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Chloride, Nitrogen Form, Lime, and Planting Date Effects on Take-All Root Rot of Winter Wheat. R. G. Taylor, Graduate Research Assistant, Oregon State University, Corvallis 97331. T. L. Jackson, Professor, Department of Soil Science, R. L. Powelson, Department of Botany and Plant Pathology, and N. W. Christensen, Associate Professor, Department of Soil Science, Oregon State University, Corvallis 97331. Plant Dis. 67:1116-1120. Accepted for publication 18 April 1983. Copyright 1983 American Phytopathological Society. DOI: 10.1094/PD-67-1116.

Field experiments conducted in western Oregon showed that losses caused by take-all root rot of wheat (Gaeumannomyces graminis var. tritici) could be significantly reduced through crop management and fertilization practices. Improved crop performance resulted from seeding late and using fertilizers containing ammonium nitrogen (NH4-N), phosphorus (P), and chloride (Cl). Increased grain yield of take-all-infected plants was greatest in response to delayed seeding and Cl fertilization, whereas root infection was most effectively suppressed by NH4-N. The potential for take-all was lower when the soil pH was between 5.6 and 6.0. Lime and P applications on a strongly acid (pH 5.2), P-deficient soil reduced the incidence of whiteheads associated with take-all, whereas previous lime treatments on a moderately acid (pH 5.6), high P status soil favored attack by take-all and caused yields to decline. Although the influence of seeding date, N form, lime, and P on take-all severity have been studied extensively, the involvement of Cl in take-all suppression has only recently been demonstrated.