Comparison of Ammonium Sulfate and Calcium Nitrate Fertilization Effects on Verticillium Wilt of Eggplant. WADE H. ELMER, Associate Plant Pathologist, Department of Plant Pathology and Ecology, Connecticut Agricultural Experiment Station, Box 1106, New Haven 06504. FRANCIS J. FERRANDINO, Assistant Scientist, Department of Plant Pathology and Ecology, Connecticut Agricultural Experiment Station, Box 1106, New Haven 06504. Plant Dis. 78:811-816. Accepted for publication 5 May 1994. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-0811.

Eggplants fertilized with either (NH4)2SO4 or Ca(NO3)2 were grown over three seasons in soil with high, low, or no inoculum of Venicillium dahliae. Early in the season before the onset of symptoms, eggplants treated with (NH4)2SO4 had more nonstructual carbohydrates in the roots and leaves than plants treated with Ca(NO3)2, and the rhizosphere was more acidic. Densities of total rhizobacteria and fluorescent pseudomonads were not affected by nitrogen fertilizers. After anthesis when symptoms appeared, the fertilizer treatments did not affect the percentage of diseased foliage or the amount of root and stem colonization by V. dahliae. However, fertilization with (NH4)2SO4 was associated with increased leaf and root levels of N, P, and Mn, compared with fertilization with Ca(NO3)2. In soils with high inoculum density, there was no difference between the nitrogen fertilizers in effect on eggplant growth or yield. In soils with low inoculum densities, however, plants fertilized with (NH4)2SO4 were significantly larger, had more large leaves and fewer small leaves, and had 33-44% more marketable yield than plants fertilized with Ca(NO3)2. Fertilization with (NH4)2SO4 in soil with low inoculum densities may be useful in the management of Verticillium will of eggplant.

Keyword(s): mineral nutrition, soilborne pathogens