Establishment of homogeneous zones in a soil of alluvial origin

ABSTRACT Soils have the ability to maintain plant growth and biological activity due to their physical and chemical properties. The aim of this study was to observe the spatial distribution of some chemical properties of the soil, such as pH, organic matter (OM), electrical conductivity (EC), effective cation exchange capacity (ECEC), sulfur (S) and aluminum (Al) content and to establish zones with homogeneous chemical characteristics using the MULTISPATI-PCA technique and the fuzzy c-means algorithm. The study area was located in the Tundama and Sugamuxi Valleys (Boyacá, Colombia) with an area of 8,017 ha. Chemical properties such as pH, OM, EC, S, Al, and ECEC were indicators of the chemical degradation of these soils. Four homogeneous zones were identified. The first zone represents areas with acidity and excessive sulfur, with a pH of 4.54, 15.88% OM, 3.19 dS m-1 EC, 2.47 meq 100 g-1 Al and 365.59 meq 100 g-1 S. In contrast, the second zone represents areas with a high self-neutralizing capacity, with a pH of 5.98, 4.22% OM, 0.75 dS m-1 EC, 0.20 meq 100 g-1 Al and 44.64 meq 100 g-1 S. Zone three showed a high similarity with the first two, except for its EC and S contents. Finally, zone four showed similarity with the first, except in OM, EC and S contents. These data show that S and EC influenced the homogeneous zones because the soils in this area are called acid sulfate soils.摘要：土壤凭借其物理与化学特性，具备维持植物生长及生物活动的能力。本研究旨在观测土壤部分化学属性的空间分布特征，包括pH值、有机质（organic matter, OM）、电导率（electrical conductivity, EC）、有效阳离子交换量（effective cation exchange capacity, ECEC）、硫（sulfur, S）及铝（aluminum, Al）含量，并借助MULTISPATI-PCA技术与模糊c均值聚类算法，划分出化学特性均一的土壤分区。本研究试验区位于哥伦比亚博亚卡省的图丹马与苏加穆西山谷，总面积为8017公顷。上述pH、OM、EC、S、Al及ECEC等化学属性，可作为该区域土壤化学退化的表征指标。研究共划分出4个均一土壤分区：第一分区为酸性且硫含量过高的区域，其pH值为4.54、有机质含量15.88%、电导率3.19 dS·m⁻¹、铝含量2.47 meq·100g⁻¹、硫含量365.59 meq·100g⁻¹；与之相对，第二分区为土壤自中和能力较强的区域，其pH值为5.98、有机质含量4.22%、电导率0.75 dS·m⁻¹、铝含量0.20 meq·100g⁻¹、硫含量44.64 meq·100g⁻¹；第三分区与前两个分区具有较高相似性，仅在电导率与硫含量上存在差异；第四分区则与第一分区相似，仅在有机质、电导率及硫含量上有所不同。研究数据表明，硫含量与电导率是影响该区域均一分区划分的关键因素，这是由于该区域的土壤属于酸性硫酸盐土壤（acid sulfate soils）。