Premium
Validation of water sorption‐based clay prediction models for calcareous soils
Author(s) -
Arthur Emmanuel,
Razzaghi Fatemeh,
Moosavi Ali Akbar
Publication year - 2017
Publication title -
journal of plant nutrition and soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 87
eISSN - 1522-2624
pISSN - 1436-8730
DOI - 10.1002/jpln.201700001
Subject(s) - sorption , soil water , soil science , water content , clay minerals , kaolinite , calcareous , salinity , relative humidity , mineralogy , environmental chemistry , chemistry , environmental science , geology , adsorption , geotechnical engineering , paleontology , organic chemistry , oceanography , physics , thermodynamics
Abstract Soil particle size distribution (PSD), particularly the active clay fraction, mediates soil engineering, agronomic and environmental functions. The tedious and costly nature of traditional methods of determining PSD prompted the development of water sorption‐based models for determining the clay fraction. The applicability of such models to semi‐arid soils with significant amounts of calcium carbonate and/or gypsum is unknown. The objective of this study was to validate three water sorption‐based clay prediction models for 30 calcareous soils from Iran and identify the effect of CaCO 3 on prediction accuracy. The soils had clay content ranging from 9 to 61% and CaCO 3 from 24 to 97%. The three water sorption models considered showed a reasonably fair prediction of the clay content from water sorption at 28% relative humidity (RMSE and ME values ranging from 10.6 to 12.1 and −8.1 to −4.2, respectively). The model that considers hysteresis had better prediction accuracy than the other two that do not. Moreover, the prediction errors of all three models arose from under‐prediction of the clay content. The amount of hygroscopic water scaled by clay content decreased with increasing CaCO 3 content. The low organic carbon content of the soils and the low fraction of low‐activity clay minerals like kaolinite suggested that the clay content under‐predictions were due to large CaCO 3 contents. Thus, for such water‐sorption based models to work accurately for calcareous soils, a correction factor that considers the reduction of water content due to large CaCO 3 content should be included.