Pyrolyzed or Composted Sewage Sludge Application Induces Short-Term Changes in the Terra Rossa Soil Bacterial and Fungal Communities

The addition of compost or biochar to soils is a viable strategy to increase soil organic matter (SOM), especially if the amendments are produced from biomass wastes. The need for sustainable land management without sacrificing agricultural production is critical to alleviate negative impacts on soil quality, including loss of SOM and nutrients. Turning sewage sludge (SS) into compost or biochar can help in lowering its potential negative effects on soil and providing a viable strategy for SS management through its recycling in agriculture. The aim of this study was to evaluate the short-term impact of SS in its composted or biochar form on the fungal and bacterial communities of the Terra Rossa soil by high-throughput sequencing. A greenhouse pot trial was conducted using a 2-factor experiment consisting of amendment type (compost, biochar) and sampling time (Day 0, 30, and 60) as the main factors. The results showed no effect of SS addition on fungal and bacterial species richness, as well as a shift in relative abundance of the fungal phylum Zygomycota and bacterial phylum Firmicutes and Thermomicrobia. Both bacterial and fungal community analyses showed changes when composted sewage sludge was applied. However, only the fungal community differed from the control soil by the end of the 60-day vegetation period of Chinese cabbage.