Which soil types make parts of Ukraine and southwestern Russia highly fertile?

The exceptional fertility of the soil in parts of Ukraine and southwestern Russia is primarily due to the presence of chernozems, also known as black earths.123

These soils are characterized by their deep, friable structure and high humus content, which is derived from the thick cover of grass that historically dominated the steppe regions. The formation of these fertile soils is aided by specific environmental conditions: winter frost and summer drought inhibit the rapid decomposition of organic matter, while high evaporation rates prevent the leaching of essential nutrients. Additionally, these soils benefit from low acidity and a lime-rich horizon that forms beneath the humus layer, creating an environment highly conducive to grain cultivation and other agricultural production.23