[Studies on the effects of atrazine and simazine on the N-binding bacteria Azotobacter and Beijerinckia in the ferralitic soils of Cuba].

In two Cuban locations (Santiago de las Vegas and Jovellanos) the effect was investigated of increasing atrazin and simazin applications (0, 4, 8, 16 kg/ha) to the number of Azotobacter and Beijerinckia colonies in weakly ferrallitic soils 7 and 15 days after their application during the rainy and dry seasons. The results were as follows: 1. The number of the Beijerinckia colonies is higher in all variants than that of Azotobacter. 2. Beijerinckia and Azotobacter are stimulated up to 7 days, partly also up to 15 days, after application of the triazins. Atrazin exhibits a stronger and more lasting effect than simazin, and Azotobacter are influenced more strongly than Beijerinckia. 3. This stimulation can be adduced with a high degree of probability to the inhibition of organisms which have an antagonistic effect on N-binding bacteria.