Energy of dispersing of loamy soils to elementary particles using ultrasound

Elementary soil particles are the first soil-specific level in the soil structure hierarchy, which is also the object of the soil texture analysis. To disperse soil solids to elementary soil particles (ESP), it is necessary to break the strong bonds between particles by physical action. An effective way of physical dispersion is to treat soil suspensions with ultrasound. However, depending on the type of soil, the required energy level varies, as it is determined by the stability of the soil structure. In this work the experiment with increasing energy (from 65 to 1 101 J·mL-1) of ultrasonic dispersion at constant power equal to 32.4 W is described. Soil samples from the upper horizons of three types of loamy soils (Retisol, Phaeozem, Chernozem) were used in the experiment. For this purpose, a horn-type ultrasonic disruptor Digital Sonifier S-250D (Branson Ultrasonics, USA) with a stepped solid horn tip (13 mm) was used. It was found that the value of the total energy of dispersion Et required for complete destruction of soil aggregates to ESP depends on soil type and varies within 200–800 J·mL-1 for loamy soils with an organic matter content of 1.8–4.6 g. 100 g-1 soil. For sample preparation of soils for grain-size analysis with a subsequent determination of soil texture class according to Kachinsky classification, the value Et = 250 J·mL-1 is sufficient, as it allows obtaining the maximum amount of physical clay (<10 µm) at the minimum duration of sample preparation.