Features of the structural-aggregate composition of ordinary chernozems under the steppe and forest vegetation

Abstract

The structural-aggregate composition is an important soil characteristic, which reflects the features of the genesis, condition and regimes of soils. The structural and aggregate composition of ordinary chernozems under zonal steppe vegetation and under artificial forest plantations from white acacia and common oak in the conditions of the Prisamaría was studied. As a result, it was found that in all the studied soils the greatest content falls on the fraction 2–1 mm in size. In ordinary chernozems in the upper horizons, under the stands of white acacia and common oak, an increase in the content of this agronomically valuable fraction is observed. Also in ordinary chernozem under forest stands, an increase in the value of the structural coefficient is observed compared with ordinary chernozem under steppe vegetation. In ordinary chernozem the most favorable effect of the growth of white acacia was found in horizon H, and the growth of ordinary oak in horizon H2, in which the highest values ​​of the structural coefficient were found. In the studied ordinary chernozems under the steppe and forest vegetation a predominance of the water-resistant fraction of size <0.25 mm is observed. The positive effect of white acacia and common oak plantations on the water resistance of aggregates of common chernozem in the upper horizons is manifested in a decrease in the content of the fraction of size <0.25 mm compared to ordinary chernozem. In ordinary chernozems under steppe vegetation the most favorable conditions for the formation of agronomically valuable fractions during dry sieving are characteristic of the lower horizons and for chernozems under forest stands in the upper horizons. In all the studied soils the highest content of agronomically valuable fractions during wet sieving was found in the upper horizons, but there are more of them in chernozems under forest stands. The highest content of agronomically valuable fractions in all studied soils is observed in the lower horizons and their highest content in the upper horizons is found in ordinary chernozems under the steppe vegetation. The highest values ​​of the water resistance criterion are characteristic of the lower horizons of the studied chernozems. The maximum values ​​of this criterion were found in ordinary chernozem under oak plantation, and the smallest – under acacia plantation. The growth of forest plantations on ordinary chernozems leads to an improvement in their structural-aggregate composition.