Soil structure in terms of the spatial arrangement of pores and solids is highly relevant for most physical and biochemical processes in soil. While this was known for a long time, a scientific approach to quantify soil structural characteristics was also missing for a long time. This was due to its buried nature but also due to the three-dimensional complexity.

During the last two decades, tools to acquire full 3D images of undisturbed soil became more and more available and a number of powerful software tools were developed to reduce the complexity to a set of meaningful numbers. However, the standardization of soil structure analysis for a better comparability of the results is not well developed and the accessibility of required computing facilities and software is still limited. At this stage, we introduce an open-access Soil Structure Library (https://structurelib.ufz.de/, last access: 22 July 2022) which offers well-defined soil structure analyses for X-ray CT (computed tomography) data sets uploaded by interested scientists. At the same time, the aim of this library is to serve as an open data source for real pore structures as developed in a wide spectrum of different soil types under different site conditions all over the globe, by making accessible the uploaded binarized 3D images. By combining pore structure metrics with essential soil information requested during upload (e.g., bulk density, texture, organic carbon content), this Soil Structure Library can be harnessed towards data mining and development of soil-structure-based pedotransfer functions.

In this paper, we describe the architecture of the Soil Structure Library and the provided metrics. This is complemented by an example of how the database can be used to address new research questions.