Plant Genotype Effects on Nitrogen Fixation in Grasses
Potentials for nitrogen fixation of economic importance have been shown now for a number of tropical forage grasses, sorghum, maize, rice, and perhaps even wheat. The exploitation of this potential, however, will be dependent on the identification of the limiting factors and agronomically feasible practices to eliminate them. Environmental effects are pronounced but rather difficult to manipulate. Whenever possible, preference should be given to plant-breeding practices.
Differences between cultivars and even ecotypes of Paspalum notatum in relation to the occurrence of Azotobacter paspali were shown several years ago. Differences in nitrogenase activity were then confirmed in this species, in Pennisetum purpureum, and in Digitaria decumbens. Among S1 lines of maize, several could be selected with nitrogenase activity many times higher than that of the original cultivar.
Considerable nitrogenase activity has now been shown in wheat. Estimates from 24-h intact soil core assays indicate up to 400 g N/h/day being fixed at flowering stage. Extracted root assays correlated well with the intact system (correlation coefficient r = 0.87), but gave values less than one-third of those obtained with intact soil-plant systems. Differences between cultivars were at the limit of significance.
KeywordsNitrogen Fixation Flowering Stage Intact Core Pennisetum Purpureum Original Cultivar
Unable to display preview. Download preview PDF.
- Balandreau, J. and Dommergues, Y. (1972). Assaying nitrogenase (C2 H2) activity in the field. Bull. Ecol. Res. Comm. (Stockh.) 17: 247–254.Google Scholar
- Balandreau, J. and Villemin, G. (1973). Fixation biologique de l’azote moleculaire en savanne de Lampto (Basse Côté d’Ivoire). Résultat préliminaires. Rev. Ecol. Biol. Sol. 10: 25–33.Google Scholar
- Döbereiner, J. (1970). Further research on Azotobacter paspali and its variety specific occurrence in the rhizosphere of Paspalum notatum Flugge. Centralbl. Bakt. Parasitenkunde II. 124: 224–230.Google Scholar
- Döbereiner, J. and Day, J. M. (1975). Dinitrogen fixation in the rhizosphere of tropical grasses. In IBP Synthesis Meeting: Nitrogen in the Biosphere (Stewart, W. D. P., ed.), Vol. 1, Chap. 3, pp. 39–52. Cambridge Univ. Press, Oxford.Google Scholar
- Döbereiner, J., Day, J. M., and Dart, P. J. (1972). Nitrogenase activity and oxygen sensitivity of the Paspalum—notatum—Azotabacter paspali association. J. Gen. Microbiol. 71: 103–116.Google Scholar
- Döbereiner, J., Day, J. M., and von Billow, J. F. W. (1975). Associations of nitrogen fixing bacteria with roots of forage grass and grain species. II. Int. Winter Wheat Conf Proc. pp. 221–237. Zagreb, Yugoslavia.Google Scholar
- Hardy, R. W. F., Flirter, P. and Hageman, R. H. (1975). Nitrogen Input. In Crop Productivity—Research Imperatives, International Conference, Tennessee, p. 160. Michigan State University and Kettering Foundation, East Lansing.Google Scholar
- Lee, Kuk-ki, Bonifacio, V., and Watanabe, I. (1975). Non-symbiotic nitrogen fixation in paddy soils. IRRI Saturday Seminar.Google Scholar
- Nery, M., Peres, J. R. R., and Döbereiner, J. (1975). Unpublished data.Google Scholar
- Peres, J. R. R. and da Silva, A. R. (1975). (Unpublished data from our laboratory and Centro Nacional de Pesquisa de Cerrado, Brasilia.) Google Scholar
- Rinaudo, G., Hames-Farad, I., Mouraret, M., and Dommergues, Y. (1975). N2-fixation in the rice rhizosphere: Methods of measurement; practices suggested to enhance the process. Biological Nitrogen Fixation in Farming Systems of the Humid Tropics, Conference Ibadan, Nigeria.Google Scholar
- Schank, S. and Day, J. M. (1975). (Unpublished data from our laboratory.) Google Scholar
- Tjepkema, J. D. and van Berkum, P. (1976). (Unpublished data from our laboratory.) Google Scholar
- Yoshida, T. and Ancajas, R. R. (1971). Nitrogen fixation by bacteria in the root zone of rice. Proc. Soil Sci. Amer. 35: 156–157.Google Scholar