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Influence of Soil Bulk Density and Water Potential on Fusarium Root Rot of Beans. D. E. Miller, Soil Scientist, Agricultural Research Service, U.S. Department of Agriculture, Western Region, Irrigated Agriculture Research and Extension Center, Prosser, Washington 99350; D. W. Burke, Research Plant Pathologist, Agricultural Research Service, U.S. Department of Agriculture, Western Region, Irrigated Agriculture Research and Extension Center, Prosser, Washington 99350. Phytopathology 64:526-529. Accepted for publication 29 October 1973. DOI: 10.1094/Phyto-64-526.

The influence of soil bulk density and water potential on injury to beans by Fusarium root rot was evaluated in the laboratory. A technique was used by which soil water potential could be maintained relatively constant, without the alternate wetting and drying that accompanies periodic irrigation. Growth of tops and roots was consistently reduced by decreasing water potential from 200 to 800 mb. Yields of tops and of roots within or above a restrictive soil layer were lower in infested soil than in fumigated soil. However, the roots that penetrated the layer grew equally well and were healthy in both soils. The bulk density of a central soil layer had little effect on top yields. In fumigated soil, root growth above the most-dense layer was greater than above the less-dense layers; while in root rot soil, root growth above the layer was not affected by layer bulk density. The detrimental effects of decreased water potential, Fusarium infestation, and increased layer bulk density were additive.

Additional keywords: Phaseolus vulgaris L., soil compaction, root impedance.