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Title: Use of Field-based Near Infrared Sensors to Map Soil Carbon in Agricultural Ecosystems

Author
item McCarty, Gregory
item Hively, Wells - Dean
item Reeves Iii, James
item LUND, ERIC - VERIS TECHNOLOGIES

Submitted to: Australian Grains Research and Development Corporation Cropping Research Updates
Publication Type: Proceedings
Publication Acceptance Date: 2/19/2008
Publication Date: 2/19/2008
Citation: McCarty, G.W., Hively, W.D., Reeves, J.B., Lund, E. 2008. Use of field-based near infrared sensors to map soil carbon in agricultural ecosystems. In: Proceedings of the 1st Global Workshop on High Resolution Digital Soil Sensing and Mapping, February 5-8, 2008, Sydney, Australia. 2:17.

Interpretive Summary: Increasing carbon dioxide content of the Earth’s atmosphere has stimulated research to assess the role of terrestrial ecosystems in the global carbon cycle. The terrestrial biosphere is an important component of global carbon budget, but estimates of carbon sequestration in soil is limited by the ability accurately measure stored soil carbon. Agricultural croplands have a great potential for sequestering atmospheric carbon dioxide if carbon-positive farming methods such as no-till, organic, and perennial cropping are adopted, but current technologies for monitoring soil carbon are not cost effective, or they depend on laborious methods. Near infrared spectroscopy (NIR) offers a rapid means for measurement of soil C based on the reflectance spectra of illuminated soil. We evaluated two field based NIR spectral sensors (airborne- and tillage-based) covering for soil carbon detection and compared them to laboratory methods. We intensively soil sampled five tilled agricultural fields. The test fields were located on the Delmarva Peninsula in Maryland. The information quality of data from the two field sensors were comparable the to laboratory-acquired data indicating that these field-based NIR sensors performed well for generating spatial data. These new spectral methods for detecting soil carbon should increase the efficiency of measuring carbon stocks within agricultural systems.

Technical Abstract: Ability to detect changes in soil carbon storage is an important component of verifying sequestration of soil carbon within agricultural ecosystems. Rapid methods of measuring soil carbon such as near infrared spectroscopy have gained considerable interest but problems in accurate measurement still persists resulting from the high spatial variability of soil carbon within agricultural landscapes. Tillage-based and airborne-based NIR sensors offer opportunity to effectively capture the spatial structure of soil carbon within agricultural landscapes. We evaluated an airborne spectral sensor covering the range from 450 to 2450 nm at 3-m spatial resolution and a tillage sensor covering the range from 920 to 1718 nm. We intensively soil sampled five tilled agricultural fields within the flight path of the airborne sensor. The test fields were located on the Delmarva Peninsula in Maryland, USA. The information quality of spectral data acquired by these field sensors were compared to laboratory-acquired spectral data of soil samples taken at 304 geo-referenced locations within the fields. The Partial Least Squared (PLS) regression models developed from all three spectral data sources were very comparable, indicating that these two field-based NIR sensors performed well for generating spatial data. Such methods will permit better assessment of soil carbon sequestration in agricultural ecosystems by use of improved landscape models that account for biogeochemical and soil redistribution processes that occur within often complex topographic and management settings.