Organic Matter and N Effects on Soil Nitrite Accumulation and Resultant Nitrite Toxicity to Tobacco Transplants1
- James L. Hamilton and
- Richie H. Lowe2
Extended rainy periods during the first few weeks after setting tobacco (Nicotiana tabacum L.) may result in a disorder of tobacco called organic matter toxicity. The decay of organic matter in a soil with moisture levels near field capacity (where O2 diffusion is slower) may deplete the soil O2 enough that nitrite accumulates. Our purpose was to study the accumulation of nitrite in soil with organic matter and N added, and the toxicity of nitrite to tobacco.
To determine the effects of nitrite, burley tobacco (‘Ky 14’) was transplanted into pots containing gravel and irrigated with half-strength Hoagland solution plus 0, 5, 10, and 15 ppm of nitrite. Tobacco root tips were killed when ntrite concentrations exceeded 5 ppm.
To determine the effects of organic matter and N fertilizer of nitrite accumulation in soil, we determine weekly for 8 weeks the nitrite concentration in pots with: a) organic matter and N fertilizer added, b) only N added, and c) neither organic matter nor N added (controls). Moisture was adjusted to 90% field capacity each day. Tobacco plants were transplanted into the pots at 2, 4, and 6 weeks after preparing the treatments. Nitrite accumulated in the soil layer containing organic matter for 2 weeks, reaching a concentration of 60 ppm. It then started to decrease but remained at toxic levels for 5 weeks. Where no organic matter was added with the N, nitrite levels were toxic only in the sample taken the first week. Tobacco plants transplanted to soil 2 weeks after organic matter was added never grew or developed a root system. The dry weight of plants transplanted 4 weeks after organic matter was added was about one-half that of the control and plants transplanted 6 weeks after treatments were applied did not differ.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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