Plant Growth Regulation

, Volume 3, Issue 1, pp 71–78 | Cite as

Effects of plant growth regulators in soil on clover growth and nitrogen fixation

  • D. J. Fisher
  • L. Hayes
Article
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Abstract

Effects of the growth regulators Barleyquat B, New ‘5c’ Cyocel, Cerone, Terpal and paclobutrazol on Rhizobium trifolii in vitro, on growth and root nodulation of clover grown in pots and on symbiotic nitrogen fixation were measured.

Paclobutrazol in soil markedly reduced the weight of clover plants but had no effect on nodulation in relation to plant size. Paclobutrazol decreased the amount of nitrogen fixed per plant (measured by acetylene reduction) when present in soil at a concentration which would result from a single direct application at 0.25 kg a.i. ha−1 remaining unchanged and evenly distributed in the top 5 cm of soil. A concentration in soil equal to that from an application at 0.125 kg a.i. ha−1 had no significant effect on the rate of nitrogen fixation per plant and the rate relative to plants weight increased. It was evident that the inhibitory effect on plant growth was greater than on symbiotic nitrogen fixation. The other PGR's had virtually no effect on clover.

None of the compounds seems likely to affect nitrogen fixation by a subsequent clover crop in the field if previously applied to a cereal crop once at typical rates of application.

Key words

Clover Rhizobium nitrogen-fixation soil-residues growth regulators 

Zusammenfassung

Die Einflüsse der Wachstumsregulatoren Barleyquat B, New ‘5c’, Cyocel, Cerone, Terpal und Paclobutrazol auf das Wachstum von Rhizobium trifolii in vitro, auf das Wachstum und Knöllchenbildung des Klees und auf die symbiotische N2-Bindung wurden bestimmt.

Paclobutrazol im Boden führte zu einer bedeutenden Gewichtsverminderung der Kleepflanzen, blieb aber ohne Einfluß auf die Knöllchenbildung in bezug auf die Pflanzengröße. Paclobutrazol reduzierte die Menge Stickstoff gebunden pro Pflanze, (gemessen mittels Acetylenreduktion) wenn er im Boden in einer Konzentration enthalten war, die anwesend wäre, wenn eine einzige Applikation von 0,25 kg Wirkstoff.ha−1 unverändert und gleichmäßig in den oberen 5 cm des Bodens verteilt bleiben würde. Eine Bodenkonzentration gleich jener von einer Applikation von 0,125 kg Wirkstoff.ha−1 hatte keine signifikante Wirkung auf die N2-Bindungsleistung pro Pflanze, und das Bindungstempo in bezug auf das Pflanzengewicht nahm zu. Offensichtlich war die Hemmwirkung auf das Pflanzenwachstum größer als auf die symbiotische N2-Bindung.

Wahrscheinlich wird keine der Verbindungen die N2-Fixierung des Klees im Freiland beeinträchtigen, wenn sie einmal vorher auf eine Getreidearte in der üblichen Aufwandmenge appliziert werden.

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Copyright information

© Martinus Nijhoff/Dr W. Junk Publishers 1985

Authors and Affiliations

  • D. J. Fisher
    • 1
  • L. Hayes
    • 1
  1. 1.Long Ashton Research StationUniversity of BristolBristolU.K.

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