Improving Latin American Soil Information Database for Digital Soil Mapping enhances its usability and scalability

Abstract

Abstract. Spatial soil databases can help model complex phenomena in which soils are decisive, for example, evaluating agricultural potential or estimating carbon storage capacity. The Soil Information System for Latin America and the Caribbean, SISLAC, is a regional initiative promoted by the FAO's South American Soil Partnership to contribute to the sustainable management of soil. SISLAC includes data coming from 49,084 soil profiles distributed unevenly across the continent, making it the region's largest soil database. However, some problems hinder its usages, such as the quality of the data and its high dimensionality. The objective of this research is twofold. First, to evaluate the quality of SISLAC and its data values and generate a new, improved version that meets the minimum quality requirements to be used by different interests or practical applications. Second, to demonstrate the potential of improved soil profile databases to generate more accurate information on soil properties, by conducting a case study to estimate the spatial variability of the percentage of soil organic carbon using 192 profiles in a 1473 km2 region located in the department of Valle del Cauca, Colombia. The findings show that 15 percent of the existing soil profiles had an inaccurate description of the diagnostic horizons. Further correction of an 4.5 additional percent of existing inconsistencies improved overall data quality. The improved database consists of 41,691 profiles and is available for public use at https://doi.org/10.5281/zenodo.6540710 (Díaz-Guadarrama, S. & Guevara, M., 2022). The updated profiles were segmented using algorithms for quantitative pedology to estimate the spatial variability. We generated segments one centimeter thick along with each soil profile data, then the values of these segments were adjusted using a spline-type function to enhance vertical continuity and reliability. Vertical variability was estimated up to 150 cm in-depth, while ordinary kriging predicts horizontal variability at three depth intervals, 0 to 5, 5 to 15, and 15 to 30 cm, at 250 m-spatial resolution, following the standards of the GlobalSoilMap project. Finally, the leave-one-out cross-validation provides information for evaluating the kriging model performance, obtaining values for the RMSE index between 1.77 % and 1.79 % and the R2 index greater than 0.5. The results show the usability of SISLAC database to generate spatial information on soil properties and suggest further efforts to collect a more significant amount of data to guide sustainable soil management.

Guatemala soil organic carbon database (GTMSOC)

“…This new database is an important contribution to public access to SOCS‐related variables. Global and regional compilations such as WoSIS and SISLAC contain the same 22 soil profiles for Guatemala, with nine duplicates documented in Díaz‐Guadarrama et al (2022). We recognize that the vertical section of the soil may be small because only the 0–30 cm depth is addressed, but the availability of 902 new sites for this stratum significantly contributes to the population of soil information in the geographic space of Guatemala.…”

“…On a global scale, we can mention The World Soil Information Service (WoSIS) (Batjes et al, 2017) with 196,498 soil profiles in 173 countries. In the Latin American and Caribbean (LAC) region, the Soil Information System for Latin America and the Caribbean (SISLAC) (Global‐Soil‐Partnership, 2013) recently improved by Díaz‐Guadarrama et al (2022), provides information on 41,691 soil profiles for 29 countries, being the most extensive collection in the LAC region. In similarity to this work, there are efforts at the country level within the LAC region, such as The Chilean Soil Organic Carbon database (CHLSOC) (Pfeiffer et al, 2020) and The Harmonized Soil database of Ecuador (HESD) (Armas et al, 2022).…”

Harmonized Soil Database of Ecuador (HESD): data from 2009 to 2015

“…Over the last few years, there has been a growing focus on improving the quality and quantity of soil data as well as access to soil data and information (Díaz-Guadarrama et al, 2022;Smith et al, 2022;Pfeiffer et al, 2020;Orgiazzi et al, 2018;Hengl et al, 2017). Particularly, these efforts have endeavored to increase access to harmonized products containing comparable and consistent datasets.…”