ORCHARDS LAI ESTIMATION THROUGH THE RADIATION EXTINCTION COEFFICIENT

Light interception is an indicator of crop vigor and phenological phase. Although algorithms found in literature are useful for calibration of direct measurement tools, they are difficult to replicate since optical corrections are needed to account for different canopy shapes. During 2016-17 growing seasons non destructive, cheap and easy to use methods to assess plant- light interaction characteristics were developed and tested in six orchards in Emilia-Romagna (Italy). The Photosynthetically Active Radiation (PAR) was detected below and above crown by an AccuPAR LP80 ceptometer, Canopy Cover (CC) was derived through hemispherical photos from a smartphone equipped with a fisheye lens, leaves for direct LAI were collected from sample plants, and measured in laboratory. The below PAR was adjusted according two geometrical corrections. The ratio above-to-below PAR was inverted to obtain the fraction of absorbed PAR (FAPAR), and to estimate the indirect LAI. Correlations between direct and indirect LAI according to plant geometry, and regardless the species, is presented. Trend lines equations were used to calculate the extinction coefficient (K), allowing LAI estimation in other orchards with similar geometrical characteristics. These studies were part of the activities supported by the MOSES European project (http://moses-project.eu/moses_website/).