DESTRUCTION OF C-14-LABELED AND N-15-LABELED AMINO-ACIDS AND NUCLEIC BASES IN SOIL AND THE SUPPLY OF THEIR TRANSFORMATION PRODUCTS TO PLANTS

The destruction of amino acids (glycine and alanine) and nucleic bases (uracil) in soil was evaluated according to the mineralization losses of tracer C-14 occupying a certain position in the molecule. Carbon of carboxyl groups of amino acids was lost most rapidly, carbon of the pyrimidine ring of uracil somewhat more slowly, and carbon of the methylene group of glycine even more slowly. Microorganisms play a major role in the decomposition of both amino acids and also nucleic bases. The losses of nitrogen from different parts of the plow horizon which were detected experimentally are caused mainly by the descending migration of nitrates, which form in the process of mineralization of amino acids and uracil labeled with N-15. In the first year after the experiment was set up, the ratio of tracer carbon and nitrogen which entered the plants averaged about 1:300, which is indirect proof that the major portion of the tracer nitrogen which entered the plants was mineralized beforehand in the soil.