Juglone (5-hydroxy-1,4 napthoquinone) and soil nitrogen transformation interactions under a walnut plantation in southern Ontario, Canada |
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Authors: | N V Thevathasans A M Gordon R P Voroney |
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Institution: | (1) Agroforestry, Department of Environmental Biology, University of Guelph, Guelph, Ontario, N1G 2W1, Canada;(2) Department of Environmental Biology, University of Guelph, Guelph, Ontario, Canada;(3) Department of Land Resource Science, University of Guelph, Guelph, Ontario, Canada |
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Abstract: | Juglone (5-hydroxy-1,4-naphthoquinone), a chemical substance produced by black walnut (Juglans nigra L.), inhibits the growth
and existence of some beneficial soil microorganisms, especially Frankia spp. isolate ArI3 and Rhizobium japonicum. However,
no studies to date have reported on the effect of juglone on soil ammonification and nitrification. A field study and laboratory
incubation study to investigate this were conducted. In the field, in situ soil ammonification and nitrification were measured
within and outside of a 60-year-old black walnut plantation and a eight-year-old poplar (Populus spp. clone DN 177) plantation.
In the lab, soil (Sandy Fox Loam), collected in the absence of black walnut trees, was incubated for periods of one to six
weeks in the presence of varying concentrations of juglone. In the field, peak summer mean nitrate accumulation rates in soils
within the black walnut and poplar plantation were 163 and 95 μg 100 g-1 dry soil day-1 respectively and in soils outside the plantations, 104 (black walnut) and 78 (poplar) μg 100 g-1 dry soil day-1 respectively. No accumulation of ammonium at the end of the incubation period was noted. Therefore, no inhibition effect
of juglone on nitrification in the field was observed, and laboratory incubation results confirmed the results of the field
study. Results from these studies should address concerns about nitrification inhibition under walnut based intercropping
systems.
This revised version was published online in June 2006 with corrections to the Cover Date. |
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Keywords: | allelopathy intercropping nitrification poplar walnut juglone |
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