Effect of pyrimorph on soil enzymatic activities and respiration

The effects of a novel fungicide, pyrimorph, on the soil enzyme activities and respiration in upland soil were studied over a period of 90 days. Pyrimorph ranged from 0.5 to 150 mg kg−1 accelerated the activities of catalase, invertase and dehydrogenase in soil. Urease activities in soil treated with 50–150 mg kg−1 pyrimorph were also stimulated significantly within the first 45 days, but inhibited obviously from 60 to 90th day of incubation. Among the four enzymes, dehydrogenase was most sensitive to pyrimorph, and the highest activities in samples treated by pyrimorph with 100 or 150 mg kg−1 were 5-and 5.3-fold to that of the control, respectively. Soil respiration was stimulated within the first 14 days, and then from the 21th day, there were no distinct difference between the treated samples and the control. All the results demonstrated that pyrimorph at the lowest dose (0.5 mg kg−1) would not exhibited any toxicological threat to soil enzymes and soil respiration. Moreover, higher concentrations in a range 5–150 mg kg−1 displayed an activation effect on soil enzymes and soil respiration, yet a certain potential threat to soil urease in the last stage of incubation.

► Pyrimorph accelerated the activities of soil catalase, invertase and dehydrogenase.
► Pyrimorph had potential threat to soil urease in the last stage of incubation.
► Pyrimorph had the highest positive effect on dehydrogenase.
► Pyrimorph increased soil respiration within the first 14 days.
► The main effects of pyrimorph on soil enzymes and soil respiration were positive.