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ARS Home » Southeast Area » Tifton, Georgia » Southeast Watershed Research » Research » Publications at this Location » Publication #203929
Title: Spectral Reflectance Properties of Winter Cover Crops in the Southeastern Coastal Plain

Author
item Sullivan, Dana
item SHAW, J - AUBURN UNIV
item Price, Andrew
item VAN SANTEN, E - AUBURN, AL

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/19/2007
Publication Date: 11/1/2007
Citation: Sullivan, D.G., Shaw, J.N., Price, A.J., Van Santen, E. 2007. Spectral Reflectance Properties of Winter Cover Crops in the Southeastern Coastal Plain. Agronomy Journal. 99:1589-1596.

Interpretive Summary: Reduce tillage and residue management can have significant impacts to soil and water quality, primarily through the accumulation of soil organic carbon. Yet, current methods of tillage and crop residue cover assessment are inappropriate for watershed scale determinations. This study was designed to compare spectral reflectance patterns of four alternative winter cover crops and evaluate a remotely derived index for differentiating between conventional and conservation tillage systems. Remotely sensed data were acquired in the visible and near-infrared the light spectrum using a handheld spectroradiometer. Ground truth data include digital images, soil water content, and residue carbon content. Results showed that rye, clover, and black oat were spectrally similar, and less reflective compared to conventional tillage, fallow treatments. All remotely sensed indices successfully differentiated between conventional and no-tillage systems, but the crop residue cover index was least sensitive to variability in canopy contributions and soil water content. Using the crop residue cover index, a threshold value of > 0.59 can be used to identify conservation tillage treatments when the normalized difference vegetation index is < 0.42

Technical Abstract: Conservation tillage is a commonly adopted best management practice for reducing runoff and erosion, and increasing infiltration. Yet current methodologies in place to monitor conservation tillage adoption are time and resource intensive, and largely inappropriate for regional or national assessments. A major goal of this study was to evaluate the spectral response properties of four alternative winter cover crops as well as a remotely derived crop residue cover index as a tool for rapidly differentiating between tillage systems. Experimental plots were located at the Field Crops Unit, E.V. Smith Extension Center of the Alabama Agricultural Experiment Station. Treatments consisted of one fallow conventional tillage treatment and four no-tillage treatments with the following winter covers: black oat (Avena strigosa Schreb.), crimson clover (Trifolium incarnatum L.), turnip (Brassica rapa L. subsp.rapa), or rye (Secale cereale L.). Remotely sensed data were acquired three times prior to canopy closure, using a handheld multispectral radiometer (485 –1,650 nm) in 2005 and 2006. Coincident with remotely sensed data collection, digital images were acquired for residue cover classification and line-transect assessments. Soil water content was also measured to assess the impact of changes in soil background reflectance on crop residue assessments. Results showed that rye, clover, and black oat were spectrally similar, and less reflective compared to conventional tillage, fallow treatments. All remotely sensed indices successfully differentiated between conventional and no-tillage systems, but the crop residue cover index was least sensitive to variability in canopy contributions and soil water content. Using the crop residue cover index, a threshold value of > 0.59 can be used to identify conservation tillage treatments when the normalized difference vegetation index is < 0.42.