Economics and Agronomics of Relay‐Cropping Pennycress and Camelina with Soybean in Minnesota

Abstract

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.

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

“…Potential benefits of cover crops do need to be evaluated against potential liabilities. Although autumn sequestration of N by winter rye and radish was pronounced, neither treatment indicated positive or negative effects, as soybean yields in these treatments were not statistically different than yields under fallow treatments (Ott et al, 2018). This indicates that neither sequestration, immobilization with decaying biomass, nor potential loss of nutrients from the system were of consequence in winter rye or radish.…”

“…This indicates that neither sequestration, immobilization with decaying biomass, nor potential loss of nutrients from the system were of consequence in winter rye or radish. However, double‐cropping oilseeds with soybean did cause a delay in soybean growth, and a reduction in soybean yields (Ott et al, 2018). On the other hand, the total production of both crops, particularly for oil content, can exceed that of monoculture soybeans, which might provide an economic incentive for adoption (Gesch et al, 2014; Berti et al, 2015; Ott et al, 2018).…”

“…However, double‐cropping oilseeds with soybean did cause a delay in soybean growth, and a reduction in soybean yields (Ott et al, 2018). On the other hand, the total production of both crops, particularly for oil content, can exceed that of monoculture soybeans, which might provide an economic incentive for adoption (Gesch et al, 2014; Berti et al, 2015; Ott et al, 2018). This combination of economic viability, environmental benefits such as floral resources for pollinators (Eberle et al, 2015; Thom et al, 2018), and the potential to reduce nutrient loss, which was established by N and P uptake and soil and soil‐water dynamics in the current study, indicates that autumn‐seeded, overwintering oilseed crops can provide an opportunity to increase cropping system diversity and improve economic and environmental outcomes.…”

The hidden land use cost of upscaling cover crops

“…Our results suggest that cover crop breeding research should shift to emphasize increased seed yield. Only a handful of cover crops are actively being bred for seed productivity (i.e., Pennycress and Camelina; [17]). Most breeding has focused on ecosystem service values [9] and forage quality [11], with seed yields holding little to no priority.…”

Translational genomics using Arabidopsis as a model enables the characterization of pennycress genes through forward and reverse genetics

“…Pennycress grown as a cover can reduce nutrient leaching and soil erosion and reduce the growth of spring weeds (Johnson et al ., ; Thom et al ., ). In addition, as an oilseed, pennycress holds great promise as a new cover crop that can provide an economic return to rural communities (Ott et al ., ).…”