Row structure and foliage geometry as determinants of the interception of light rays in a sorghum row canopy.
Abstract. The interception of light rays by the canopy of a widely spaced sorghum row crop was assessed from a series of hemispherical photographs taken on five occasions during its vegetative growth. Analysis of the photographs shows that most of the temporal and spatial variation in the canopy's interception could be accounted for by treating the row as an array of solid parallel walls with rectangular cross sections. Within the space occupied by rows, the effect of the distribution of foliage elements on interception could be assessed by the porosity of a single row. The north-south asymmetry observed in the distribution of ray interception indicates that this sorghum canopy, grown under unirrigated, arid summer conditions, adopted a light-avoiding growth pattern.