Effects of 2,4-d on nitrogen fixation and carbon dioxide evolution in a soil microcosm |
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Authors: | John L Malanchuk Kate Joyce |
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Institution: | 1. Institute for Man and Environment and Department of Biological Sciences, State University of New York, 12901, Plattsburgh, NY, U.S.A.
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Abstract: | Two concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D) 1.7 kg ha?1 and 3.4 kg ha?1 were applied to oats (Avena sativa L. ‘Orbit’) grown in terrestrial microcosms in a sandy soil. Carbon dioxide evolution and non-symbiotic N2 fixation (C2H2 reduction) were measured weekly. On day 70 of the study, 2,4-D was applied a second time at the same application rates and soil CO2 evolution and N2 fixation were measured more frequently. Soil CO2 evolution over 24 h period was significantly decreased by 40 to 50% at both application rates of 2,4-D. This response lasted less than 7 days. Nitrogen fixation was unaffected by 2,4-D except for an unexplained decrease observed in the 1.7 kg ha?1 treatment 35 days after 2,4-D application. This effect was not observed on the following sampling date. The second application of 2,4-D failed to produce any significant change in soil CO2 evolution or N2 fixation. From these studies we conclude soil microbial populations either degraded or became acclimated to 2,4-D as a result of the initial application and that 2,4-D has no significant adverse effect on N2 fixation or soil CO2 evolution. |
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