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

A simple two-term model of the radar backscattering coefficient of crops, d esigned Sor the retrieval of the amount of water in the canopy, is describe d and analyzed. The principle of the method is to calibrate the simple mode l 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 direc t 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-ter m model is tested against C-band radar data acquired over a soy bean crop d uring the whole vegetation cycle. The simulations correlate well with the m easurements 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 c ould be derived from the radar data. Ancillary information about soil moist ure are required, but it is found that rough estimates on a 4-5 day basis a re sufficient. (C) Elsevier Science Inc., 1999.