Soils of Agricultural Terraces on Clay Shales in the Mid-Mountain Zone of the Eastern Caucasus

Chemical properties and biological activity of soils of agricultural terraces on clay shales in the mid-mountain zone of the eastern Caucasus are analyzed. The area of terraced plots in the southern part of Dagestan is about 264 km2. These soils are now under fallow and represent a significant reserve of highly fertile erosion-resistant soils, the cultivation of which, unlike soils on consolidated rocks, is possible with the help of modern technology. The influence of slope exposure, steepness, terrace size, and duration of the plowing period on the chemical properties and biological activity of soils has been studied. It is shown that the slope exposure is a key factor for background soils outside the terracing zone. For terraced areas, its impact is less pronounced. The formation of terraces caused changes in the thermal regime of soils, and the differences in the chemical and microbiological properties of soils on the slopes of the northern and southern exposures became less pronounced. The leveling effect of terracing is most noticeable on relatively gentle slopes (12°–18°), where the width of the terrace surface is the greatest. On steep slopes (>20°) with narrow terraces, the effect of slope exposure on the soil properties is preserved. At the same time, factors such as the period of soil functioning and the features of agricultural technology, exert no less significant impact on soil properties. The regularities of changes in soil characteristics within one terrace have been established. Soil near the terrace edge, where the profile thickness is the greatest, is most fertile. The values of biological and chemical indicators regularly decrease towards the inner margin of the terrace.