|dc.description.abstract||A great variety of work concerning Rhizobium has been published for many decades. Long before published material in scientific journals ever existed, the agricultural importance of legumes was known. The Egyptians used legumes about 5000 B.C. and the Swiss lake dwellers in 2000 B.C. Theophrastus, 370-285 B.C. wrote in his Enquiry into plants of the “reinvigorating” effect on the soil. The Athenians celebrated the Feast of beans in honour of Apollo. The Greek Diogenes Laertius said, “Beans are the substance which contains the largest portion of that animated matter of which our souls are particles” (Fred, Galdwin and McCoy, 1932).
By the nineteenth century, the foundations of present day farming methods were established. The work of Albrecht Thaer and Schultz-Lupitz greatly influenced work concerning the Leguminosae. Albrecht Thaer advocated raising legumes between cereal crops, and Schultz-Lupitz in his paper of 1881 stated “plants as clover, lupines, and peas are able to utilise nitrogen in some form other than that required by non-leguminous plants” (Fred et al., 1932).
Isolated problems had to be solved by the sciences of botany, plant physiology, chemistry and bacteriology, before the reasons why leguminous crops were beneficial, were to be known. In 1774-77 priestly concluded that plants absorbed free nitrogen from the air. But it was the classical work of Boussingeult in 1838 that revealed peas and clover could apparently take nitrogen from the air while wheat could not. He concluded that the nitrogen source was the ammonia of the air however, he discounted his results because the plants had grown in the open air. In 1851 he grew the plants in sterilized pumice stone and in a known volume of air in a glass chamber supplied with a continuous flow of ammonia free air, and his plants grew poorly.
In 1885 Berhthelot was the first to suggest that bacteria might be involved in the nitrogen fixing process. Soon after Hellriegel and Wilfarth published a paper (1883) proving unequivocally that root nodules were responsible for the ability of leguminous plants to use atmospheric nitrogen (Fred et at., 1932).
Biejerinck first isolated and cultivated these nodule bacteria from root nodules in 1888. From this discovery a great deal of work began with the nodule bacteria being cultivated on a variety of bacterial media.
New Zealand’s agricultural economy is mainly dependent on a form of farming which characteristically consists of pastures for grazing by sheep and cattle. Large amounts of nitrogen are needed for high production of grasses, grain crops, and leguminous crops which are then consumed by sheep and cattle. In New Zealand up to the equivalent of 25 ewt. of nitrogen fertilizer per acre per year have been fixed by clover and its associated nodule bacteria. “Effectively nodulated legumes can convert more that 400 lb. of nitrogen per acre per annum from the air” (Hastings et at., 1966). Since the practice of fertilizing large areas of pastureland acreage would be prohibitively expensive, legumes, which are capable through their symbiotic relationship with their corresponding nodule bacteria, to convert nitrogen from the air, are the cheapest and most practical means of providing the necessary nitrogen to the soil for use by all plants.
For some years now the practice of inoculating legume seed with strains of rhizobia has been carried out. It is therefore of primary importance to have a good knowledge of the strains of Rhizobium which are to be used as the inoculants. It is well known that strains of Rhizobium vary in their ability to fix nitrogen. Much time, energy and money may be lost when Rhizobium, which for any reason, are ineffective, i.e. do not fix adequate quantities of nitrogen.
The objective of this survey was to study some aspects of the Rhizobium bacteria associated with Trifolium repens, and to try to determine the efficiency of a range of strains of these particular nodule bacteria. The cataloguing of a number of properties of the strains under study may be of value as a guide to the selection of strains which will be most effective in any given set of conditions.||en