Yield tradeoffs and nitrogen between pennycress, camelina, and soybean in relay- and double-crop systems

To gain additional value from land during winter fallow periods in corn (Zea mays L.)–soybean [(Glycine max (L.) Merr.] rotations, growers in the Upper Midwest are considering winter annual oilseed crops such as field pennycress (Thlaspi arvense L.) and winter camelina [Camelina sativa (L.) Crantz]. The objective of this study was to (i) explore trade-offs between soybean and winter oilseed crop yield as influenced by timing of winter oilseed crop harvest and of soybean planting, and (ii) evaluate how inorganic soil N was affected by the presence or absence of pennycress or camelina. Field experiments were conducted at three sites in Minnesota to evaluate yield of field pennycress and camelina winter oilseed crops planted in a double-crop system or planted early or late in a relay-cropping system. Soybean grain yield was reduced in one of the three sites in 2014 and at all sites in 2015. However, the addition of a winter oilseed crop in a relay- or double-crop system increased the total oilseed production. The optimal cropping strategy for achieving maximum total oilseed crop yield was dependent on environment. Winter oilseed crop yield tended to be greatest when harvested late rather than early in either a relay- or double-crop system. Pennycress and camelina significantly reduced inorganic soil N along the entire soil profile compared to soybean alone, especially in the spring (53–72%) and autumn (18–19%) when the potential for N loss is greatest. Pennycress and camelina, when integrated with soybean in a late-planted relay- or double-crop system, increased total crop yield while providing critical ecosystem services.