Manganese Toxicity Impairs Soil Nitrification and Sugarcane Nitrogen Utilization by Inhibiting Rhizosphere Ammonia-Oxidizing Microorganisms
Sugarcane (Saccharum spp.) is an economically vital crop cultivated primarily for sugar and bioethanol production. In southern China, sugarcane grown in acidic soils often exhibits severe leaf chlorosis due to excessive soil manganese (Mn) levels. However, the mechanisms by which Mn toxicity disrupts soil nitrogen (N) cycling, particularly the roles of ammonia-oxidizing bacteria (AOB) and archaea (AOA) in regulating nitrification and N availability for sugarcane remain underexplored. To address this gap, we conducted laboratory soil incubation experiments and greenhouse pot trials with four treatments: two N levels crossed with two Mn levels, plus a blank control (CK). Key measurements included rhizosphere soil physicochemical properties, AOB/AOA community structure (via high-throughput sequencing and qPCR), nitrification potential, and sugarcane N uptake efficiency. These findings indicate that Mn toxicity impairs sugarcane N utilization by disrupting ammonia-oxidizing microbial communities and suppressing nitrification, providing insights for optimizing N management strategies in Mn-contaminated acidic soils.