Strategic tillage increased the relative abundance of Acidobacteria but did not impact on overall soil microbial properties of a 19-year no-till Solonetz

Continuous no-till (NT) farming is widely practiced in Australia, but it is prone to weed infestation. Strategic tillage (ST) can be used to effectively control weeds; however, it is unclear whether ST influences soil microbial properties. We investigated whether one- or two-time tillage events using a chisel plough influence the soil microbial properties of an acidic Solonetz with 19-year NT management. Soil samples were collected from 0–10 and 10–20\ua0cm soil depths, 1\ua0year post-ST after a chickpea crop. Microbial biomass C (MBC) and N (MBN), community-level physiological profiling (CLPP, MicroResp™) and fluorescein diacetate as an indicator of total microbial activity (TMA) were determined in soil. The composition of soil microbial communities was profiled using terminal reaction fragment length polymorphism (T-RFLP) and 16S rRNA sequencing. Detection and DNA-based quantitation of ChitinaseA, nifH, amoA, narG, nirK and nosZ genes were used to assess ST effects on soil C and N cycling. Our results show that one- and two-time chisel did not change soil MBC/MBN, TMA or CLPP. Likewise, ST did not change the composition of soil microbial communities and the abundance of genes encoding enzymes involved in key steps of C and N reactions at either soil depth. However, one-time chisel increased relative abundance of Acidobacteria RB41 and Acidobacteria iii1-15, and two-time chisel slightly increased the average C utilisation, both at 10–20\ua0cm soil depth. This suggests that even after a cropping season of chickpea, ST effects on soil microbial properties of the NT Solonetz were negligible. One- and two-time chisel could potentially address the issues associated with long-term NT without impacting overall soil microbial properties