A New Fiber Optic Technique for Measuring Root Growth of Soybeans Under Field Conditions1

Abstract

AbstractAn experimental procedure, described in this paper, involved the use of a highly refined fiber optic duodenoscope for observing and photographing root development patterns within a soil profile. The root was monitored by inserting the unit into a transparent Plexiglas tube imbedded within the root zone. This technique permitted the observation and quantitative characterization of the root system throughout the entire growing season, which, until this time, has been excessively expensive, laborious, time consuming, and nonreproducible. Root lengths for soybeans [Glycine max (L.) Merr. ‘Lee‐68’] at the R‐7 stage of maturity were calculated and compared by the duodenoscope and the Newman‐Core methods at four depth‐intervals. The depth intervals were reported as 0–18, 18–36, 36–54, and 54–72 cm in a Peridge silt loam (Typic Paleudalf; fine silty, mixed, mesic). Total root lengths estimated by the Newman‐Core method for the 0 to 72 cm depth‐intervals was 56.36 m, while the estimate by the scope was 52.84 m. Although both methods gave similar results, the scope tended to estimate a greater root length than did the soil cores at all depths except the 0 to 18 cm. Both methods showed that the majority of the root system was in the 0 to 18 cm depth; 68% for the soil cores and 47% for the scope. Root density (cm/cm3) decreased with soil depth from 10.58 to 1.52 by the soil core method and from 6.77 to 2.83 for the scope measurement. The coefficient of variation was 52.64 and 14.10 percent for the core and scope measurements, respectively. The study indicated that the duodenoscope method can be used as a nondestructive technique for quantitatively measuring soybean root systems throughout the growing season.