Effects of Chloride and Nitrogen Form on Growth of Asparagus Infected by Fusarium spp.

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Abstract
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 conductive 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.
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