Nitrogen fixation of lucerne (Medicago sativa) in an acid soil: The use of rhizotrons as a model system to simulate field conditions |
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Authors: | J W M Pijnenborg T A Lie |
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Institution: | (1) Department of Microbiology, Wageningen Agricultural University, Hesselink van Suchtelenweg 4, 6703 CT Wageningen, The Netherlands |
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Abstract: | The effect of pelleting seeds of lucerne with lime was studied in an acid sandy soil. In pot experiments, the fraction of seedlings with crown nodules, i.e. nodules on the upper 10 mm of the taproot, increased from 26% to 71%. In rhizotrons, the application of CaCO3 resulted in an even stronger response.An agar-contact method was used to study pH changes in the rhizosphere during a period up to 12 days. Application of 1.0 µmol of CaCO3, in drops of 12 µL volume, resulted in an initial soil pH of 6.1 and yielded 75% crown nodulation. In the absence of CaCO3, roots induced a pH increase from 5.1 (day 0) to 5.7 (day 12). However, this did not increase nodulation (5%). Obviously, this type of alkalinization does not overcome the acid-sensitive step of the nodulation process. |
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Keywords: | acid soil agar-contact method Medicago sativa L nitrogen fixation pH micro-electrode Rhizobium meliloti rhizotron |
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