GROUND-BASED X-BAND (3-CM WAVE) RADAR BACKSCATTERING OF AGRICULTURAL CROPS .1. SUGAR-BEET AND POTATO - BACKSCATTERING AND CROP GROWTH

Six years of ground-based radar observations were used to study backscattering influencing factors of agricultural crops. The X-band, 3 cm wavelength, radar backscattering of the sugar beet and the potato was studied at vertical and horizontal like-polarization and at several angles of incidence. For both crops the backscattering increased with crop growth until a saturation level was reached at about 80% soil cover. The average radar backscattering of a closed sugar beet canopy varied between - 2 db and 0 dB at all angles of incidence. The average backscattering of potato ranged from - 2 dB to 0 dB at 20-degrees incidence angle, to - 7 dB to - 5 dB at 70-degrees incidence angle. The geometry of the crop-soil system was an important backscattering influencing factor. In the potato, the orientation of the ridges with respect to the incident radar beam dominated the backscattering in the early growing season. The architecture of individual beet plants and their distribution in space affected the radar backscatter of the sugar beet. For both the beet and potato, changes in the canopy architecture due to strong winds affected the radar backscattering by 1-2 dB.