Physic-Chemical Characteristics of Organo-Clay Complexes of Agrochernozems of Different Localization on the Slope

Abstract

Organo-clay complexes of agrochernozems of different localization on the slope were studied, including by the method of dynamic light scattering (DLS). A decrease in the concentration of organic carbon (Corg) of silty fractions in the arable horizons of washed-out agrochernozems was revealed, which was a consequence of the constant exposure of the soil mass of the underlying horizon, provoking the decomposition of organic matter(s). This was accompanied by changes in the content of non-silicate iron (Fed) as a result of oxidative degradation of organo-iron complexes, which contributed to the desorption of Fed. Different intensity of erosion processes influenced the tendency to change the dynamics of Fed: a lower slope steepness (4°) contributed to an increase in the load of Corg on iron oxides, resulting in an increase in iron desorption, whereas in conditions of greater steepness (6°), a decrease in iron desorption was observed. Regardless of the position on the slope, the highest values of the average diameter of organo-clay complexes (D) were observed in the upper horizons of the studied agrochernozems, which decreased down the profile. As a result of erosion processes, the size of organo-clay complexes in arable horizons decreased in comparison with that in non-eroded agrochernozems (by 1.1 times). It was revealed that the size of organo-clay complexes in the studied agrochernozems was determined by the values of the content of Corg and Fed, although the degree of their significance differed in the upper humus (Aarable, A1, AB) and lower (B, C) horizons. In the upper horizons, the value of D was determined by the content of Corg, whereas in the lower horizons, the main role in the formation of the size of organo-clay complexes belonged to Fed. The obtained data allowed us to assume a more significant role of organic matter (OM) in the aggregation of cley particles compared to that of Fed. The hypothesis of a multiple linear regression dependence of the value of D on the values of the concentration of carbon (Corg and Ccarbonates) and Fed in them turned out to be statistically significant both for the entire set of genetic horizons and for humus horizons The coefficient of determination of the model (R2) increased in a row: 0.578 (Apl + A1) 0.678 (Apl + A1 + AB + B + BC + C) 0.724 (Apl + A1 + AB) 0.983 (AB).