Evaluating Soil Particle Analysis Methods for Tropical Andosols in Indonesia

Abstrak

Choosing the right method to quantify soil particles (sand, silt, clay) is essential to predict and manage
soil characteristics in relation to e.g. nutrient or water retention. However, separating silt and clay
particles for volcanic soils is difficult. In this study, we investigated the effect of three different soil
particle analysis methods, namely the regular pipette method, Na-resin dispersion, and
ultrasonication with high energy level (1500 J ml
-1
) on the distribution of soil particle size in tropical
volcanic soils. Ultrasonication with high energy level was founded to be the best method to fully
separate silt and clay fraction compared to Na-resin and regular pipette method. In conversion, the
dispersion of soil particles using regular pipette method was suboptimal. In the ultrasonication
method, a step that is important to achieve full dispersion is pH buffer > 8 in soil suspension. This
ultrasonication method was founded to have good correlation with Na-resin dispersion method (R =
0.88). This study suggested that conventional particle size analysis may not fully separate sand, silt,
and clay particles correctly in soils rich in amorphous materials and oxides, and we proposed
ultrasonication high energy level with pH buffer > 8 method as an alternative method.