Soil spectral libraries (SSLs) are being created worldwide due to their enormous potential to train machine learning algorithms that may benefit environmental and agricultural activities. Accordingly, the extent to which the different SSLs maintain their accuracy for unknown samples is important. Recently, the internal soil standard (ISS) has garnered attention in the soil spectroscopy literature, due to its capacity to rectify systematic effects during spectral measurements. Moreover, a new initiative by the Institute of Electrical and Electronics Engineers Standards Association (IEEE SA) to create an agreed-upon measurement standard and protocol for soil spectral measurements has been launched. Application of the ISS to align one spectrum with another for merging different SSLs is highly needed. This led us to postulate the necessity of evaluating the performance of spectral-based models using different large SSLs that were created following different protocols. Using the random forest (RF) algorithm, we tested four different well-known large SSLs to predict clay content. From these SSLs, two of them were created using the ISS method (GEOCRADLE and Israel) and the other two without (LUCAS and ICRAF–ISRIC). Then, three groups of soils from different regions (Israel, Czech Republic, and Brazil) were used as external test samples to examine the SSLs' performance. The SSLs that were generated following the ISS protocol yielded the best performance in a group of samples that utilized the same method. It was concluded that using an agreed ISS such as the Lucky Bay (LB) soil sample enables a favorable way to merge SSLs.

土壤光谱库 (SSL) 正在全球范围内创建，因为它们在训练机器学习算法方面具有巨大潜力，可能有利于环境和农业活动。因此，不同 SSL 对未知样本保持其准确性的程度很重要。最近，土壤内部标准 (ISS) 在土壤光谱学文献中引起了关注，因为它能够在光谱测量期间纠正系统效应。此外，电气和电子工程师协会标准协会 (IEEE SA) 发起了一项新举措，旨在为土壤光谱测量创建一个商定的测量标准和协议。非常需要应用 ISS 将一个频谱与另一个频谱对齐以合并不同的 SSL。这导致我们假设有必要使用按照不同协议创建的不同大型 SSL 来评估基于频谱的模型的性能。使用随机森林 (RF) 算法，我们测试了四种不同的知名大型 SSL 来预测粘土含量。从这些 SSL 中，其中两个是使用 ISS 方法（GEOCRADLE 和以色列）创建的，另外两个没有（LUCAS 和 ICRAF-ISRIC）。然后，使用来自不同地区（以色列、捷克共和国和巴西）的三组土壤作为外部测试样本来检查 SSLs 的性能。按照 ISS 协议生成的 SSL 在使用相同方法的一组样本中产生了最佳性能。得出的结论是，使用商定的国际空间站（例如 Lucky Bay (LB) 土壤样本）是一种合并 SSL 的有利方式。