Biomass, nitrogen, and carbon loss from the novel oilseed pennycress relative to annual ryegrass and cereal rye

The rate of pennycress residue decomposition and mineralization is critical in determining potential nutrient availability for following crops. To better understand pennycress decomposition, we examined biomass, nitrogen, and carbon loss from wild pennycress, gene edited AOP2 knockout pennycress, annual ryegrass, and cereal rye. Biomass was collected from all crops at the time of cash crop planting, and 20 g of biomass was placed in individual mesh forage bags (50 +/- 10 mm). We placed 99 bags from each crop between rows of corn (n = 5) on the soil surface of the dominant soil types (SA and DR) at the ISU farm. Replicate bags were collected from each soil type over the following 84 days, weighed for biomass, and analyzed for carbon and nitrogen in the plant residue. Loss of biomass differed by crop and soil type (F = 3.7(3,32), p = 0.023) with annual ryegrass losing biomass most rapidly followed by cereal rye, wild-type pennycress, and the domesticated low glucosinolate, AOP2 knockout, pennycress. Nitrogen (F = 8.5(3,36), p < 0.0001) and carbon (F = 67.5(3,36), p < 0.0001) losses differed by crop and not soil type following a similar trend as biomass loss. Our results suggest that both wild-type and AOP2 knockout pennycress can be expected to decompose similarly to a rye cover crop but with slower nutrient loss. Pennycress has potential to act as an effective short-term nutrient sink in agroecosystems.