Contributors; Preface; Part I. Nitrogen Fixation by Free-Living Bacteria: 1. Physiology and ecology of free-living, nitrogen-fixing bacteria E. G. Mulder; 2. Anaerobic nitrogen-fixing bacteria of different soil types E. N. Mishustin and V. T. Yemtsev; 3. Nitrogen fixation in the rhizosphere of tropical grasses Johanna Dobereiner and J. M. Day; 4. Nitrogen fixation in the rhizosphere of rice plants J. Balandreau, G. Rinaudi, Ibitissam Fares-Hamad and Y. Dommergues; 5. The Broadbalk experiment. An investigation of nitrogen gains from non-symbiotic nitrogen fixation J. Day, D. Harris, P. J. Dart and P. van Berkum; 6. Nitrogen fixation in the phyllosphere Jacoba Ruinen; 7. Associative growth of nitrogen-fixing bacteria with other micro-organisms V. Jensen and Ester Holm; 8. Nitrogen fixation associated with vascular aquatic macrophytes W. S. Silver and A. Jump; Part II. Nitrogen Fixation by Free-Living, Blue-Green Algae: 9. Nitrogen assimilation and metabolism in blue-green algae W. D. P. Stewart, A. Haystead and M. W. N. Dharmawardene; 10. The physiology of nitrogen fixation by a Gloeocapsa sp. J. R. Gallon, W. G. W. Kurz and T. A. LaRue; 11. Nitrogen fixation by blue-green algae in polar and subpolar regions Vera A. Alexander; 12. Nitrogen fixation by blue-green algae in temperate soils U. Granhall; 13. A comparison of nitrogen fixation by algae of temperate and tropical soils Elisabeth Henriksson, L. E. Henriksson and E. J. DaSilva; 14. The role of blue-green algae in tropical rice cultivation G. S. Venkataraman; 15. Research on blue-green algae in Egypt, 1958-1972 A. S. El-Nawawy and Y. A. Hamdi; 16. Nitrogen-fixing algae in Morocco J. Renaut, A. Sasson, H. W. Pearson and W. D. P. Stewart; Part III. The Acetylene-Reduction Technique: 17. The acetylene-reduction technique R. H. Burris; 18. Recent studies using the acetylene-reduction technique as an assay for field nitrogen fixation levels E. A. Paul; 19. Seasonal and diurnal variations in N2(C2H2)-fixing activity in field soyabeans C. Sloger, D. Bezdiecek, R. Milberg and N. Boonkerd; 20. Acetylene-reduction assay at ambient PO2 studies and forest soils: laboratory and field core studies R. Knowles and P. O'Toole; 21. The biochemistry of nitrogen fixation - an introduction F. J. Bergersen; 22. Some aspects of leghaemoglobin biosynthesis C. A. Godfrey, D. R. Coventry and M. J. Dilworth; 23. Preparation and properties of nitrogenase proteins R. H. Burris; 24. Morphology, reactions and characteristics of nitrogenase proteins R. W. F. Hardy, R. C. Burns, J. T. Stasny and G.W. Parshall; 25. Kinetics and mechanism of nitrogenase action R. R. Eady, B. E. Smith, R. N. F. Thorneley, M. G. Yates and J. R. Postgar; 26. Reductants for nitrogenase and relationships to cellular electron transport H. J. Evans and D. A. Phillips; 27. Relationships between nitrogenase systems and ATP-yielding processes R. O. D. Dixon; 28. Azotobacter nitrogenase: ATP kinetics and inhibition by high ionic strength R. C. Burns and R. W. F. Hardy; 29. Azotobacter nitrogenase: mechanism and kinetics if allene reduction R. C. Burns, R. W. F. Hardy and W. D. Phillips; Index.