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Effect of Chemical Soil Treatment on Plant Growth, Nitrogen Fixation, and Fungal Colonization of Rhizobium Nodules of Soybeans. K. D. Widin, Former graduate student and presently assistant professor of biology, Curry College, Milton, MA 02186; B. W. Kennedy, professor, Department of Plant Pathology, University of Minnesota, St. Paul 55108. Phytopathology 73:429-434. Accepted for publication 30 August 1982. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-429.

Hodgson soybeans, inoculated with Rhizobium japonicum, were grown in Vapam-fumigated and nonfumigated field soil for two growing seasons. Plants in nonfumigated soil showed significantly lower acetylene reduction and plant dry weight than did plants in fumigated soil during the period of pod formation in 1978. Nodule fresh weight was significantly inhibited more often than nodule number on plants grown in nonfumigated soil. Significantly more nodules and roots were colonized by fungi in nonfumigated than in fumigated soil at all but one sampling in 1979. In a one-season fungicide trial, application of captan as a soil drench did not result in significantly more plant growth and nitrogen fixation than did propamocarb drench or water alone. Gliocladium, Myrothecium, Corynespora, Trichoderma, Fusarium, and Phoma were the fungal genera most frequently isolated from soybean nodules and roots in these studies.

Additional keywords: root rot, soil fumigation, soil fungi, soil fungicides.