Dynamics of selected chemical and microbiological properties changes in soils after application of ultra-fine powdered calcium carbonate – incubation studies

Soil acidification is a serious problem on a global scale, about 30% of land surface is occupied by acidic soils (pH≤ 5.5). Recent research indicates, that more than 50% of arable soils in Poland have too low pH. Acid soils are characterised the ability to mobilize toxic metals and increased plant uptake as well as decreased microbial activity in the soil. Progressive acidification leads to degradation of soils and caused that they are marginal for agricultural production. Soil acidification is a naturally occurring process, but only when natural factors are supported by intensive human activity, especially by nitrogen fertilisers application, intensive degradation is observed. Traditionally method to increase soil pH is the application of lime materials e.g. calcite, burnt lime or dolomite. The liming efficiency depends on lime material type (primarily chemical form of calcium compounds), the neutralising value, lime application method, soil properties and the particle size distribution of lime. The aim of this research was to determine the rate of action and influence of ultra-fine powdered calcium carbonate on selected chemical and microbiological soil properties.

The incubation studies were conducted on the three soils (G1, G2 – silt loam and G3 – sandy loam). Soil samples were taken from the 0-20 cm layer. Soil properties were measured after 7, 14, 30, 60 and 120 days of incubation. The liming factor was ultra-fine powdered calcium carbonate with particle size distribution < 0.08 mm. The application dose was calculated for 0.5 soil hydrolytic acidity. In the soil samples pH_KCl, buffer capacity, microbial biomass carbon and dissolved organic carbon content were measured.

Application of lime caused an increase of pH value in all studied soils. The highest increase of the pH_KCl was noted between 0 to 7^th day of incubation. Afterward, the pH_KCl decreased slowly for the soil G1 and G2. However, in the soil G3 significantly decreased just after 7^th to 14^th day, and afterward, the pH_KCl decreased slowly to the end of the incubation period. As a result of liming long-term changes in soil buffer capacity were not noted. The studied soils were characterised by the higher buffer capacity in alkaline than in acidic range. The microbial biomass carbon content was varied during the incubation in all studied soils. The dissolved organic carbon content increased during the incubation, starting from the 7^th to the 120^th day of incubation for G2 and G3 soils and from 14^th to last day of incubation for G1 soil. Application of lime caused an increase of the dissolved organic carbon content in all studied soils. These studies show that application of ultra-fine powdered calcium carbonate is an effective and fast way to improve soil properties.