Measuring Fibrous Roots with a Leaf Area Meter

Abstract

Absorption of water and salts by forage plants is dependent upon root surface area available for absorption. Estimates of root surface area can be obtained through dry weight measurement or through use of total length and average diameter estimates to calculate total surface area (Carlson, 1964; Schuurman and Goedewaagen, 1965). Root dry weight is relatively simple to obtain, but tells little about vertical penetration and lateral spread of the root system in the soil profile. Several workers have developed methods for estimating root system penetration and spread, through total root length estimates. Newman’s (1966) method involves visual counting of root intersections with randomly placed straight lines drawn on a flat surface. Rowse and Phillips (1974) modified Newman’s method by using a photoelectric counting device to record root /line intersections. Intersection counts were then converted to total length estimates by mathematical formulae. Root surface area is a good indicator of absorption ability but is difficult to determine for large sample sizes (Schuurman and Goedewaagen, 1965; Troughton, 1957). Recently, commercial leaf area meters have proven useful in making rapid direct