COMPARISON OF AMMONIUM-SULFATE AND CALCIUM NITRATE FERTILIZATION EFFECTS OF VERTICILLIUM WILT OF EGGPLANT

Eggplants fertilized with either (NH4)2SO4 or Ca(NO3)2 were grown over three seasons in soil with high, low, or no inoculum of Verticillium dahliae. Early in the season before the onset of symptoms, eggplants t reated 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 pseudom onads were not affected by nitrogen fertilizers. After anthesis when s ymptoms appeared, the fertilizer treatments did not affect the percent age 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 fertili zation with Ca(NO3)2. In soils with high inoculum density, there was n o difference between the nitrogen fertilizers in effect on eggplant gr owth or yield. In soils with low inoculum densities, however, plants f ertilized with (NH4)2SO4 were significantly larger, had more large lea ves 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 Vertici llium wilt of eggplant.