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 cm soil depths, 1 year post-ST after a chickpea crop. Microbial biomass C (MBC) and N (MBN), community-level physiological profiling (CLPP, MicroResp (TM)) 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 cm 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.