ARS | Publication request: Effects of Decomposition on Remotely Sensed Estimates of Wheat Residue Cover

Submitted to: Remote Sensing
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 21, 2010
Publication Date: January 27, 2010
Citation: Daughtry, C.S., Serbin, G., Reeves, J.B., Doraiswamy, P.C., Hunt, E.R. 2010. Effects of decomposition on remotely sensed estimates of wheat residue cover. Remote Sensing. 2:416-431.

Interpretive Summary: Crop residues or plant litter is the portion of a crop left in the field after harvest. Management of crop residues is an integral part of most conservation tillage systems. Crop residues on the soil surface provide a protective barrier against water and wind. Soil tillage and residue harvesting for bio-energy are management practices that reduce crop residue cover. As the chemical and physical properties of crop residues change during decomposition, their spectral reflectance properties also change which affects the ability of remote sensing methods to assess residue cover. We measured and modeled the changes in wheat straw fiber composition and spectral reflectance during decomposition and assessed the impact of these changes on remotely sensed estimates of residue cover. These results indicate that current broad-band, multispectral imaging systems will not provide robust estimates of crop residue cover when soils and residues are variable. Advanced multispectral sensors with multiple, relatively narrow shortwave infrared bands or hyperspectral sensors are needed to assess crop residue cover reliably over diverse agricultural.

Technical Abstract: Quantification of crop residue cover is required to assess the extent of conservation tillage. Our objectives were to measure the changes in wheat straw composition and spectral reflectance during decomposition and to assess impact of these changes on remotely sensed estimates of residue cover. Mesh bags filled with wheat straw were placed on the soil surface and removed at intervals over 22 months. The relative proportions of cellulose and hemi-cellulose in the straw declined while lignin increased. Reflectance spectra of wheat straw and three soils were measured over 350-2500 nm region. Absorption features in the reflectance spectra associated with cellulose diminished as the straw decomposed. Scenes with mixtures of soil and residues were simulated. The Cellulose Absorption Index (CAI) was a robust estimator of crop residue cover. Advanced multi-spectral sensors with multiple relatively narrow shortwave infrared bands or hyperspectral sensors are needed to assess crop residue cover reliably over diverse agricultural landscapes.