Denitrification in a chinampa soil of Mexico City as affected by methylparathion: A laboratory study

Chinampas are raised garden beds used for agriculture in the valley of Mexico since pre-Hispanic times. Large amounts of methylparathion, i.e. approximately 0.5 kg ha−1 per crop cycle, are used to control pests with an unknown effect on soil processes, such as the denitrification process. Soil was amended with nitrate (NO3−) with or without chloramphenicol known to inhibit de novo synthesis of enzymes, with or without acetylene (C2H2) known to inhibit the reduction of nitrous oxide (N2O) to dinitrogen (N2) and spiked with or without methylparathion. Methylparathion increased the N2O and N2 emissions, the NO2− concentration and removal of NO3− from soil. The NO2− concentration in the anaerobic incubation was larger when soil was conditioned aerobically <7 days compared to soil conditioned for >7 days, but no such pattern was observed for the removal of NO3−. C2H2 and/or chloramphenicol had no significant effect on NO3− removal and the NO2− concentration in the methylparathion-amended soil, but increased the NO2− concentration in unamended soil with C2H2 plus chloramphenicol compared to the other treatments. C2H2 increased the N2O emission in soil amended with or without methylparathion and with or without chloramphenicol.

► We analysed denitrification process in presence of methylparathion pesticide. ► The particular soil is a Mexican soil from plot called chinampa. ► It is situated in zone agricultural declared World Heritage site by UNESCO (1987). ► It is due to its agricultural tradition unique in the world.