HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Pena-Cabriales, J. J. Articles by Alexander, M. Search for Related Content PubMed Articles by Pena-Cabriales, J. J. Articles by Alexander, M. Agricola Articles by Pena-Cabriales, J. J. Articles by Alexander, M.

Growth of Rhizobium in Unamended Soil¹

ABSTRACT

A study was conducted to determine the conditions in unamended soil that favored growth of Rhizobium. Moistening a dry soil resulted in growth of R. japonicum and a strain of Rhizobium nodulating cowpeas but not of R. meliloti. The extent of decline resulting from desiccation was usually greater than the increase following wetting. The extent of growth varied among soils. A freezing-thawing cycle did not promote growth of R. phaseoli and the cowpea Rhizobium. The latter bacterium was more tolerant to a freezing-thawing cycle than the former. Rhizobium japonicum and R. phaseoli grew readily in the presence of germinating seeds and developing root systems of soybeans, kidney beans, red clover, cowpeas, oats, wheat, and corn; the population size varied among the plant species, and legumes were no more stimulatory than nonlegumes. The numbers of R. phaseoli in the rhizosphere of several plants declined in 1 week, the abundance of R. japonicum fell after 6 weeks in the soybean rhizosphere, but the population size of the cowpea Rhizobium was high for at least 20 weeks. Counts of R. japonicum in soil increased after the soil was amended with soybean nodules. It is suggested that appreciable rhizobium growth in unamended soil occurs only in the presence of germinating seeds, growing roots, and decomposing nodules.

¹ Contribution from the Dep. of Agron., Cornell Univ., Ithaca, NY 14853. This study was supported by Consejo Nacional de Ciencia y Tecnologia, Mexico, Escuela Nacional de Ciencias Biologicas, IPN, Mexico, and U.S. Agency for International Development contract no. AID/DSAN-G-0090. The views and interpretations in this publication are those of the Authors and should not be attributed to the Agency for International Development or to any individual acting in its behalf.

² Graduate Research Assistant and Professor of Soil Science, respectively. Senior Author is currently at Centro de Investigacion y de Estudios Avanzados del Instituto Politecnico National—Unidad Irapuato, Apdo. Postal 629, Irapuato, GTO. 36500, Mexico.

Received for publication June 11, 1982. Accepted for publication August 20, 1982.