Nitrate Accumulation in Radish as Affected by Nitrapyrin1
- Harry A. Mills,
- Allen V. Barker and
- Donald N. Maynard2
Ingestion of NO3-N in vegetables represents a major source of dietary intake of NO3-N and is potentially hazardous to human health. Radish (Raphanus sativus L.), when cultured in a NO3-rich medium accumulates substantial quantities of NO3-N. The main objective of this study was to evaluate the influence of a nitrification suppressor, 2-chloro-6-(trichloromethyl)pyridine (nitrapyrin), on NO3-N accumulation in radish plants. In one study, ‘Cherry Belle’ radish was grown in pot culture under greenhouse conditions and was fertilized with KNO3 or (NH4)2SO4 to provide 0, 200, 400, 600, or 800 mg N/pot of soil (1 kg) in a factorial arrangement with pH 6.5 and pH 7.5 and with no nitrapyrin and 50 mg nitrapyrin/pot. In a second study, the same cultivar was grown with 400 mg N/pot, an amount shown to be optimum for growth in the first study, and with nitrapyrin applications of 0, 5, 10, or 50 mg/pot.
Nitrate accumulation in the plants was less with (NH4)2SO4, fertilization than with KNO3 fertilization, and all nitrapyrin applications essentially eliminated the accumulation in both roots and shoots. Total N concentrations of shoots were significantly greater with NH4-N than with NO3-N nutrition although total N in roots was unaffected by N treatment. Shoot growth was greatest with NH4-N nutrition, but root growth was restricted by NH4-N nutrition relative to NO3-N nutrition. Nitrapyrin as such had little effect on plant growth but appeared to increase the potential for NH4toxicity. Nitrapyrin caused significantly lower concentrations of NO3-N in the soil with (NH4)2SO4 fertilization but increased soil NO3-N levels with KNO3 treatments. Liming the soil had no effect on any of the factors considered in this study.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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