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Research on Crops

Soil formation assessment using depth function of Entisols and Mollisols in Iraq


DOI: 10.31830/2348-7542.2026.ROC-1267    | Article Id: ROC-1267 | Page : 65-76
Citation :- Soil formation assessment using depth function of Entisols and Mollisols in Iraq. Res. Crop. 27: 65-76
OMAR ALSALAM, TEEBA MOBARKAH, HUSIAN A. ISA, ABDULGHAFOUR IBRAHIM HAMAD AND SANARYA SABAH MOHAMMED omar.t@coagri.uobaghdad.edu.iq
Address : University of Baghdad, College of Agriculture Engineering Sciences, Department of Soil Science and Water Resources, Baghdad, Iraq
Submitted Date : 13-11-2025
Accepted Date : 10-01-2026
Online Published:

Abstract

Soil formation is strongly influenced by the redistribution and loss of major elements such as Ca, Mg, K, and Na, processes which are controlled by parent material, weathering, and climate. The depth function (τ) provides a quantitative measure of these element changes (Fasina et al., 2021) and is a valuable tool for assessing soil weathering and horizon development. However, in Iraq, studies using geochemical indicators, particularly the depth function, to evaluate Mollisols and Entisols under varying climatic conditions are lacking. Therefore, this study was conducted to investigate the behavior of major elements through the evaluation of the depth function (τ) for Mollisols and Entisols soil horizons in Iraq as a function of climate, in addition to describing the morphological, physical, chemical, and geochemical differences of these soils. The study included two different sites: the first site is the soils of Erbil, characterized by a semi-humid climate and representing Mollisols, and the second site is the soils of Baghdad, with an arid climate and representing Entisols. Two pedons were selected for each site. The results generally showed a decrease in the major elements (Al, Si, Na, K), while the proportions of (Fe, Mg, Ca) increased in Mollisols. Differences in the distribution of the depth function (τ) for the studied soils reflect the importance of soil water balance in controlling the differences between downward leaching in Mollisols and upward evaporation of dissolved substances in Entisols. Developed soils containing the Bt clay horizon (clay accumulation horizon) were found as a result of prevailing climatic conditions with increased rainfall, which led to increased activity of leaching and loss processes and the formation of Argillic and Calcic horizons in Mollisols, in addition to dark color development and the occurrence of Melanization and Rubification in these soils. Entisols, on the other hand, did not show any clear developmental features in their horizons due to hot, dry conditions. This study confirmed the existence of variation in soil formation, attributed to differences in parent material, prevailing climate, and their influence on processes such as leaching, loss, and calcification.

Keywords

Calcareous soil pedogenic processes semi-arid semi-humid soil orders total oxides.

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