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After one hour the numbers of nematodes in the tube of test solutions were counted and attractivity was judged by this number. The best condition was observed at 0.02M concentration of the test solution and optimum pH range of 7 to 8. Of 20 amino acids tested, L-leucine, L-lysine, L-phenylalanine and L-tyrosine were effective. Twenty-eight esters of amino acids were examined and the attractiveness of L-ornithine ethyl ester, L-valine methyl ester and L-aspartic acid (3-alkyl esters was observed.j -Propyl, isopropyl and butyl L-aspartate were also attractive. Dialkyl, N-alkyl, N-tosyl aspartate and glutamate had no attractivity.Ammonium chloride was synergistic with these active compounds, but ammonium nitrate and hydroxide were not.Lactic acid had the attractivity, but did not show additional activity with these active compounds.

Several isothiocyanates were synthesized and their inhibitory effects upon soil nitrifica tion were examined. Some aryl isothiocyanates, such as 2,4-and 2,5-dichlorophenyl isothiocyanates, showed high activities. 21) H. Omura, Personal Communication.

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