Assessing Soil Tillage Intensity Using Remote Sensing.

Quantification of crop residue cover is required to evaluate the effectiveness and extent of conservation tillage practices.  The standard technique for measuring crop residue cover, line-point transect, is impractical for monitoring many fields in a timely manner.  Multispectral remote sensing approaches for estimating crop residue cover have had mixed success because crop residues and soils are spectrally similar in the broad spectral bands of most current remote sensing systems.  Robust alternative approaches are based on detecting cellulose and lignin absorption features in crop residues.  These features are evident in reflectance spectra of crop residues, but not in spectra of soils.  

Our objectives were to assess crop residue cover and soil tillage intensity using remotely sensed data.  We measured crop residue cover using line-point transect and photographic methods in corn and soybean fields shortly after most of the crops had been planted.  Advanced multispectral images were acquired for test sites in Maryland and Iowa.  Spectral indices were calibrated with a portion of the measured crop residue cover data and validated with the remaining data.  Alternative, less labor-intensive sampling schemes for acquiring surface reference data were evaluated.  Classification accuracy was not significantly degraded by the alternative sampling schemes.