|Kamuru, F. - UNIVERSITY OF FLORIDA|
|Albrecht, S. - UNIVERSITY OF FLORIDA|
|Shanmugam, K. - UNIVERSITY OF FLORIDA|
Submitted to: Applied Soil Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 16, 1996
Publication Date: N/A
Interpretive Summary: The lack of nitrogen fertilizer is the main limit to crop production globally. Much of the success of the "Green Revolution" was due to increased rates of nitrogen applied to crops that were selected to take maximum advantage of more nitrogen. Much of the nitrogen available to paddy-culture (shallow-flooded) rice can be supplied by nitrogen-fixing cyanobacteria and by Azolla (cyanobacteria growing in association with a tiny green plant), both of which grow in paddy fields. This experiment showed that an ammonium-excreting mutant strain of a cyanobacterium supplied enough nitrogen to cause 60% more rice growth than its parent strain. Furthermore, this mutant strain caused about 17% more plant growth than rice fertilized with 45 pounds of nitrogen per acre. Thus, the mutant strain shows potential as a nitrogen source for rice growth in low-input, sustainable, paddy rice agriculture.
Technical Abstract: Rice plants grown in fleakers were inoculated with the parent and nitrogenase-derepressed mutant strain of the cyanobacterium Anabaena variabilis and exposed to N-15 gas. Dry matter and total N accumulated in the roots and shoots of plants inoculated with the mutant strain were significantly greater than that obtained from plants inoculated with the parent strain. Fixed N from the mutant strain was more available for uptake and assimilation by the plants, as evidenced by the significantly higher levels of N-15 accumulated in the roots and shoots of plants inoculated with the mutant strain. Uninoculated plants exposed to N-15 had a small, insignificant increase in levels of N-15 in the roots and shoots compared to the inoculated and control plants that were not exposed to the isotope. After 49 days of growth, this experiment showed that the ammonium-excreting gnitrogen to cause 60% more rice growth than its parent strain. Furthermore, this mutant strain causes about 27% more plant growth than rice fertilized with 50 kilograms of nitrogen per hectare. The mutant strain shows potential as a source of N for plant growth in sustainable, low-rice production systems.