New pedotransfer approaches to predict soil bulk density using WoSIS soil data and environmental covariates in Mediterranean agro-ecosystems

Calogero Schillaci, Alessia Perego*, Elena Valkama, Michael Märker, Sergio Saia, Fabio Veronesi, Aldo Lipani, L. Lombardo, Tommaso Tadiello, Hannes A. Gamper, Luigi Tedone, Cami Moss, Elena Pareja-Serrano, Gabriele Amato, Kersten Kühl, Claudia Dămătîrcă, Alessia Cogato, Nada Mzid, Rasu Eeswaran, Marya RabeloGiorgio Sperandio, Alberto Bosino, Margherita Bufalini, Tülay Tunçay, Jianqi Ding, Marco Fiorentini, Guadalupe Tiscornia, Sarah Conradt, Marco Botta, Marco Acutis

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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For the estimation of the soil organic carbon stocks, bulk density (BD) is a fundamental parameter but measured data are usually not available especially when dealing with legacy soil data. It is possible to estimate BD by applying pedotransfer function (PTF). We applied different estimation methods with the aim to define a suitable PTF for BD of arable land for the Mediterranean Basin, which has peculiar climate features that may influence the soil carbon sequestration. To improve the existing BD estimation methods, we used a set of public climatic and topographic data along with the soil texture and organic carbon data. The present work consisted of the following steps: i) development of three PTFs models separately for top (0–0.4 m) and subsoil (0.4–1.2 m), ii) a 10-fold cross-validation, iii) model transferability using an external dataset derived from published data. The development of the new PTFs was based on the training dataset consisting of World Soil Information Service (WoSIS) soil profile data, climatic data from WorldClim at 1 km spatial resolution and Shuttle Radar Topography Mission (SRTM) digital elevation model at 30 m spatial resolution. The three PTFs models were developed using: Multiple Linear Regression stepwise (MLR-S), Multiple Linear Regression backward stepwise (MLR-BS), and Artificial Neural Network (ANN). The predictions of the newly developed PTFs were compared with the BD calculated using the PTF proposed by Manrique and Jones (MJ) and the modelled BD derived from the global SoilGrids dataset. For the topsoil training dataset (N = 129), MLR-S, MLR-BS and ANN had a R2 0.35, 0.58 and 0.86, respectively. For the model transferability, the three PTFs applied to the external topsoil dataset (N = 59), achieved R2 values of 0.06, 0.03 and 0.41. For the subsoil training dataset (N = 180), MLR-S, MLR-BS and ANN the R2 values were 0.36, 0.46 and 0.83, respectively. When applied to the external subsoil dataset (N = 29), the R2 values were 0.05, 0.06 and 0.41. The cross-validation for both top and subsoil dataset, resulted in an intermediate performance compared to calibration and validation with the external dataset. The new ANN PTF outperformed MLR-S, MLR-BS, MJ and SoilGrids approaches for estimating BD. Further improvements may be achieved by additionally considering the time of sampling, agricultural soil management and cultivation practices in predictive models.

Original languageEnglish
Article number146609
Number of pages13
JournalScience of the total environment
Early online date19 Mar 2021
Publication statusPublished - 1 Aug 2021


  • Agriculture
  • Bulk density
  • Pedotransfer functions
  • PTFs
  • Soil carbon
  • Soil texture


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