Evaluating the relationship between biomass, percent groundcover and remote sensing indices across six winter cover crop fields in Maryland

Authors: PRABHAKARA, K. - University Of Maryland; HIVELY, DEAN, W. - Us Geological Survey (USGS); McCarty, Gregory

Submitted to: International Journal of Applied Earth Observation and Geoinformation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2015
Publication Date: 7/15/2015
Citation: Prabhakara, K., Hively, D., Mccarty, G.W. 2015. Evaluating the relationship between biomass, percent groundcover and remote sensing indices across six winter cover crop fields in Maryland. International Journal of Applied Earth Observation and Geoinformation. 39:88-102.

Interpretive Summary: Planting cover crops is an effective method to reduce both nitrogen leaching and sedimentation into waterways. Winter cover crops are planted post-harvest on corn and soybean fields to scavenge residual nitrogen that remains in the soil, and to meet soil erosion guidelines, providing positive water quality benefits. Typical winter cover crop practices include use of small grains that are tolerant of winter conditions. Cover crops accumulate biomass during the fall, with growth slowing through the winter and typically green up again in the spring. Earlier planted crops are able to accumulate more biomass prior to the onset of cold weather. Other factors, including species, and the amount of residual nitrogen available from the previous crop can lead to a large range of aboveground biomass across the landscape. As increased aboveground biomass of cover crops is related to greater nutrient uptake and more groundcover, it is important to be able to accurately estimate cover crop biomass. Remote sensing measurements that measure greenness are often used to estimate aboveground biomass. Additionally, remote sensing indices derived from near-infrared and visible bands can be correlated with vegetative groundcover and are used for measuring percent groundcover. More groundcover is associated with reduced erosion. A majority of sun light in the visible spectrum is absorbed by pigments in the leaves, resulting in low reflectance, especially in the red portion of the spectrum with slightly higher reflectance in the green wavelengths. Vegetation also reflects brightly in the near-infrared region. These properties can be used to produce robust vegetation indices based on reflected light. This study compared the ability of different vegetation indices to detect performance of winter cover crops. Additionally, the relationship between percent groundcover and aboveground biomass were compared, as well as how both variables related to accumulated growing degree days.

Technical Abstract: Planting cover crops is an effective method to reduce both nitrogen leaching and sedimentation into waterways. Winter cover crops are planted post-harvest on corn and soybean fields to scavenge residual nitrogen that remains in the soil, and to meet soil erosion guidelines, providing positive water quality benefits. Typical winter cover crop practices include use of small grains tolerant of winter conditions. Cover crops accumulate biomass during the fall, with growth slowing through the winter and typically green up again in the spring. Earlier planted crops are able to accumulate more biomass prior to the onset of cold weather. Other factors, including species, and the amount of residual nitrogen available from the previous crop can lead to a large range of aboveground biomass across the landscape. As increased aboveground biomass of cover crops is related to greater nutrient uptake and more groundcover, it is important to be able to accurately estimate cover crop biomass. Remote sensing measurements that measure greenness are often used to estimate aboveground biomass. Additionally, remote sensing indices derived from near-infrared and visible bands can be correlated with vegetative groundcover and are used for measuring percent groundcover. A majority of sun light in the visible spectrum is absorbed by pigments in the leaves, resulting in low transmittance and reflectance, especially in the red portion of the spectrum with slightly higher reflectance in the green wavelengths. Vegetation also reflects brightly in the near-infrared region. These properties can be used to produce robust indices of vegetation based on reflected light. This study compared the ability of different vegetation indices to detect growth performance of winter cover crops.