An Improved Method for Creating Moisture Release Curves in Dry Soils to Determine Mineralogical and Physical Properties.

Soil moisture release curves (MRC), which relate the amount of water in soil to its water potential, have many applications in soil physics and geotechnical engineering including determining soil water flow, specific surface area, swelling potential, and clay mineralogy and activity.  Although research showing MRC for various soils dates back more than 50 years, limitations with the measurement technique have made developing MRC time consuming and inaccurate, especially in dry soils.  Recently, an instrument was developed to create MRC for various food and pharmaceutical products.  The objective of this research was to investigate its use in soils for obtaining MRC in dry soils simply and accurately.  Several different soil types were tested in the instrument from pure sand to bentonite and smectite clays.  From the MRC of these soils, we were able to develop good correlations between actual and derived clay activity, surface area, and swelling potential.  In addition, we were able to see hysteresis in dry soil water uptake for all soils, including sand.  According to our tests, this new instrument will provide a powerful tool to investigate several soil physical properties simply and accurately.