Effects of Soil Compaction on the Incidence of Phytophthora megasperma f. sp. glycinea in Soybean. C. K. Moots, Former Graduate Research Assistant, Department of Agronomy, University of Illinois, and USDA-ARS, Urbana 61801. C. D. Nickell, and L. E. Gray. Professor, Department of Agronomy, and Associate Professor and Plant Pathologist, Department of Plant Pathology, University of Illinois, and USDA-ARS, Urbana 61801. Plant Dis. 72:896-900. Accepted for publication 15 May 1988. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0896.

Soil compaction experiments were conducted for 2 years on a poorly drained soil with a natural infestation of Phytophthora. Prior to planting, the compaction treatment was imposed on strips selected at random in the plot area by repeatedly driving a tractor over the plots. Soil compaction treatments significantly increased soil bulk density in compacted vs. uncompacted plots in both years. Soil compaction significantly increased the incidence of Phytophthora root rot. The increased disease incidence helped differentiate susceptible from resistant cultivars. This implies that soil compaction could be useful in identification of susceptible soybean lines from breeding programs. Disease incidence and area under the disease progress curve were both found to be good measures of cultivar resistance to Phytophthora.