Pedosphere 28(4): 581--596, 2018
ISSN 1002-0160/CN 32-1315/P
©2018 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Soil Bulk Density Estimation Methods: A Review
Ahmed Abed Gatea AL-SHAMMARY1,3, Abbas Z. KOUZANI1, Akif KAYNAK1, Sui Yang KHOO1, Michael NORTON1, Will GATES2
1School of Engineering, Deakin University, Geelong VIC 3216(Australia)
2Institute for Frontier Materials, Deakin University, Burwood VIC 3125(Australia)
3Soil Science and Water Resources Departments, College of Agriculture, University of Wasit, Kut 964(Iraq)
Corresponding Author:Ahmed Abed Gatea AL-SHAMMARY
      Measurement of soil bulk density is important for understanding the physical, chemical, and biological properties of soil. Accurate and rapid soil bulk density measurement techniques play a significant role in agricultural experimental research. This review is a comprehensive summary of existing measurement methods and evaluates their advantages, disadvantages, potential sources of error, and directions for future development. These techniques can be broadly categorised as direct and indirect methods. Direct methods include core, clod, and excavation sampling, whereas indirect methods include the radiation and regression approaches. The core method is most widely used, but it is time consuming and difficult to use for sampling multiple soil depths. The size of the coring cylinder used, operator experience, sampling depth, and in-situ soil moisture content significantly affect its accuracy. The clod method is suitable for use with heavy clay soils, and its accuracy is dependent on equipment calibration, drying time, and operator experience, but the process is complicated and time consuming. Excavation techniques are most commonly used to evaluate the bulk density of forest soils, but have major limitations as they cannot be used in soils with large pores and their measurement accuracy is strongly influenced by soil texture and the type of analysis selected. The indirect methods appear to have greater accuracy than direct approaches, but have higher costs, are more complex, and require greater operator experience. One such approach uses gamma radiation, and its accuracy is strongly influenced by soil depth. Regression methods are economical as they can make indirect measurements, but these depend on good, quality data of soil texture and organic matter content and geographical and climatic properties. Also, like most of the other approaches, its accuracy decreases with sampling depth.
Key Words:  measurement accuracy,direct measurement methods,gamma radiation,indirect measurement methods,regression methods,sampling depth,soil properties
Citation: Al-Shammary A A G, Kouzani A Z, Kaynak A, Khoo S Y, Norton M, Gates W. 2018. Soil bulk density estimation methods: A review. Pedosphere. 28(4): 581–596.
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