Specific antibiotics and nematode trophic groups agree in assessing fungal:bacterial activity in agricultural soil

There are no methods at hand with a long and proven record for assessing the relative contribution of fungi and bacteria to decomposer activity in soil. Whereas a multitude of methods to determine fungal and bacterial biomass are available, activity assays traditionally relied on the substrate-induced respiration (SIR) inhibition approach. Here we compare fungal contribution to the microbial active biomass assessed by the SIR inhibition method with the contribution of fungal-feeding nematodes to the microbial-feeding nematode community. Four cultivation systems on the same soil that differ in carbon inputs with a factor two ranked exactly the same with the two methods. A conventionally farmed rotation with low organic input had the lowest fungal fraction, while three organically farmed soils ranked higher.