|DAVIS, BRIAN - University Of Maryland|
|NEEDELMAN, BRIAN - University Of Maryland|
|YARWOOD, STEPHANIE - University Of Maryland|
Submitted to: Agriculture Ecosystems and the Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/24/2018
Publication Date: 12/1/2018
Citation: Davis, B.W., Mirsky, S.B., Needelman, B.A., Cavigelli, M.A., Yarwood, S.A. 2018. Nitrous oxide emissions increase exponentially with N rate from cover crops and poultry litter. Agriculture Ecosystems and the Environment. 272:165-174. https://doi.org/10.1016/j.agee.2018.10.023.
Interpretive Summary: Nitrous oxide (N2O) is a potent greenhouse gas, with 298 times the warming effect of CO2. The major source of N2O is agricultural soils, and emissions are associated with high soil nitrogen and moisture. Cover crops are nonmarket crops that can be used to build soil health for the following cash crop, but have the potential to increase the N and moisture conditions that cause N2O emissions. Banding animal manure below the soil surface is beneficial for reducing phosphorus erosion and N volatilization, but could also lead to increased N2O emissions. To evaluate the impact of these two components of sustainable agricultural systems on N2O emissions, we conducted a three year field experiment with no-till corn (Zea mays L.) following cover crops fertilized with subsurface-banded poultry litter (PL). The cover crops used were cereal rye (Secale cereale L.), hairy vetch (Vicia villosa Roth), and a cereal rye:hairy vetch mixture (60%:40%), compared to bare ground. Four rates of subsurface-banded PL were applied: 9, 76, 144, and 278 kg plant-available N ha-1. Emissions of N2O increased exponentially with total N rate under all the cover crop treatments, and emissions were highest following hairy vetch and lowest following cereal rye. The cereal rye:hairy vetch mixture did not affect N2O emissions compared to bare ground. Additionally, there were comparisons with application method and a mineral fertilizer. Tillage-incorporated poultry litter decreased N2O emissions following hairy vetch and the mixture relative to subsurface-banded poultry litter but had no effect following bare ground or cereal rye. The mineral fertilizer decreased emissions relative to subsurface-banded PL in the bare ground treatment, but increased emissions over subsurface-banded PL in the cereal rye:hairy vetch mixture; there was no difference following cereal rye or hairy vetch. This work establishes a functional relationship between N2O emissions and N inputs from multiple organic sources. We also show that adopting grass cover crops and grass:legume mixtures does not increase N2O emissions. The results of this work will be used by researchers and policy makers in assessing the implications of cover crop and animal byproducrs on greenhouse gas emmisions.
Technical Abstract: Use of cover crops in no-till systems can provide plant-available nitrogen (N) and increase soil moisture for the following cash crop, but excess N and moisture have the potential to increase emissions of nitrous oxide (N2O), a potent greenhouse gas. Subsurface application of animal manures reduces phosphorus erosion and N volatilization losses, but creates concentrated hotspots of N below the surface, where soils remain moist longer. Our objectives were to determine the effects of cover crop residue type and pelletized poultry litter (PL) rate and application method on soil N2O emissions at the field scale during the corn (Zea mays L.) growing season and following winter and spring for three years. We tested effects on three types of cover crop residue: cereal rye (Secale cereale L.), hairy vetch (Vicia villosa Roth), and a cereal rye:hairy vetch mixture (60%:40%), compared to bare ground. Four rates of subsurface-banded PL were applied: 9, 76, 144, and 278 kg plant-available N ha-1. A comparison of subsurface-banded PL and tillage-incorporated PL (67 kg plant-available N ha-1) was made, as well as subsurface-banded PL and surface-banded urea-ammonium nitrate mineral fertilizer (UAN; 150 kg N ha-1). For all cover crop treatments, N2O emissions increased exponentially with total N input rate (PL+cover crop residue). The cereal rye:hairy vetch mixture had no effect on N2O emissions when compared with bare ground, while the cereal rye decreased emissions and hairy vetch increased emissions. Tillage-incorporated PL decreased N2O emissions following hairy vetch and the mixture relative to subsurface-banded PL (by 3.06 and 1.82 kg N2O-N ha 1 y-1), but had no effect following bare ground or cereal rye. UAN decreased emissions relative to subsurface-banded PL in the bare ground treatment by 1.66 kg N2O-N ha 1, but UAN increased emissions over subsurface-banded PL by 3.71 kg N2O-N ha 1 in the cereal rye:hairy vetch mixture; there was no difference following cereal rye or hairy vetch.