preparations that contain soil microorganisms which are beneficial to agricultural plants. When bacterial fertilizers are applied to the soil, biochemical processes are strengthened and the root nourishment of the plants is improved. In the USSR the bacterial fertilizers which are used are nitragin, azotobakterin, and fosforobak-terin.
Nitragin is a fertilizer for leguminous plants. It is made from active nodule bacteria, a specific bacterium for each species of legume; these bacteria are reproduced in a substrate which is sterilized and enriched with organic substance. The first preparation was obtained in 1896 in Germany. Later it was made in Russia, France, Czechoslovakia, and other countries. According to the standards in effect in the USSR, 1 gram of nitragin must contain not less than 70 million cells of nodule bacteria for lupine, soybeans, bird’s-foot, and peanuts, and not less than 300 million for the remaining leguminous plants. As the bacteria penetrate the root hairs, they form nodules on the roots of the legumes. As they increasingly reproduce in the tissues of the nodule, they fix the atmospheric nitrogen, a significant part of which is assimilated by the plant. Nitragin is most effective in combination with organic and mineral fertilizers.
Azotobakterin (azotogen) is made from active cultures of the microorganism Azotobacter. Soil (or turf) azotobakterin is different from agar azotobakterin. According to Soviet standards in effect, 1 gram of soil azotobakterin must contain at least 50 million Azotobacter cells. Azotobacter actively grows only in fertile soils with many organic substances. It improves the nitrogen nourishment and the growth of the plant.
Fosforobakterin is a white, light-gray, or yellow powder, which contains a large number (8.5–16 billion in 1 gram) of spores of microorganisms which have the heightened capability of transforming organic phosphorus compounds into a fixed form for the plants. It is most effective in a base of organic and mineral fertilizers.
Bacterial fertilizers are usually applied to the soil together with the seeds or planting material, in this case with special directions. Bacterial fertilizers cannot be stored for a long period of time, and for this reason they are prepared in quantities for one season only. They are stored in factory packing in a dry compartment at temperatures of from 0° to 10° C. Bacterial fertilizers may not be kept in a storehouse where there are airborne toxic materials. Some authors consider AMB (autochthonous microflora B) a bacterial fertilizer, but the economic advisability of using this fertilizer requires further study.
REFERENCESFedorov, M. V. Biologicheskaia fiksatsiia azota atmosfery,2nd ed. Moscow, 1952.
Dorosinskii, L. M. Bakterial’nye udobreniia—dopolnitel’noe sredstvo povysheniia urozhaia. Moscow, 1965.