Effect of Sodic Water and Irrigation on Sodium Levels and the Development of Early Leaf Spot in Peanuts. D. M. Porter, Research Plant Pathologist, U.S. Department of Agriculture, Agricultural Research Service, Tidewater Agricultural Experiment Station, Suffolk, VA 23437. F. J. Adamsen, Soil Scientist, U.S. Water Conservation Lab, Phoenix, AZ 85040. Plant Dis. 77:480-483. Accepted for publication 29 December 1992. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1993. DOI: 10.1094/PD-77-0480.

Concentrations of sodium in plant tissues and soil, and the severity and incidence of early leaf spot (Cercospora arachidicola), were influenced by water quality (sodic or nonsodic water) and method of irrigation (sprinkle or trickle). Mean Na levels were always higher in tissues (leaf, stem, root, and seed) of plants receiving sprinkle-applied deep-well water containing an average Na concentration of 220 mg L^–1 and a sodium absorption ratio (SAR) of 103, than in plots receiving sprinkle-applied shallow-well water containing an average Na concentration of 4.8 mg L^–1 and an SAR of 3.1. Na levels also were usually higher in tissues of sprinkle-irrigated than of trickle-irrigated plants. Na in root tissues generally was highest in sprinkle-irrigated plants receiving sodic water. Soil Na was higher in plots receiving sodic water; irrigation method (sprinkle or trickle) did not influence soil Na. The incidence and severity (percentage of defoliation, diseased leaflets, and number of lesions per leaflet) of early leaf spot was usually greater in sprinkle-irrigated plants and in plants receiving sodic water. The mean percentages of diseased leaflets, defoliation, and number of lesions per leaflet were 25, 60, and 35% greater, respectively, in plants receiving sodic irrigation water than in plants receiving nonsodic water.