A radarsat-2 quad-polarized time series for monitoring crop and soil conditions in Barrax, Spain

Authors: Moran, Mary; ALONSO, L. - University Of Valencia; MORENO, J. - University Of Valencia; CENDRERO MATEO, M.P. - University Of Valencia; DE LA CRUZ, F. - University Of Valencia; MONTORO, A. - University Of Valencia

Submitted to: IEEE Transactions on Geoscience and Remote Sensing
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2011
Publication Date: 4/1/2012
Citation: Moran, M.S., Alonso, L., Moreno, J., Cendrero Mateo, M., De La Cruz, F., Montoro, A. 2012. A radarsat-2 quad-polarized time series for monitoring crop and soil conditions in Barrax, Spain. IEEE Transactions on Geoscience and Remote Sensing. 50(4): 1057-1070. https://doi.org/10.1109/TGRS.2011.2166080.
DOI: https://doi.org/10.1109/TGRS.2011.2166080

Interpretive Summary: New satellite sensors to measure radar backscatter over broad agricultural regions have been recently launched and more are planned for launch in the next decade. There is great interest in using radar images for monitoring crop and soil condition, including monitoring crop biomass, leaf area, crop residue, plant water content, crop growth stage, soil tillage and soil water content. In this study, we analyzed a time-series of 57 radar images for large fields of wheat, barley, oat, corn, onion and alfalfa in an agricultural area near Madrid Spain. We found that radar images provided information that could be used to map the distribution of crops over large areas. Further, images also provided valuable information about crop growth stage and soil moisture condition that could be used for crop management and yield prediction. The results from this study provided recommendations for planning future satellite systems to optimize the collection of meaningful information about crop and soil conditions.

Technical Abstract: An analysis of the sensitivity of synthetic aperture radar (SAR) backscatter (so) to crop and soil conditions was conducted using 57 RADARSAT-2 C-band quad-polarized SAR images acquired from April to September 2009 for large fields of wheat, barley, oat, corn, onion, and alfalfa in Barrax, Spain. Preliminary results showed that the cross-polarized so HV was particularly useful for monitoring both crop and soil conditions and was the least sensitive to differences in beam incidence angle. The greatest separability of barley, corn, and onion occurred in spring after the barley had been harvested or in the narrow time window associated with grain crop heading when corn and onion were still immature. The time series of so offered reliable information about crop growth stage, such as jointing and heading in grain crops and leaf growth and reproduction in corn and onion. There was a positive correlation between so and the Normalized Difference Vegetation Index for onion and corn but not for all crops, and the impact of view direction and incidence angle on the time series was minimal compared to the signal response to crop and soil conditions. Related to planning for future C-band SAR missions, we found that quad-polarization with image acquisition frequency from 3–6 days was best suited for distinguishing crop types and for monitoring crop phenology, single- or dual-polarization with an acquisition frequency of 3–6 days was sufficient for mapping crop green biomass, and single- or dual-polarization with daily image acquisition was necessary to capture rapid changes in soil moisture condition.