Dicke, Robert J. (ed.) / Transactions of the Wisconsin Academy of Sciences, Arts and Letters
volume XLIV (1955)
Persidsky, D. J.; Wilde, S. A.
Effect of eradicants on the microbiological properties of nursery soils, pp. 65-73 ff. PDF (2.7 MB)
65EFFECT OF ERADICANTS ON THE MICROBIOLOGICAL PROPERTIES OF NURSERY SOILS' D. J. PERSIDSKY and S. A. WILDE2 Current nursery practice employs a large number of toxic compounds, or eradicants, for the control of destructive insects, parasitic fungi, and noxious weeds. The application of these chemicals is not without adverse influence upon the beneficial soil organisms, state of soil fertility, and the growth of nursery stock. This study aimed to detect the effects of commonly used eradicants upon microbiological characteristics of soils which serve as indicators of unimpaired soil productive capacity. The trials were conducted in greenhouse cultures with outwash siliceous sand possessing a reaction of about pH 5.0, exchange capacity of 1.9 m.e. per 100 g., and 0.7 per cent of organic matter. The biocides studied included chlordane, benzene hexachloride, calomel, thiosan, aluminum sulfate, formaldehyde, allyl alcohol, and Stoddard solvent. These were applied at the rates slightly exceeding those used in current nursery practice. Such treatments were justified in view of the local concentration of chemicals resulting from their uneven distribution under conditions of actual soil management. The following microbiological characteristics were investigated: the relative ' density of micropopulation, rate of cellulose and protein decomposition, nitrification capacity, rate of carbon dioxide evolution, growth of excised roots under the influence of volatile substances emitted by the soil, growth responses of Aspergillus niger, and the development of mycorrhizal short roots. Monterey pine, Pinus radiata, was used as a test plant and a carrier of symbiotic organisms. The extreme poverty of the soil, the use of enclosed containers, and fluctuating content of soil moisture, unavoidable in watering by hand, all undoubtedly contributed to the adverse effects of biocides. The number of microorganisms present in untreated and biocide-treated soils was determined on the basis of colonies develo'ped on the molecular membrane filters (Clark et al., 1951). 1 Contribution from the Soils Department, Wisconsin Agricultural Experiment Station, Madison, Wisconsin. This study was carried out with the assistance of a grant from the Research Program on the U.S.S.R. (East European Fund, Inc., New York City). Publication approved by the Director of the Wisconsin Agricultural Experiment Station. 2 Research Associate and Professor of Soils, respectively.
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