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Spectral Reflectance Properties of Winter Cover Crops in the Southeastern Coastal Plain

^a USDA-ARS Southeast Watershed Research Laboratory, P.O. Box 748, Tifton, GA 31794
^b Auburn Univ., Agronomy and Soils Dep., Auburn, AL, 36849
^c USDA-ARS National Soil Dynamics Lab., Auburn, AL 36832

View larger version (12K): [in this window] [in a new window]   Fig. 1. Daily precipitation (mm) 2005 (10 May–15 June) and 2006 (20 Apr.–30 May) data acquisition periods. Sampling times are denoted by arrows.

View larger version (12K): [in this window] [in a new window]   Fig. 2. Spectral response curves for the combined cover, turnip and conventional tillage fallow treatments in 2005. Black oat, rye, and clover comprise the combined cover due to lack of significant differences in spectral response (alpha = 0.05). Data represent general trends in reflectance (%) throughout the 485- to 1650-nm range.

View larger version (12K): [in this window] [in a new window]   Fig. 3. Spectral response curves for the combined cover, turnip and conventional tillage fallow treatments in 2006. Black oat, rye, and clover comprise the combined cover due to lack of significant differences in spectral response (alpha = 0.05). Data represent general trends in reflectance (%) throughout the 485- to 1650-nm range.

View larger version (27K): [in this window] [in a new window]   Fig. 4. Analysis of variance for the combined cover (black oat, rye, and clover covers), turnip, and conventional tillage fallow treatments for each remotely sensed index. Remotely sensed indices include the greenness normalized difference index (GNDVI), the normalized difference vegetation index (NDVI), and the crop residue cover index1 (CRC1). Significant interactions were observed between dates and treatments; thus, treatment differences were analyzed by date. Means followed by the same letter are not significantly different (alpha = 0.05). Dashed lines represent minimum threshold values for the crop residue cover index and distinguish between conventional and no-tillage systems.

View larger version (32K): [in this window] [in a new window]   Fig. 5. Analysis of variance showing variability in index values between sampling events for each cover treatment. Remotely sensed indices include the greenness normalized difference index (GNDVI), the normalized difference vegetation index (NDVI), and the crop residue cover index1 (CRC1). Means followed by the same letter are not significantly different (alpha = 0.05). Treatments are identified as follows: CC05 = combined cover 2005, CC06 = combined cover 2006, F05 = fallow 2005, F06 = fallow 2006, T05 = turnip 2005, and T06 = turnip 2006. The combined cover treatments are comprised of black oat, rye, and clover due to a lack of significant differences in spectral response (alpha = 0.05).