THE ESTIMATION OF GROUND COVER OF POTATO BY REFLECTANCE MEASUREMENTS

In nine field trials, the proportion of ground covered by potato canopy was estimated using near-infrared and visible reflectance measurements. The data set spanned a range of cultivars, treatments, soil types, soil moisture regimes and growing conditions that ranged from severely stressed to near-potential growth. Near-infrared reflectance of the canopy, corrected for soil reflectance (WDVI), was related to ground cover estimated by a trained expert with or without the use of a grid-frame. Different linear regressions between ground cover and WDVI for the early phase of growth and for the late phase, allowed the calculation of ground cover of potato from WDVI with an absolute accuracy of 3.5 - 6.5 %. The derived regression lines are expected to have a general applicability for potato grown on soils of temperate regions. It is concluded that reflectance measurement is an objective, fast and reliable method for estimating the proportion of ground covered by potato canopies.