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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Hydrology and Remote Sensing Laboratory » Research » Publications at this Location » Publication #332938
Title: Topographic and physicochemical controls on soil denitrification in prior converted croplands located on the Delmarva Peninsula, USA

Author
item LI, X. - University Of Maryland
item McCarty, Gregory
item LANG, M.W. - Fisheries & Wildlife
item Ducey, Thomas
item Hunt, Patrick
item Miller, Jarrod

Submitted to: Biogeochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/1/2017
Publication Date: 2/15/2018
Citation: Li, X., McCarty, G.W., Lang, M., Ducey, T.F., Hunt, P.G., Miller, J.O. 2018. Topographic and physicochemical controls on soil denitrification in prior converted croplands located on the Delmarva Peninsula, USA. Biogeochemistry. 309:41-49. https://doi.org/10.1016/j.geoderma.2017.09.003.
DOI: https://doi.org/10.1016/j.geoderma.2017.09.003

Interpretive Summary: Denitrification is the primary process supporting agricultural nitrate removal before it impacts water quality. Under anaerobic conditions, nitrate is typically reduced to nitrogen gases which are emitted to the atmosphere and this process is generally affected by three controlling factors, including oxygen, NO3- , and organic carbon levels. In this study, we measured denitrification potential in soils located at different landscape positions to quantify the effects of soil physicochemical characteristics and topographic metrics on the potential and capacity for nitrate removal in three agricultural production fields containing prior converted croplands on the Delmarva Peninsula. We found that topography explained the greatest amount of variation in denitrification potential across the three sites. The relationship between topography and this potential may partly be explained through the relatively robust relationship between topography and soil moisture, texture, and carbon content. Results of this study suggest that the spatial-temporal variations in denitrification at these croplands were primarily caused by complex interactions between soil properties and landscape position. Topographic metrics derived from Light Detection and Ranging data have the potential to improve understanding of denitrification variability at the landscape scale. The improved information on denitrification at field and landscape scales will advance implementation of precision agriculture technologies for minimizing impacts crop production on water quality.

Technical Abstract: Topography and soil physiochemical characteristics exert substantial controls on denitrification, and the effect of these controls is especially evident in fertilized agricultural lands. To depict these controls at a landscape scale for decision support applications, metrics (i.e., proxies) must be developed based on commonly available geospatial data. In this study, we analyzed the combined effects of eleven topographic and physiochemical factors on denitrification potential (DP) and capacity (DC) in three actively farmed crop fields that were converted from forested wetlands (i.e., prior converted croplands). Nitrate and carbon addition led to a doubling in DP compared to DC. Topography explained the greatest amount of variation in DP across the three sites. The relationship between topography and DP may partly be explained through the relatively robust relationship between topography and soil moisture, texture, and carbon content. Soil electrical conductivity (EC) exhibited the highest correlation with DC (r2 = 35%). DP and DC were higher under drought conditions with low soil moisture, relative to average conditions with relatively higher soil moisture, which may be related to the substantial increase in soil EC under drought conditions. However, DP and DC were less responsive to soil EC at sandy sites that tended to have low soil moisture. Results of this study suggest that the spatial-temporal variations in denitrification at these croplands were primarily caused by complex interactions between soil properties and landscape position. Topographic metrics derived from Light Detection and Ranging data have the potential to improve understanding of denitrification variability at the landscape scale.