IMPROVING WATER QUALITY THROUGH REDUCING AGRICULTURAL NUTRIENT LOSS: FIELD PENNYCRESS AS A COVER CROP

Agricultural nutrient loss through water runoff from the Upper Mississippi (UM) River Basin is one of the major contributing sources to the Gulf of Mexico hypoxic dead zone. To combat the growing dead zone, Illinois is collaborating with regulatory agencies to develop a comprehensive strategy to reduce nutrient loss from agricultural fields. Cover cropping has been identified as one strategy for farmers to use to reduce nutrient loss from their fields and improve soil quality at the same time. However, the high cost and slow economic return rate of implementing cover crops prevent farmers from adopting traditional cover crops.

Field pennycress (Thlaspi arvense) is an emerging potential “cash cover crop” species that may provide the benefits of traditional cover crops and the economic incentive (biofuel potential) farmers need to widely implement cover cropping in their fields. However, the effectiveness of pennycress at reducing nutrient loss compared to traditional cover crop species still needs to be determined. To investigate pennycress’ potential as a cover crop, we designed a replicate plot experiment in central Illinois active farm fields. Three sets of replicate plots at 2 acres/plot will receive three separate treatments following cash crop: reference plots with no field pennycress, field pennycress plots, and field pennycress plots with additional nitrogen fertilizer (Pennycress + N). Each plot also has its own tile drainage to imitate midwestern farming practice. Field pennycress is planted following cash crop harvest in early fall and grows throughout late fall to late spring next year. To assess the nutrient concentration change in the plots we use field lysimeters to measure soil pore water nutrient concentrations during peak pennycress growth season (mid to late spring) to observe the effects of pennycress on soil and soil porewater nutrients. Initial results from spring’ 20 show soil nitrates decreased in plots with pennycress presence, but soil pore water had higher concentration in plots with pennycress and pennycress + N. While preliminary result contradicts our hypothesis of pennycress’s ability to reduce soil and soil porewater nitrate, additional sampling would occur for spring’21 to observe whether the effect seen in spring’20 is conclusive or an anomaly due to field condition variability.