The expansion of agricultural frontiers has increased the use of sandy soils as cropping areas; however, the water-retention capacity (WRC) of the soil is a crucial factor. Thus, fast and accurate methodologies, such as spectroscopy, have gained importance to identify physical-hydric and other attributes related to the WRC. Some theories indicate the micromorphometry of particles is an important factor in sandy soils. This study (I) investigated the WRC of sandy soils from distinct geologic formations and the influence of particle micromorphometry on the WRC; (II) evaluated the sensitivity of Vis–NIR and MIR spectra to characterise physical-hydric attributes and particle micromorphometry; and (III) quantified physical-hydric attributes of sandy soils from their physical attributes, particle micromorphometric indices, and the visible-near infrared-mid infrared (Vis–NIR-MIR) spectra. We determined the values of field capacity (FC), permanent wilting point (PWP), available water (AW), clay, sand, silt, sand fractions, and OM as well as the micromorphometric indices and Vis–NIR and MIR reflectance of 29 sandy soil profiles. Soil attributes were correlated with each other and with the Vis–NIR and MIR spectra to understand their relationship with the WRC. The correlation and the principal component analyses (PCA) were performed to understand the relationship between Vis–NIR and MIR spectra and sand grain micromorphometry. Mathematical models were developed to estimate FC, PWP, and AW using soil attributes, micromorphometry, Vis–NIR, and MIR as predictor variables. Roughness of sand particle greatly influenced the WRC of sandy soils. The MIR region showed high sensitivity to identify different WRC patterns and particle micromorphometry in sandy soils. The Vis–NIR and MIR spectra presented high accuracy to predict FC and PWP of sandy soils. The mathematical models that used soil attributes + micromorphometry presented excellent calibration parameters; however, they did not show accuracy in the validation set.

中文翻译：

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Vis-NIR-MIR 检测砂粒微形态及其对保水性的影响

农业边界的扩大增加了沙土作为种植区的用途；然而，土壤的保水能力（WRC）是一个关键因素。因此，光谱学等快速准确的方法在识别与 WRC 相关的物理水和其他属性方面变得越来越重要。一些理论表明，颗粒的微观形态是沙质土壤中的一个重要因素。本研究 (I) 调查了来自不同地质构造的沙质土壤的 WRC 以及颗粒微形态测量对 WRC 的影响；(II) 评估 Vis-NIR 和 MIR 光谱表征物理水属性和粒子微观形态学的灵敏度；(III) 根据沙土的物理属性、颗粒微观形态指标量化沙土的物理含水属性，和可见-近红外-中红外（Vis-NIR-MIR）光谱。我们确定了田间持水量 (FC)、永久萎蔫点 (PWP)、有效水 (AW)、粘土、沙子、淤泥、沙子分数和 OM 的值，以及 29 的微形态指数和 Vis-NIR 和 MIR 反射率沙质土壤剖面。土壤属性相互关联，并与 Vis-NIR 和 MIR 光谱相关，以了解它们与 WRC 的关系。进行相关性和主成分分析 (PCA) 以了解 Vis-NIR 和 MIR 光谱与砂粒微观形态学之间的关系。使用土壤属性、微形态测量、Vis-NIR 和 MIR 作为预测变量，开发了数学模型来估计 FC、PWP 和 AW。砂粒的粗糙度对砂土的WRC影响很大。MIR 区域对识别沙质土壤中不同的 WRC 模式和颗粒微观形态具有很高的敏感性。Vis-NIR 和 MIR 光谱对预测沙质土壤的 FC 和 PWP 具有很高的准确性。使用土壤属性+微观形态的数学模型提供了出色的校准参数；但是，它们在验证集中没有显示出准确性。