Soybean Seed Yield and Quality as a Response to Field Pennycress Residue

Field pennycress (Thlaspi arvense L.; hereafter pennycress) is an oilseed crop being investigated as an off-season biofuel source that can potentially fit into the existing crop rotation cycle with soybean [Glycine max (L.) Merr.]. The objective of this 2-yr study was to evaluate the effect of pennycress residue on seed yield and quality components of soybean planted during five consecutive weeks, from mid-May to mid-June. In 2009 and 2010, the mean soybean dry weight seed yield after pennycress residue for all planting dates (4108 and 3490 kg ha(-1), respectively) was greater than yield from fallow control plots (3636 and 2992 kg ha(-1), respectively). However, in 2010, soybean planted after pennycress had slightly lower oil content (202 g kg(-1)) than that obtained from fallow control plots (207 g kg(-1)) (P < 0.01). Delayed planting until mid-June resulted in lower population density, plant height, seed yield, and oil concentration. Before June, planting date had no significant influence on soybean seed yield and quality. Protein content in soybean seed was not affected by year, pennycress residue, or planting date. Variation in the experimental year temperature values led to significant changes in oil components. High temperatures decreased levels of linoleic, linolenic, and stearic acids but increased levels of palmitic and oleic acids. Overall, pennycress had no negative effect on the subsequent soybean crop.