Abstract

Agriculture frequently applies fertilizers and pesticides to increase crop productivity and yield. Massive use of fertilizers and pollution of heavy metals and pesticides alter biogeochemical cycles in agricultural systems. The biogeochemical nitrogen cycle in soils includes nitrogen fixation, nitrification and denitrification processes that are carried out by microbial communities. The aims of this report are the analyses of the effects of fertilization, heavy metals and pesticides on the microbial communities associated with the nitrogen cycle in agricultural soils, and the bioremediation strategies of agricultural soils polluted with heavy metals and pesticides. Fertilization reduces nitrogen fixation and increases nitrification and denitrification processes. Pollution by heavy metals and pesticides generally showed negative effects on the nitrogen cycle. Specifically, microbial communities associated with nitrogen fixation and nitrification are highly susceptible to these pollutants. The bioremediation of heavy metals (Cu, Cd and Hg) and pesticides (e.g. atrazine, mancozeb, imidacloprid) has been successfully carried out in agricultural soils, restoring the nitrogen cycle.