Herbaceous perennial biomass production on frequently saturated marginal soils: Influence on N2O emissions and shallow groundwater.

Authors: RAU, BENJAMIN - Forest Service (FS); Adler, Paul; Dell, Curtis; SAHA, DEBASISH - Pennsylvania State University; KEMANIAN, ARMEN - Pennsylvania State University

Submitted to: Biomass and Bioenergy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/21/2019
Publication Date: 1/7/2019
Citation: Rau, B.M., Adler, P.R., Dell, C.J., Saha, D., Kemanian, A. 2019. Herbaceous perennial biomass production on frequently saturated marginal soils: Influence on N2O emissions and shallow groundwater. Biomass and Bioenergy. 122:90-98. https://doi.org/10.1016/j.biombioe.2019.01.023.
DOI: https://doi.org/10.1016/j.biombioe.2019.01.023

Interpretive Summary: There is interest is growing bioenergy crops such as perennial grasses on marginal lands including those functioning as surface water buffers, however it’s not known if increased management will reduce their water quality benefits. We measured nitrous oxide emissions and nitrate leaching across a small watershed with variable soil moisture. We found that although nitrous oxide emissions and nitrate leaching increased with nitrogen addition through fertilizer and manure, without additional nitrogen, switchgrass yields were similar and miscanthus yields were about 80% higher compared to when nitrogen fertilizer was applied to switchgrass. Perennial grasses may not need additional fertilizer in buffer strips to maintain yields while achieving water quality benefits.

Technical Abstract: Warm season perennial grasses grown for biomass have been suggested as alternative cropping systems on marginal soils to increase farm profit, reduce nitrous oxide (N2O) emissions, and improve water quality. The objectives of this study were to determine: 1) how warm season perennial grasses, switchgrass (Panicum virgatum) and Miscanthus (Miscanthus giganteus), compare to cool season grasses as streamside buffers on poorly drained marginal soils, 2) if inorganic or organic nutrient additions improve biomass yield and affect environmental outcomes, and 3) which soil variables influence N2O emissions in situ. We measured soil N2O emissions, soil solution nitrate (NO3-), ammonium (NH4+), O2, moisture, and temperature, along with shallow groundwater NH4+, NO3-, and ortho-phosphate during two growing seasons (2012-2013). N2O emissions were similar across unfertilized warm season grasses and cool season grasses. However, when switchgrass was fertilized with ammonium sulfate or broiler manure, N2O emissions increased significantly. N2O emissions were weakly correlated with soil solution NO3- concentrations and water filled pore space. Shallow groundwater N was elevated under switchgrass fertilized with ammonium sulfate, broiler manure, and when grown with the legume (Desmodium canadense) when compared to unfertilized switchgrass, Miscanthus, and cool season grasses. In 2013 dry aboveground biomass production did not differ among switchgrass treatments and average 10 Mg ha. Biomass production was significantly higher for Miscanthus (18.5 Mg ha). The results indicate that unfertilized switchgrass and Miscanthus are as effective as cool season grasses at mitigating N2O emissions and improving water quality, and that Miscanthus has potential production advantages over switchgrass grown on frequently saturated soils.