The influence of agriculture on the chemical composition of gray soils from central Moldova

As a result of agricultural use of forest gray soils as arable land, instead fallow horizon Ao and
partly horizons A1 and A2 are formed arable Ap horizon. Prolonged use of gray soils in
agriculture led to their degradation, manifested by decreasing of organic matter due to its
mechanical destruction of valuable agronomic structure in the soil tillage process. Gray forest
soils are characterized by a clear differentiation of total chemical composition in the genetic
horizons. The mineral part of typical gray soil is composed of silicates and sesquioxides. In the
composition of researched soils is predominate silica compounds (SiO2), which make up 70-
77%. In the arable gray soil the SiO2 content is higher by 3.56% in humiferous soil layer than
in virgin forest gray soil. The vertical distribution of SiO2 in the soil profile has an accumulative
characteristic in humiferous horizon and partial in the parental rock. Share of oxides of Mg, Ti,
S, P, K and Na constitute an insignificant part. According relatively content in the gray soils the
oxides are located: SiO2→ Al2O3→ Fe2O3→ K2O→ Na2O→ CaO→ MgO→ TiO2→ SO3→
MnO→ P2O5. Utilization of forest gray soil in agriculture led to changes in their chemical
composition in the upper humiferous horizon and intensification of eluvial process in them. To
improve fertility of arable gray soils is necessary to increase organic matter in arable layer, to
remediate structure and combat erosion process.