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 (CH) 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 CH consumption and microbial abundance in a tropical Vertisol of central India. Methane consumption rate k (ng CH consumed g soil d) 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 CO production (ng CO produced g soil d) varied from 446 ± 15 to 1989 ± 116. Both CH consumption and CO production peaked in the treatment of 35 °C-100% MHC-1% biochar. Chlorpyrifos inhibited CH consumption irrespective of treatments. Abundance of 16S rRNA of eubacteria (× 10 g soil) varied from 2.33 ± 0.58 to 85.67 ± 7.00. Abundance of 16S rRNA genes representing Actinomycetes (× 10 g soil) varied from 7.67 ± 1.53 and pmoA gene (Methanotrophs) (× 10 g 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 CH consumption, CO production and microbial abundance. Study highlighted that use of chlorpyrifos under climate change factors may inhibit CH consumption but the use of biochar may alleviate the negative effect of the chlorpyrifos.