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Title: HEMC: A sensitive aggregate stability method for soil quality evaluation

Author
item Iliasson, Amrax
item Huang, Chi Hua
item Skidmore, Edward
item LEVY, G L - AGRIC RES ORG, ISRAEL

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/11/2007
Publication Date: 8/15/2007
Citation: Mamedov, A.I., Huang, C., Skidmore, E., Levy, G.J. 2007. HEMC: A sensitive aggregate stability method for soil quality evaluation [abstract]. American Society of Agronomy-Crop Science Society of America-Soil Science of America International Annual Meeting Abstracts, New Orleans, Louisiana. 2007 CDROM.

Interpretive Summary:

Technical Abstract: Soil aggregate stability is an important soil quality index, representing mainly soil structural stability and affecting, among others, hydraulic conductivity, seal formation, runoff, water and wind erosion. The most common method of assessing aggregate stability is wet sieving where aggregate stability is expressed by the mean weigh diameter (MWD) of the sieved fractions. However, no good correlation has thus far been found between MWD and hydraulic conductivity, infiltration (or runoff) rate and soil erosion. An alternative method for determining aggregate stability is the High Energy Moisture Characteristic (HEMC) procedure, that has been found to be a useful for detecting even small differences in the stability of aggregates from various soils. In this method, the wetting process of the aggregates is accurately controlled, and the energy of hydration and entrapped air are the main forces responsible for aggregate breakdown. An index of aggregate susceptibility to slaking on a relative scale of zero to one, termed stability ratio (SR), is obtained by quantifying differences in moisture characteristic curves (at 0-50 cm tension) for fast and slow wetting. We have studied aggregate stability with the HEMC method from a large number (> 200) of soils (i) from different regions (humid, arid); (ii) varying in their inherent properties (e.g., clay mineralogy, texture, organic matter content); (iii) under different conditions prevailing in the soil (salinity, sodicity, redox potential, type of tillage, antecedent moisture); and (iv) subjected to the addition of different amendments (polymers, gypsum, manure). We have obtained close relationships between the SR and infiltration rate, runoff, and eroded sediments for the soils studied. Furthermore, data obtained from detailed analysis of the HEMC results provide valuable information on inter- and intra- aggregate porosities which could be useful in better understanding of transport processes in the soil (near saturation). Linking the HEMC data with aggregate size distribution and dry aggregate stability (obtained from soil aggregate crushing energy meter, SACEM) could aid in the assessment of erosion processes by water and wind (environmental quality).