Laboratory investigations into the effects of the pesticides mancozeb, chlorothalonil, and prosulfuron on nitrous oxide and nitric oxide production in fertilized soil

Abstract: Independent soil microcosm experiments were used to investigate the effects of the fungicides mancozeb and chlorothalonil, and the herbicide prosulfuron, on N2O and NO production by nitrifying and denitrifying bacteria in fertilized soil. Soil cores were amended with NH4NO3 or NH4NO3 and pesticide, and the N2O and NO concentrations were monitored periodically for approximately 48h following amendment. Nitrification is the major source of N2O and NO in these soils at soil moistures relevant to those observed at the field site where the cores were collected. At pesticide concentrations from 0.02 to 10 times that of a standard single application on a corn crop, N2O and NO production was inhibited by all three pesticides. Generally N2O production was inhibited by the pesticides from 10 to 62% and 20 to 98% at the lowest and highest dosages, respectively. Nitric oxide production was generally inhibited from about 5 to 47% and by 20 to 97% at the lowest and highest dosages, respectively. Nitrous oxide and nitric oxide production by nitrification was more susceptible to inhibition by these pesticides than denitrification. Production of both N2O and NO by nitrification was inhibited by as much as 99%, at the highest concentration of pesticide applied. The net production of N2O increased as soil moisture increased. The rate of NO production was greatest at the intermediate moistures investigated, between 14 and 19% gravimetric soil moisture, suggestive that nitrification is the dominant source of NO. [Copyright &y& Elsevier]