The content and composition of humus of chestnut saline soils of various agricultural uses in the conditions of the dry steppe of the Western Manych valley

The results of a study on the comparative characteristics of the content and composition of humus of virgin and chestnut saline soils of various agricultural uses in the conditions of the dry steppe of the Western Manych valley are presented. It was revealed that, under anthropogenic influence, humus decreases to 2.15% in the upper layer and 1.8% down the profile in chestnut saline soils, and humus reserves are 85 t/ha and 72 t/ha, respectively. In an area with a high degree of pasture load, humus and its reserves are lost by an average of 1.5 times relative to the virgin area. A change in the qualitative composition of humus from the humate-fulvate type in the upper horizons to the fulvate type down the profile was found, while a decrease in the fractions of humic and fulvic acids associated with exchangeable calcium and an increase in stable humus fractions were noted. The assessment of humus status indicators showed a decrease in the fertility of chestnut saline soils under agricultural use to a low level.