Water-stable soil aggregate assessment

Authors: Mikha, Maysoon; WILLS, SKYE - Natural Resources Conservation Service (NRCS, USDA)

Submitted to: Soil Science Society of America Special Publication Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 6/15/2020
Publication Date: 8/15/2021
Citation: Mikha, M.M., Wills, S. 2021. Water-stable soil aggregate assessment. In: Karlen, D.L., Stott, D.E., Mikha, M.M., editors. Soil Health Series: Volume 2 Laboratory Methods for Soil Health Analysis. Madison, WI: Soil Science Society of America. p. 52-68.

Interpretive Summary: A soil aggregate is defined as “a naturally occurring cluster or group of soil particles in which the forces holding the particles together are much stronger than the forces between adjacent aggregates”. Soil structure is defined as how the soil particles (sand, silt, and clay) are arranged and bound by organic and inorganic materials to form different size aggregate classes. Soil structure stability depends on soil aggregates that remain stable and intact when subjected to stress such as anthropogenic activity (tillage practices) or environmental sources drying-rewetting and freezing-thawing). Soil aggregation is one of the important soil structural properties that mediates many soil physical, chemical, and biological processes related to soil health and land sustainability. Soil aggregate size distribution is important because as the macroaggregates increase in size, the soil susceptibility to wind erosion decreases. Under field conditions and due to irrigation or rainfall events, the unstable dry soil macroaggregate may slake and the detached microaggregates and clay structure may fill soil pores making them narrow or disappear. Therefore, the size of soil aggregates following water destruction is an important soil parameter that required evaluation. In addition, unstable surface aggregates can lead to the formation of crusts (undesirable soil structure) that inhibit water infiltration and air movement into the soil and could affect seed germination. Over decades, researchers, extension agents, and producers realized the importance of maintaining soil structure stability to enhance land sustainability and soil health. The objective of this chapter is to present a modified version of a multiple sieve method for soil aggregate evaluation. This chapter also contains the schematic diagram of the apparatuses for easy procedure adaptation.

Technical Abstract: N/A