The ecological conditions of arable lands in Uimon Depression located on the slopes under the influence of water erosion are discussed in the article. The study revealed that changes in some soil properties appeared during the last 30 years. It was found that basis on the most fundamental feature that is aggregate-size distribution the physical clay content accurately decreased up to 10,07%. Basis only on this feature these lands are estimated as the first degree of degradation. Reducing of the mobile potassium average content in a percentage from the average volume up to 40% corresponds to the second degree of degradation. For the soil fertility indicators such as humus horizon and humus store also revealed the first degree of degradation. Additionally, the article presents more detailed scale for assessing the environmental conditions of arable land than it was made by V.V. Vinogradov (1993). The cartogram of the arable land ecological status on the example of ZAO «Terek» (limited company) Ust- Koksinsky district in the Altai Republic has been made based on the results of investigation. The characteristic of environmental violation levels is given. In general, all arable lands are characterized by the degradation on 22%, i.e. they are on the average level of moderate crisis (К₁) with a reduction of productivity on 20–30%. The modes of rational soil use were developed taking into account peculiarities of climate, soil and geomorphology conditions of the farm land located in the northern part of the plowed southern slope in Uimon Depression, as well as the levels of the ecological status of the soils.