Structural soil quality related to microbiological parameters in sugarcane

Abstract Sugarcane crop conventional tillage has been replaced by deep soil preparation with few studies about its effect on soil quality and sustainability. The aim of this study was to assess structural volumes ina dystrophic Red-Yellow Latosol subjected to conventional tillage (CT) and deep localized soil tillage (DLST) to verify how the microbiological parameters were affected. The study was conducted in a soil derived from the Caiuá Sandstone formation in Brazil. Four trenches were dug for each soil tillage system to describe the cultural profile and evaluate carbon microbial biomass (CMB) and nitrogen (NMB), basal respiration (BR), and metabolic quotient (qCO2). CT profiles exhibited a predominance of cracked soil volumes, medium-sized and large compact clods with some porosity, and continuous volumes with no cracks and of intermediate porosity. DLST profiles were predominantly free-soil volume with no cohesion and porous in appearance, and compact, cohesive volumes with no porosity visible. The highest levels of CMB and NMB were in the cracked soil under CT. Higher microbial activity indicated by BR and qCO2 were in the free powdery soil under DLST. Soil pulverization caused by DLST could cause serious consequences on soil functionality, boosting erosion, and metabolic stress in the microbiota.摘要 甘蔗作物的常规耕作（conventional tillage, CT）已逐步被深整地模式替代，但目前针对其对土壤质量与可持续性影响的研究仍较为匮乏。本研究以巴西凯奥阿砂岩地层发育的贫瘠型红黄色砖红壤（dystrophic Red-Yellow Latosol）为研究对象，对比常规耕作（CT）与局部深层土壤耕作（deep localized soil tillage, DLST）两种处理下的土壤结构体积特征，明确耕作方式对土壤微生物学参数的影响。试验针对每种耕作系统开挖4个剖面坑，用于描述土壤剖面并测定微生物生物量碳（carbon microbial biomass, CMB）、微生物生物量氮（nitrogen microbial biomass, NMB）、基础呼吸（basal respiration, BR）及代谢商（qCO₂）。常规耕作剖面以开裂结构体、中大型紧实土块（伴少量孔隙）以及无裂缝、中等孔隙度的连续土体为主；局部深层耕作剖面则以无黏结性、外观疏松的游离土体，以及紧实无可见孔隙的黏结性土体为主。常规耕作下开裂土壤的微生物生物量碳、氮含量最高；局部深层耕作的松散粉状土壤则表现出更高的微生物活性，具体体现为基础呼吸与代谢商水平更高。局部深层耕作引发的土壤粉碎作用可能对土壤功能造成严重负面影响，加剧土壤侵蚀，并提升微生物群落的代谢胁迫。