A simple approach to monitor crop biomass from C-band radar data

A simple two-term model of the radar backscattering coefficient of crops, designed Sor the retrieval of the amount of water in the canopy, is described and analyzed. The principle of the method is to calibrate the simple model front the simulations of a discrete first-order radiative transfer model during crop development. The canopy structure is taken into account in the discrete model to compute the relationships between a) the vegetation direct contribution to backscattering sigma(v)(o) and the optical depth tau and b) the optical depth tau and the amount of water in the canopy. The two-term model is tested against C-band radar data acquired over a soy bean crop during the whole vegetation cycle. The simulations correlate well with the measurements and the retrieval of the amount of water it the canopy Wc (kg/m(2)) can be carried out. Accurate temporal information on the crop growth could be derived from the radar data. Ancillary information about soil moisture are required, but it is found that rough estimates on a 4-5 day basis are sufficient. (C) Elsevier Science Inc., 1999.