Sensitivity of ASAR AP data to wheat crop parameters

This paper illustrates some results obtained in the frame of an experimental campaign carried out on several wheat fields of the Matera (Italy) site, from February 2003 to June 2004. During this period, ENVISAT ASAR data, at alternating polarization mode and at different incidence angles, were acquired on the area roughly every week. Ground data such as soil moisture content, wheat biomass, LAI etc., were also collected during the wheat growing seasons. The paper focuses on the relationship between HH/VV ASAR backscatter at high incidence angle and wheat fresh biomass as well as LAI. Observations show a strong correlation between HH/VV ASAR backscatter at about 40° and LAI from tillering to heading stage. In addition, the HH/VV-LAI relationship has been found quite robust with respect to inter-field and inter-year variability. Conversely, the HH/VV-fresh wheat biomass relationship has been found not reliable over wheat fields with significant presence of weeds. No significant differences in the HH/VV-LAI relationship between wheat and oat crops has been found. These observations indicate that, at least over the same agricultural area, it should be possible to design, implement and assess a retrieval algorithm to estimate LAI of cereal fields from ASAR AP data at high incidence angles.