Root Observations Using A Video Recording System In Mini‐Rhizotrons1

Abstract

AbstractTo understand the development of a crop, information is needed concerning the dynamics of root growth and water uptake. An extendible, 13 mm diam borescope, a low light, monochrome video camera, and a video tape recorder were combined into a system for in situ root observation through 51 mm inside diam clear acrylic tubes installed at an angle 30° from vertical. The viewing area was illuminated by two fiber optic light guides and a variable intensity light source. The observation tubes could also be used as access for a neutron probe to measure water uptake and root growth at the same point. Sector intersections rather than line intersections were counted and used to convert observations from the mini‐rhizotrons to root length densities. A comparison of root length densities determined through mini‐rhizotrons, installed in four orientations with respect to plant rows, with those determined by soil sampling indicates there was a linear relationship between the two techniques. When only depths greater than 20 cm were used the correlation was higher than when all depths were included. Results indicated that no installation orientation was clearly the best when only the depths greater than 20 cm were included. Because of the variability of the results from individual mini‐rhizotrons the results from several tubes had to be averaged before there was a satisfactory correlation with the bulk soil root length density.