Effects of Weed Control and Row Spacing in Conventional Tillage, Reduced Tillage, and Nontillage on Soybean Seed Quality. J. E. Bowman, Former Graduate Research Assistant, University of Illinois at Urbana-Champaign, Urbana 61801. G. L. Hartman, Graduate Research Assistant, R. D. McClary, Former Assistant Plant Pathologist, and J. B. Sinclair, Professor, Department of Plant Pathology, J. W. Hummel, USDA, ARS, Associate Professor, Department of Agricultural Engineering, and L. M. Wax, Professor, USDA, ARS, Department of Agronomy, University of Illinois at Urbana-Champaign, Urbana 61801. Plant Dis. 70:673-676. Accepted for publication 3 January 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-673.

In a 3-yr study on an Illinois silt loam soil, soybean (Glycine max) seed quality was not affected by tillage practices. Under conventional, reduced, and nontillage practices, seed weight, seed germination, seedling vigor, and recovery of seedborne pathogens remained the same. In individual years, seeds from plants under nontillage had significantly (P = 0.05) lower weight and recovery of Alternaria spp. and seedborne bacteria than seeds from plants under conventional tillage, except there was a higher recovery of Alternaria spp. from seeds on 25-cm than on 75-cm centers. The highest yields and most effective weed control were found consistently in the conventional tillage plots. Weed control method affected seed quality more than either tillage or row spacing. Bentazon + sethoxydim herbicide application resulted in significantly heavier seeds but less weed control than alachlor + metribuzin. Seeds from nonweeded control plots had a significantly higher incidence of Phomopsis spp. than seeds from all herbicide-treated plots under conventional and reduced tillage but not from plots under nontillage.