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Quantitative Evaluation of a Leaching Model System for Soil Fungistasis. J. L. Lockwood, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824; Phytopathology 65:460-464. Accepted for publication 7 November 1974. DOI: 10.1094/Phyto-65-460.

Filter paper disks, each containing 45 µg glucose, were incubated on smoothed soil in petri dishes. Loss of glucose from such disks was linear with logarithm of time from 30 to 240 minutes. Glucose loss was more rapid with natural than with autoclaved soils, with the difference detected within 8 minutes. A model system designed to mimic this microbial glucose sink through continuous aqueous leaching of a bed of glass beads was calibrated by measuring glucose loss from disks incubated on the beads. At low flow rates (2-5 ml/hr) glucose loss characteristics were similar to those for soil. As flow rates increased up to 60 ml/hour, early losses exceeded those on soil, resulting in progressively decreased glucose half-lives; however, slopes after 15 minutes steepened only slightly. Germination of conidia of Curvularia lunata, Helminthosporium sativum, and H. victoriae in the leaching system decreased as flow rates increased. High flow rates (> 20 ml/hour) were required to reduce germination to the level occurring on soil.