Chemical fumigation alters soil carbon and nitrogen dynamics in soils amended with substrates of contrasting carbon availability

Chemical fumigation is used to reduce soil-borne diseases in agricultural production systems; however, soil carbon (C) and nitrogen (N) dynamics may also be affected. This study investigated the effects of chemical fumigation and substrate C availability on soil respiration, soil nitrous oxide (N2O) production, and soil inorganic N concentrations under controlled conditions over 128 days. This study consisted of a 3 x 3 factorial arrangement of three fumigant treatments (fumigation with chloropicrin, metam sodium, or no fumigation) and three soil amendment treatments (amendment with young barley, mature barley, or no amendment). In soils amended with young barley, chemical fumigation delayed the maximum rate of soil respiration and N2O production by five days compared to the amended non-fumigated soil. Additionally, chloropicrin fumigation decreased cumulative soil respiration in amended soils, regardless of substrate C availability, compared to non-fumigated soil. Chemical fumigation used alone or combined with young barley amendments significantly inhibited nitrification compared to non-fumigated soil, whereas amendment with mature barley resulted in N immobilization, regardless of chemical fumigation. This study demonstrated that chemical fumigation significantly affected soil C and N dynamics in soils amended with high and low available C substrates, indicating decreased microbial activity and significant implications for soil function.