The mechanical expresion provides for the use of Soil property reserves and permanent protec-tion or improvement of soil resources in accordance with measurable standards. If the functions J (initial soil property), E (soil erosion), R (soil renewal), and M. (minimum al-lowable value) are assumed to be integrable in region A, erosion tolerance over a region is leaded to ∫a ∫I(m cl, re, ch, b)dA-∫A ∫ { $∫infty$∫ to [E(w r, cl, re, ch, b, t) -R(m, ch, re, b, t)]dt} dA>= ∫A∫ Mi(m cl, re, ch, b)dA were variable factors are m=parent material of soil, cl=climate, re=relief or topography, ch=soil characteristics, r=rain or water, w=wind, b=biota, and t=time. Key words: Theoretical analyses, Soil erosion, Conservation, Erosion tolerance