Spectral Evaluation of the Conservation and Conventional Tillage Systems under Rainfed Condition

Differences between spectral reflectance can be the base of identification of crop residue rate and crop growth by remote sensing. A 2-year experiment was conducted under dryland conditions to determine the crop residue retained on soil surface in conservation and conventional tillage systems. Tillage treatments comprised of conventional tillage (MD: mouldboard plough + disk)، reduced tillage (CH: chisel plough + disk)، minimum till (MT: Stubble cultivator)، and no-till (NT1 and NT2: with standing stubble and total residue، respectively). Remotely sensed data of crop residue and plant growth were acquired، using a handheld multispectral radiometer (350 to 2500 nm) and thermal imager (8،000 to 14،000 nm). Using a combination of visible and near-infrared spectra، crop residue cover indices were calculated and evaluated. Rresidues in NT1 and NT2 lowered the soil surface and wheat canopy temperature by 2. 5-5. 7 and 3-7°C respectively over the other treatments (MD، CH and MT). A liner negative relation between canopy temperature and wheat grain yield was found. Tillage systems were classified according to strong correlation between crop residue cover and cellulose absorption index (CAI). Conventional tillage were classified by crop residue less than 6% and CAI values below zero. Crop residue cover between 10-20% and CAI 2-4% indicated reduced tillage، and crop residue cover between 30-42% and CAI 4-5. 7% found for minimum tillage. Finally No-tillage were classified by crop residue with more than 60% and CAI values between 5. 8-8. Ground based hyper spectral signatures which were collected for identifying electromagnetic reflectance of crop residue can be used in calibration and validation of remote sensing imagery and its data products of airborne/space borne missions.