Effects of Chloride and Nitrogen Form on Growth of Asparagus Infected by Fusarium spp.. Wade H. Elmer, Assistant Plant Pathologist, Department of Plant Pathology and Ecology, Connecticut Agricultural Experiment Station, Box 1106, New Haven 06504. . Plant Dis. 73:736-740. Accepted for publication 10 April 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0736.

Amendments of potassium chloride or sodium chloride and the nitrogen forms Ca(NO₃)₂, KNO₃, NH₄NO₃, NH₄Cl, NH₄H₂PO₄, (NH₄)₂SO₄, or urea were examined in factorial combinations on asparagus (cv. Mary Washington) seedlings cultured in test tubes containing agar media. Greenhouse soil treatments combined each chloride salt with the following N forms: Ca(NO₃)₂, KNO₃, NH₄NO₃, or (NH₄)₂SO₄. Seedlings and 12-wk-old transplants grown with each N form, but without Cl, served as controls. Weights of seedlings were greater with NO₃-N than with NH₄-N, but growth was greatest when KCl was combined with NO₃-N. Seedlings inoculated with Fusarium oxysporum or F. moniliforme were largest when grown in combinations of Ca(NO₃)₂ and KCl or NaCl. The weights and root lengths of transplants after 10 wk increased when NaCl was added to both infested and noninfested soils, but variation was high. Similarly, disease and root colonization were reduced when NaCl was applied. Potassium nitrate produced the largest plants in noninfested soil but was more conducive to disease and fungal root colonization than the other N forms. Conversely, Ca(NO₃)₂ suppressed disease, but plants were not as large as those grown with KNO₃. Suppression of Fusarium crown and root rot of asparagus with Cl may depend on the presence of NO₃-N with adequate potassium and calcium.