Influence of Harvest Date on Pennycress Seed Yield and Quality.

Field pennycress (Thlaspi arvense L.) is a short-life cycle, winter-hardy, oilseed crop slated for sustainable intensification in Upper Midwest corn and soybean cropping systems. Pennycress can increase the profitability of the corn and soybean cropping systems through oilseed production while providing needed soil cover to address soil and water quality issues emerging from uncovered soil surfaces during winter season. Even though pennycress shows great promise as a new winter annual crop, identification of optimal harvest timing is needed to minimize harvest loss through seed shatter, while maximizing oilseed yield and quality. Pennycress was harvested at eight different dates ranging from early to late June. Pennycress phenology, seed yield and quality, and canopy reflectance indices (NDVI and LAI) associated with harvest time were evaluated. Seed moisture, LAI, and NDVI all decreased significantly (P < 0.05) as harvesting date progressed. Biomass was significantly higher (4066 kg ha^-1) at fourth harvest date than the last three harvest dates (2280-2740 kg ha^-1). Maximum oil content (33%) also occurred by the fourth harvest date (mid June) and did not differ significantly with later harvest dates. Seed yield was highest (1348 kg ha^-1) at the fourth harvest date but declined significantly with later (sixth-eighth) harvest dates (357-881 kg ha^-1) due to seed shattering loss. These results depict that to maximize the seed yield and oil content in pennycress, the best harvest time should be near mid-June to reduce yield-loss through shattering, and allow for earliest planting of double-cropped soybean. However, seed moisture corresponding to optimum yield was too high (46-66%) at this time. Therefore, future research will focus on two activities: (1) use of desiccants to reduce the seed moisture content, and (2) breeding for reduced seed-shattering varieties. These foci will maximize the economic and environmental benefits of pennycress in double cropping systems.