Automation of the Water-drop Method of Soil Aggregate Stability Analysis.

The water-drop method is a long established means of soil aggregate stability analysis. A major drawback of this method, however, is that it requires manual observation of aggregate breakdown and manual count of the number of water drops required to disperse a soil aggregate, which makes the method both time consuming and error prone. To avoid this drawback, we propose a procedure that utilizes digital observation of aggregate breakdown and electronic recording of water-drop count. In this procedure, water drops from a Marriott tube pass through an electronic device which records the passage of each drop. The impact of the water drops on the soil aggregate is digitally recorded with a camcorder. From the drop count and aggregate breakdown records, it is possible to determine the number of water drops that strike an aggregate until it is dispersed. This procedure was evaluated using a total of 80 soil aggregates obtained from the A-horizon of four different soils. The study determined the number of 4.2-mm diameter water drops required to destroy a 6-mm aggregate pre-moistened to a matric suction of 10 kPa until it passed through a 2.8-mm sieve. The process was replicated thrice for each soil type. The repeatability of the results was assessed based on the respective stand errors of the number of water drops that destroyed aggregates of each soil type.