Testing a new procedure for measuring water-stable aggregation

Aggregate stability is an important but difficult soil property to quantify and interpret. Numerous methods have been used to determine aggregate stability with varying success. This complicates the comparison among aggregate stability data. It is also difficult to obtain a consistent correlation between aggregate stability and other important soil properties such as soil erodibility or crusting potential. The objective of this study was to compare the standard Kemper and Rosenau method for measuring water-stable aggregates (WSA) with a new technique, and correlate the erosive and crusting behavior of 10 new California soils to the aggregate stabilities determined by both methods. The new method consists of determining the particle-size distribution of aggregates remaining on a 0.25-mm-diam. sieve after fast wetting, slow wetting, and stirring after prewetting. In the new technique, aggregates are sieved in alcohol instead of water. Both stability tests are simple and give reproducible estimates of aggregate stability. Coefficients of variation were <5% for both methods. However, only the stability parameters like mean weight diameter (MWD) for fast wetting and stirring after prewetting, obtained with the new method, correlate well with the erosive and crusting behavior of the test soils. For example, MWD after fast wetting was significantly correlated (r = -0.85) with splash erosion mass, but there was no significant correlation between WSA, obtained with the standard method, and splash erosion mass. In addition, the new method provides information about the stability for various conditions occurring at the soil surface as well as about the mechanisms causing stability loss.