successful establishment of PC and WC as covers following short-season small grains, and the ecosystem services they offer is well documented [29]. However, establishment of these oilseeds following maize or soybean grain harvest in the upper Midwest latitude is problematic because of the short period between harvest and winter freezing [30][31][32].…”

Genetic Diversity of Field Pennycress (Thlaspi arvense) Reveals Untapped Variability and Paths Toward Selection for Domestication

“…Pennycress is extremely winter hardy in natural settings (−30 • C) [6], therefore, the species is an excellent candidate for a fall planted cover crop. It provides a protective soil cover over the winter and spring, and reduces soil erosion and nutrient loss, while also suppressing spring weed growth [4,5,7]. In addition, it acts as a food source for pollinators in the early spring [8].…”