Economics and agronomics of relay-cropping pennycress and camelina with soybean in Minnesota

Authors: OTT, MATTHEW - University Of Minnesota; EBERLE, CARRIE - University Of Wyoming; THOM, MATTHEW - University Of Minnesota; Archer, David; Forcella, Frank; Gesch, Russell - Russ; WYSE, DONALD - University Of Minnesota

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/18/2019
Publication Date: 4/18/2019
Publication URL: https://handle.nal.usda.gov/10113/6480382
Citation: Ott, M.A., Eberle, C.A., Thom, M.D., Archer, D.W., Forcella, F., Gesch, R.W., Wyse, D.L. 2019. Economics and agronomics of relay-cropping pennycress and camelina with soybean in Minnesota. Agronomy Journal. 111:1281-1292. https://doi.org/10.2134/agronj2018.04.0277.
DOI: https://doi.org/10.2134/agronj2018.04.0277

Interpretive Summary: The winter-hardy oilseed cover crops, winter camelina and pennycress, were double-cropped with soybean. The double-cropping system is known as relay-cropping, wherein the cover crops are sown in autumn and the soybean is drilled into the living cover crop in early May. The cover crops are harvested in late June over the soybean canopy. The soybean subsequently is harvested at the usual time in September. In our experiments radish and winter rye served as traditional cover crop comparisons, and mono-cropped soybean in both tilled and no-till situations served as conventional comparisons. The experiments were performed during 2014-15 and 2015-16 at three sites spanning the north-south gradient of Minnesota. Seed yields were measured and net financial returns were estimated. Total double-crop seed yields (oilseed + soybean) typically equaled or exceeded those of mono-cropped soybean and soybean with traditional cover crops, except when June rainfall was exceptionally low, which caused crop-crop competition between the oilseeds and soybean. Net incomes for double-crop systems generally were similar to those of mono-cropped soybean and soybean with traditional cover crops. The financial equivalence of these cropping strategies is important because double-cropping also provides important agro-ecosystem services not seen in mono-cropped soybean. These services cannot be valued easily in an economic sense, but include sequestration of soil nitrates, protection from soil erosion, provision of forages for pollinators, etc. Thus, if growers precede their soybean crops with winter camelina or pennycress, they likely will gain many environmental benefits and not lose money. These results will be of interest to growers, crop advisors, conservationists, land use regulators, and green products industries.

Technical Abstract: Cover crops can reduce water pollution caused by NO3-N, 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-soybean 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.) autumn-planted into spring wheat stubble. The fallow treatments consisted of no-tilled and conventionally tilled soil. Radish winter killed and rye was terminated chemically before planting soybean in early May. Soybean (Glycine max L.) 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 kg ha-1 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 light-stress, which likely reduced soybean yield in these treatments. Soybean yields within the oilseed treatments ranged from 66% to 79% of those within fallow treatments. When oilseed and inter-seeded soybean yields were combined, total seed yields generally were equal to or exceeded those of mono-cropped soybean. Also, net income for inter-seeded systems was typically equivalent to mono-cropped soybean. Improvements in net returns are likely needed before the agroecosystem benefits of oilseed cover crops are fully realized.