The production of rice has increased considerably in recent years due to the release of improved varieties and the adoption of better fertilization practices. Nevertheless, the production and use of inorganic N fertilizer involves costly investments in terms of energy and transport, the need for complex manufacturing plants, as well as the potential for environmental pollution. The use of agricultural systems that include dinitrogen fixing organisms appears to be an economically sound cultural practice. In the particular case of rice, biological nitrogen fixation by Azolla, blue-green algae (BGA), and heterotrophic microorganisms has long been recognized, in southeast Asia, as a fertilizer for rice culture. The Azolla-Anabaena association has the unique property of being able to retain a significant amount of nitrogenase activity in the presence of combined nitrogen, making the system compatible with inorganic nitrogen fertilization. Researchers working with Azolla (N fixation) are dispersed in 2 countries of southeast Asia, Africa, Europe and Latin America, making it difficult to share ideas, concepts and research results on a more personal basis. Considering the potential positive impact of growing rice in association with Azolla, and the lack, to date, of an international gathering of scientists dedicated to Azolla research, the First International Workshop on "Practical Applications of Azolla for Rice Production" was organized by the University of Puerto Rico-Mayaguez Campus.

Proceedings of an International Workshop, Mayaguez, Puerto Rico, November 17-19, 1982

Inhalt

1. Azolla-Anabaena symbiosis: Basic Biology, Use and Prospects for the future.- First Section: Basic Studies.- 2. Formation and breakdown of Azolla polypeptides in paddy soils.- 3. Determining N2 fixation and N input in Azolla grown with and without combined nitrogen sources: keeping the acetylene reduction assay in the proper perspective.- 4. Recent advances on Azolla research.- 5. Sporocarp germination, cytology and mineral nutrition of Azolla species.- 6. Azolla pinnata var. africana. Background, ecophysiology, plots assays.- 7. A scanning electron microscopic view of sporulation in Azolla mexicana Presl.- 8. Planning Azolla research for the 1980's.- Second Section: Applied Studies.- 9. Azolla, a water saver in irrigated rice fields?.- 10. Azolla A potential biofertilizer for rice production.- 11. Comparative study of six species of Azolla in relation to their utilization as green manure for rice.- 12. Azolla bio-fertilization to increase rice production with emphasis on dual cropping.- 13. Manuring of rice crop with Azolla.- 14. Phosphorus removal by Azolla caroliniana cultured in nutrient enriched waters.- 15. Utilization of radioactive phosphorus (32P) by Azolla-Anabaena and its transfer to rice plants.- 16. A study of the availability of biologically fixed atmospheric dinitrogen by Azolla-Anabaena complesx to the flooded rice crops.- Third Section: Country Studies.- 17. Azolla for rice production in Thailand.- 18. Azolla as a biofertilizer for rice in Sri Lanka.- 19. Azolla in West Africa: First results from the WARDA Program.- Fourth Section: Abstracts.- 20. Response of rice to nitrogen fertilization in Puerto Rico.- 21. Research on the mass culture of Azolla caroliniana and A. filiculoides in Italy.- 22. Practical utility of Azolla in Samba season in Thanjavur Delta.- 23. Azolla for rice production in tropical Africa.- 24. Evaluation of the Azolla-Anabaena association effect on the dry matter production and total N of Setaria sphacelata cv. Kazungula.- 25. Phosphorus nutrition in Azolla.- Fifth Section: Round Table.- 26. Conclusions.- List of participants.- Author index.- Key words index.