Sulfur (S) is present mainly in organic forms in the most superficial layers of well-drained soils, despite sulfate (SO₄²⁻) being the main S-species absorbed by plants. Coupled broadcast application of lime and phosphogypsum (PG) is widely deployed as an agricultural practice to improve soil chemical properties and increase crop yields in highly weathered tropical soil areas under no-tillage system (NTS). However, the effects of large-scale application of these soil amendments to S-species distribution in soil in NTS are largely unknown. We combined S wet-chemical analysis with Synchrotron-based X-ray Absorption Near-Edge Structure Spectroscopy (XANES) to evaluate the effects of lime and PG application to S-species distribution along the soil profile (up to 150 cm). Soil samples were collected from a field-scale experiment under NTS for over 15 years. Soil was amended with lime and PG, either individually or in combination, four times during the experiment. Soil sampling was conducted 16 months after the last amendments’ application, and treatments (lime, PG and lime + PG) were compared to a control (under NTS without amendments’ application) and with soil samples from a native forest (reference for an undisturbed site). Broadcast PG application increased the contents of Ca-phosphate extractable S and pseudo-total S (microwave assisted acid digestion) contents in the deeper layers. Two peaks representing reduced and oxidized S species were detected in S K-edge XANES spectra of all treatments and NF soil. The oxidized S peak gets sharper with increase in depth, as reduced S peak intensity decreases, and fingerprint analysis suggested a greater contribution of reduced organic S species in the most superficial soil layer followed by an increase in highly oxidized S species as depth increased. Linear combination fitting analysis confirmed a greater contribution of highly oxidized S species to the total S-species as depth increased, especially in soil samples that received PG application.

尽管硫酸盐 (SO ₄ ²⁻) 是植物吸收的主要 S 物种。在免耕系统 (NTS) 下，石灰和磷石膏 (PG) 的耦合播撒应用被广泛用作农业实践，以改善土壤化学性质并提高高度风化热带土壤地区的作物产量。然而，大规模应用这些土壤改良剂对 NTS 土壤中 S 物种分布的影响在很大程度上是未知的。我们将 S 湿化学分析与基于同步加速器的 X 射线吸收近边结构光谱 (XANES) 相结合，以评估石灰和 PG 应用对沿土壤剖面（高达 150 厘米）的 S 物种分布的影响。土壤样品是从 NTS 下的田间规模试验中收集的，超过 15 年。在实验过程中，单独或结合使用石灰和 PG 对土壤进行了四次改良。在最后一次修订申请后 16 个月进行土壤取样，并将处理（石灰、PG 和石灰 + PG）与对照（在未申请修订的 NTS 下）和来自原始森林的土壤样品（未受干扰的参考）进行比较地点）。广播 PG 的应用增加了更深层的磷酸钙可萃取 S 和伪总 S（微波辅助酸消化）的含量。在 S 中检测到代表还原和氧化 S 物种的两个峰 广播 PG 的应用增加了更深层的磷酸钙可萃取 S 和伪总 S（微波辅助酸消化）的含量。在 S 中检测到代表还原和氧化 S 物种的两个峰 广播 PG 的应用增加了更深层的磷酸钙可萃取 S 和伪总 S（微波辅助酸消化）的含量。在 S 中检测到代表还原和氧化 S 物种的两个峰所有处理和 NF 土壤的K边 XANES 光谱。随着深度的增加，氧化的 S 峰变得更尖锐，因为减少的 S 峰强度降低，指纹分析表明最表层土壤中有机 S 种类减少的贡献更大，然后随着深度的增加，高度氧化的 S 种类增加。线性组合拟合分析证实，随着深度的增加，高度氧化的 S 物种对总 S 物种的贡献更大，尤其是在接受 PG 应用的土壤样品中。