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.

甘蔗（Saccharum spp.）是一种经济价值举足轻重的作物，主要用于蔗糖及生物乙醇的生产。在中国南方，种植于酸性土壤中的甘蔗常因土壤锰（Mn）含量过高而出现严重的叶片失绿症。然而，锰（Mn）毒害破坏土壤氮（N）循环的具体机制，尤其是氨氧化细菌（ammonia-oxidizing bacteria, AOB）与氨氧化古菌（ammonia-oxidizing archaea, AOA）在调控甘蔗硝化作用及氮素有效性方面的作用，仍有待深入探究。为填补这一研究空白，本研究开展了室内土壤培养试验与温室盆栽试验，共设置4组处理：2个氮（N）水平与2个锰（Mn）水平的交叉组合，外加空白对照（CK）。核心测定指标包括根际土壤理化性质、氨氧化细菌/古菌群落结构（通过高通量测序与定量PCR（qPCR））、硝化潜势以及甘蔗氮素吸收效率。本研究结果表明，锰毒害通过破坏氨氧化微生物群落、抑制硝化作用，损害甘蔗的氮素利用能力，为锰污染酸性土壤的氮素管理策略优化提供了理论依据。