Harvest attributes and seed quality predict physiological maturity of pennycress

In the Upper Midwest, corn (Zea mays L.) and soybean (Glycine max [L.] Merr.) dominate the landscape, but only for six to seven months of the year. Thus, opportunities exist to establish crops that can utilize the remainder of the growing season and contribute to overall farm profitability. One species of interest is pennycress (Thlaspi arvense L.), but a lack of established agronomic best management practices is a barrier to successful crop production. The objectives of this study were to identify a range of cumulative growing degree days (CGDD) corresponding to pennycress physiological maturity, determine the optimal harvest window that maximizes pennycress seed yield and oil content, and characterize changes in pennycress seed attributes over seed maturation. This study was conducted over the 2016–2017 and 2017–2018 growing seasons with ‘MN106’ pennycress at two locations in Minnesota, USA. Seed dry weight stabilized within the window of maximum seed yield, but oil content did not maximize until after this period. However, there was minimal loss of oil content when pennycress was harvested within the seed yield maximization window. Based on these parameters, as well as seed moisture, it was estimated that pennycress reached physiological maturity between 2230 and 2250 °C d CGDD, or about a week prior to harvest maturity in terms of crop phenology. Delaying harvest to harvest maturity resulted in a 26% loss in harvestable seed due to seed shatter compared with the average maximum seed yield of 928 kg ha−1. Ensuring maximum pennycress seed yield and oil content at harvest is imperative to successful production and contribution to farm economic viability. •Parameters indicating pennycress physiological maturity maximized in a similar order, regardless of site-year.•Pennycress reached physiological maturity between 2230 and 2250 °C CGDD.•Seed moisture was too high at physiological maturity for mechanical harvest, so moisture reduction will be necessary to facilitate the earliest possible pennycress harvest.