Effect of Soil-applied Zinc and Manganese on the Development of Rhizoctonia Aerial Blight of Soybean

Abstract

This study aimed to investigate the effect of soil-applied zinc (Zn) and manganese (Mn) rates on the development of aerial blight, caused by Rhizoctonia solani Kuhn, in soybean. Plants (cv. ‘Conquista’) were grown in a typical Acrustox red-yellow latosol amended with Zn rates (applied as ZnSO4·7H2O; 24% Zn) of 0, 1, 2, 4, 8 and 16 mg/dm3 of soil and Mn rates (applied as MnSO4·H2O; 36% Mn) of 0, 1.5, 3 and 6 mg/dm3 of soil and inoculated with R. solani. The relationship between Zn and Mn concentrations on leaf tissues and the rates of these micronutrients was linear. The incubation period was not affected by Zn and Mn rates. The relationship between application rates and the area under aerial blight progress curve was best described with a positive linear regression model for Zn and with a positive quadratic regression model for Mn. Results from this study showed that high foliar concentrations of Zn and Mn do not increase soybean resistance to aerial blight.