Lincoln Biochemist’s Research Into Agricultural Nitrogen Fixation

Press, Volume XCI, Issue 27639, 21 April 1955, Page 16

Lincoln Biochemist’s Research Into Agricultural Nitrogen Fixation

A biochemist who has just returned to Christchurch after research work at the University of Wisconsin for more than two years will go back to his position at the Crop Research Division of the Department, of Scientific and Industrial Research at Lincoln with new knowledge of biological nitrogen fixation, important to many aspects of agriculture. He is Dr. Russell M. Allison, who gained a doctorate in philosophy at the University of Wisconsin while studying under a Fulbright travelling gram and a Rockefeller research grant. Explaining the nature of his work, Dr. Allison said yesterday that it was on the primary reactions Involved in nitrogen most important of the agricultural phenomena associated with crops. By its means, gaseous nitrogen of the air was fixed into compounds which could be assimilated by plants. Several kinds of organism could do that, mostly bacteria. Some of them were closely associated with plants in the form of root nodules, as on the roots of peas. Nitrogen fixation was brought. about by association with an organism called rhizobifim, which was always associated with leguminous , plants, such as peas, beans and lupins, and clover. That was the most important of the nitro-gen-fixlng systems. Action of Free Bacteria The next most important system. Dr. Allison said, was the fixation of nitrogen brought about by free living bacteria—those not associated with plants, but living free in the soil. Among the best known was the azotobacter group which fixed molecular nitrogen and required a lot of oxygen. But other organisms such as Clostridia, which were anerobes, required the absence of oxygen to fix. It was in soils that there was a contribution of both the latter types towards the amount of nitrogen in building up fertility. His problem at Wisconsin concerned the azotobacter group of free-living organisms, he said. The idea was to feed the organism molecular nitrogen which contained the stable isotope of nitrogen, which was heavier than normal, and called Nl5. After it had been allowed to fix the isotopically enriched gas for a short time, the nitrogencontaining compounds of the organism and the amount of Nl5 present in each of the given compounds enabled an idea to be gained of which compound was the first to be labelled with Nl5. That gave clues as to the primary product of fixation in the organism. "From the point of view of compara-

five biochemistry. It is unlikely that any other mechanism is as important as the one we found—in this case the primary product in ammonia,” Dr. Allison said. Describing the method of approach, Dr. Allison said, that with the stable isotopes, it was necessary to use a mass spectrometer which separated the two masses of Nl4 and Nl5, and the relative abundance of the two was measured electronically on a complicated piece of machinery, originally developed in England by Dr. Aston in the 1920'5. There was one mass spectrometer in New Zealand, at the Dominion Physical Laboratory in Wellington, and this was available for work with stable isotopes. Applied research depended on fundamentals for its raw materials, so in the long run a basic understanding of nitrogen fixation would lead to an increased use of what widespread biological phenomenon in agriculture, Dr. Allison said, discussing the terms of application of such research. It could be applied in all phases of agriculture. In pasture management, for instance, it was known that the ideal for New Zealand was ryegrass and clover combined. That depended largely on the root nodules on the clover, and their ability to fix nitrogen. It was also true and well known that, in standard cropping procedure, wheat was grown, then peas. The peas, with their root nodules and ability to fix nitrogen, raised the nitrogen status of the soil to what it was before the wheat had taken it out. Dr. Allison said the Crop Research Division was most interested in improving methods of crop agriculture by using the ability of the organisms to fix nitrogen. It was also interested in the ability of the free living organisms, azotobacter and Clostridia, to raise the nitrogen status of the soil He hoped to carry on with some aspects of the work, because the basic tool was available in Wellington. Dr. Allison visited various universities and institutions in the United States that were doing fundamental work on plant nutrition and the study of plant enzimes. A small group at Berkeley University, California, was doing nitrogen fixation research under Dr. Delwiche, he said. Many of the universities were right in the foretront in their various fields, helped b Y the first-class facilities in laboratories.

I will go back to Lincoln to put into operation the techniques of research I have learned and the knowledge gained from discussing problems,' Dr. Allison said.