Interactive effect of climate factors, biochar and insecticide chlorpyrifos on methane consumption and microbial abundance in a tropical Vertisol

Climate change may increase the pest infestation leading to intensive use of insecticides. However, the effect of insecticide and climate factors on soil methane (CH4) consumption is less understood. A laboratory experiment was carried out to evaluate the effect of temperature (15 °C, 35 °C, and 45 °C), moisture holding capacity (MHC) (60%, 100%), biochar (0%, 1%) and chlorpyrifos (0 ppm, 10 ppm) on CH4 consumption and microbial abundance in a tropical Vertisol of central India. Methane consumption rate k (ng CH4 consumed g−1 soil d−1) varied from 0.065 ± 0.005 to 0.608 ± 0.018. Lowest k was in 15 °C-60% moisture holding capacity (MHC)-no biochar and with 10 ppm chlorpyrifos. Highest k was in 35 °C-100% MHC-1% biochar and without (0 ppm) chlorpyrifos. Cumulative CO2 production (ng CO2 produced g−1 soil d−1) varied from 446 ± 15 to 1989 ± 116. Both CH4 consumption and CO2 production peaked in the treatment of 35 °C-100% MHC-1% biochar. Chlorpyrifos inhibited CH4 consumption irrespective of treatments. Abundance of 16S rRNA of eubacteria (× 106 g−1 soil) varied from 2.33 ± 0.58 to 85.67 ± 7.00. Abundance of 16S rRNA genes representing Actinomycetes (× 104 g−1 soil) varied from 7.67 ± 1.53 and pmoA gene (Methanotrophs) (× 105 g−1 soil) varied from 1.23 ± 0.59 to 34.33 ± 6.51. Chlorpyrifos inhibited abundance of heterotrophic bacteria and methanotrophs but stimulated actinomycetes. Biochar stimulated the CH4 consumption, CO2 production and microbial abundance. Study highlighted that use of chlorpyrifos under climate change factors may inhibit CH4 consumption but the use of biochar may alleviate the negative effect of the chlorpyrifos.