The effect of 2,4‐dichloro‐6‐(o‐chloroanilino)‐s‐triazine (dyrene) and manganese ethylene bisdithiocarbamate (maneb) at 0, 15, 60, 240, and 960 ppm on nitrification of 100 ppm applied NH4‐N, and on ammonification of soil nitrogen, and the degradation of these fungicides, were studied in a lateritic clay and a fertile loam incubated at 24C for 16 weeks.Inhibition of nitrification by the fungicides was lesser and of shorter duration in the rapidly nitrifying loam than in the slow nitrifying lateritic soil. The chemicals inhibited the ammonia oxidizing bacteria but not the nitrite oxidizing bacteria. Maneb was several times more toxic to the nitrifying organisms than dyrene, and its effect lasted even after the chemical was degraded. Ammonification was inhibited only at 960 ppm of the fungicides. There was no synergistic effect with regard to inhibition of nitrification or ammonification when the soil received both the fungicides. The fungicides were degraded faster in the rapidly nitrifying soil than in the slow nitrifying soil. Maneb was decomposed earlier than dyrene.
A virus (BVBMV) capable of inciting mild mosaic and vein-banding symptoms on various hosts was isolated from field beans (Phaseolus vulgaris L.) growing in experimental plots. The causal agent was transmitted by mechanical means as well as via aphids. The results of transmissibility, serology, host range and physical property studies indicate that the virus is a strain, possibly a new one, of the common cucumber mosaic virus (CMV) complex.
Changes in soil microorganisms following applications of 2,4-dichloro- 6-(o-cloroaniline)-s-triazine (Dyrene) and manganese ethylene bisdithiocarbamate (Maneb) at 0, 60, 240, and 960 ppm to the acid lateritic Humatas clay and the alkaline fertile San Anton loam incubated at 23° ± 1°C were studied for 18 months in the laboratory. In general, bacterial numbers increased and actinomycetes and fungi decreased especially at higher concentrations of the chemicals. The bacterial increase disappeared at the 10-month count but persisted longer at the 960 ppm rate of Maneb. Bacteria seem to be the principal microorganisms responsible for degradation of these fungicides in the soil. Maneb caused qualitative as well as quantitative changes in the fungal population. Microorganisms in the two soils differed in their response to the chemical treatment. Inhibition of the microorganisms was offset by inoculation with fresh soil.
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