Influence of Chloride and Nitrogen Form on Rhizoctonia Root and Crown Rot of Table Beets

The effect of NaCl combined with Ca(NO₃)₂ or (NH₄)₂SO₄ was examined on table beets (Beta vulgaris) in the presence and absence of Rhizoctonia solani (anastomosis group 2-2), the cause of Rhizoctonia root and crown rot. Transplants of cvs. Detroit Dark Red and Early Wonder grown in the greenhouse in infested soils and fertilized with Ca(NO₃)₂ (10 mmol of N) were 32% larger in dry weight than plants treated with (NH₄)₂SO₄ (10 mmol of N). In noninfested soils, a 17% increase in dry weights was observed for plants treated with Ca(NO₃)₂ compared to plants that were fed (NH₄)₂SO₄. When NaCl (0.17 mmol) was applied, the mean dry weight sincreased 40% in noninfested soil and 12% in infested soil compared to plants that received no NaCl. No significant interaction occurred between N fertilizer and NaCl in greenhouse trials. However, in field soils infested with R. solani, NaCl (560 kg/ha) combined with (NH₄)₂SO₄ (112kg of N per ha) produced 26 to 47% more root yield than when (NH₄)₂SO₄ was used alone. Inthe absence of NaCl, Ca(NO₃)₂ suppressed disease more than (NH₄)₂SO₄, but adding NaCl to Ca(NO₃)₂ did not increase yield more than Ca(NO₃)₂ alone. The Cl salts KCl, CaCl₂, and MgCl₂did not significantly differ from NaCl in their ability to increase the dry weight of beets grownin infested soils. Leaf and root analyses revealed that (NH₄)₂SO₄ applications increased N, P, S, and Mn in tissue more than Ca(NO₃)₂ applications. Applying NaCl increased tissue levels of Na, Cl, and Mn more than in plants that were not fed NaCl. All of the Cl salts had the effect of increasing concentrations of Cl and Mn in the plant. There was no evidence that the Na ion was disease suppressive. Chloride, however, may be of use in disease management of Rhizoctonia root and crown rot of table beets.