Adding 5 nematodes per gram of dry soil to the petroleum-contaminated soil with a             water content of 50% and a temperature of 22C, and on this basis adding 1% biochar Site             4
The primer pair used to amplify the V3-V4 hypervariable regions of                 the bacterial 16S rRNA gene was 341F(CCTACGGGNGGCWGCAG)                 821R(GGACTACHVGGGTATCTAAT)