Sewage sludge biochar alters root colonization of mycorrhizal fungi in a soil cultivated with corn

Abstract

Sewage sludge biochar (SSB) has demonstrated a large potential to improve soil quality, availability of nutrients, particularly phosphorus (P), and increase crop productivity. There is a lack of information on the effect of P from SSB on the soil microbiota, especially on arbuscular mycorrhizal fungi. Six treatments were arranged in randomized blocks, with four replicates: 1) Control - without any amendments; 2) Mineral fertilization with NPK; 3) Biochar prepared at 300 °C (BC300); 4) Biochar prepared at 500 °C (BC500); 5) BC300 + NPK; 6) BC500 + NPK. Amendments were applied in two consecutive harvests. Microbial biomass carbon (MBC), percentage of mycorrhizal colonization (MC) and easily extractable glomalin-related soil protein (EEG) of soil mycorrhizal fungi were evaluated in all treatments. Amendment with BC300 resulted in an increase in MBC, while all treatments resulted in an increase in the colonization of corn roots by AMF. Consequently, SSB stimulated the synthesis and excretion of EEG from the soil. Biochar, NPK mineral fertilizer and their combinations increased MC in corn compared to the control. However, no additive effects of SSB and NPK addition were observed.