16S rRNA amplicon sequencing of the soil samples: soil SM with CF treatmnet replicate 3
DNA was subsequently amplified by polymerase chain reaction (PCR) targeting the amoA for AOB  (forward primer 1Fmod: 5'-CTGGGGTTTCTACTGGTGGTC-3' and reverse primer GenAOBR: 5'-GCAGTGATCATCCAGTTGCG -3'). To perform PCR, 12.5 L AmpliTaq Gold 360 Master Mix (Applied Biosystems, Foster City, CA, USA), 0.5 L of the forward primer, 0.5 L of the reverse primer, 9.5 L nuclease-free water and 1 L DNA extract were mixed. The first PCR cycle was set to 95C for 10 min and then 40 cycles at 95C for 30 s, 58C for 1 min  and 72C for 1 min, followed by 72C for 1 min. The PCR products were subsequently purified with Agencourt AMPure XP (Beckman Coulter) according to the given protocol. Then, the purified products were quantified with the QuantiFluor ONE dsDNA System by a Quantus Fluorometer E6167 (Promega, Madison, WI, USA).