An acid-base buffering model to describe pH buffering capacity of an acid albic stagnic luvisol under long-term agricultural land use and management

Aim. To study acid-base buffering capacity depending on the intensity of different fertilization systems, including lim- ing, with different doses of CaCO3 in a long-term (55 years) stationary experiment on Albic Stagnic Luvisol (light grey forest surface-gleyed soil). This study should serve as a basis for the restoration and protection of fertility and yield and preservation of ecological restorative functions of this soil type. Methods. Field stationary experiment, using monitoring, laboratory-analytical and statistical-mathematical methods. Results. It was found that after 35 years of a seven-field crop rotation the exclusion of the intensive crops of sugar beet, potato and one winter wheat, in combina- tion with low (2.5 time less) mineral fertilization levels, contributed to an increase in resistance to acidification over the next 20 years from 5.53 to 7.48 points (using a 100-point scale) with a simultaneous increase in soil рНКСl from 3.77 to 4.12. Organo-mineral fertilization (N65P68K68 + 10 t manure/ha of crop rotation area) and periodic application of CaCO3 by hydrolytic acidity (6.0 t/ha) and an optimal dose of lime (2.5 t/ha CaCO3) increased pH buffering over these 20 years in a four-field rotation. The general evaluation index of buffering was 21.8–21.9 points, exceeding the virgin soil by 1.9 to 2 points. In the control variants without the use of fertilizers the general evaluation index of buffering was 14.3 ± 0.3, and the coefficient of buffer asymmetry was the highest – 0.646 ± 0.013, which under these conditions indicated the danger of soil losing its ability for self-regulation and self-healing. Conclusions. The resis- tance of Albic Stagnic Luvisol to acidification increased most in the combined application of N65P68K68 and 10 t/ha manure, together with an optimum calculated dose of lime in a 4-year crop rotation. An optimal dose of CaCO3 (2.5 t/ha) and organo-mineral fertilizing system in a 4-year crop rotation improved the soil buffering capacity of the acid shoulder by 2.45 points compared to the mineral fertilization system. To support a determination of acid-buffering effects graphic charts representing pH buffering capacity proved to be useful and could be instrumental in diagnostics and optimization of the acid-base regime for acid forest soils in general.