Association of Potato Early Blight, Nitrogen Fertilizer Rate, and Potato Yield. D. R. MacKenzie, Associate Professor, Department of Plant Pathology, The Pennsylvania State University, University Park 16802. Plant Dis. 65:575-577. Copyright 1981 American Phytopathological Society. DOI: 10.1094/PD-65-575.

The relationship between rate of nitrogen fertilizer application and potato yield was studied in the presence and absence of potato early blight caused by Alternaria solani. An analysis of the quadratic equation representing the response of yield to nitrogen fertilizer application indicated an optimum rate of 133 kg N/ha in the absence of potato early blight and 160 kg N/ha in its presence. Increased rates of nitrogen fertilizer application reduced the apparent infection rate and the final amount of early blight disease. Increased early blight severity was associated with decreased crop yields. Economic evaluation of the association of early blight severity, tuber yield, and nitrogen fertilizer rate suggests that, in view of current market prices and the potential for potato early blight epidemics, present recommendations for nitrogen fertilizer rates should be reevaluated.

Keyword(s): crop loss, Solanum tuberosum.