Transformations of typical soil profile and organic matter in western lithuania agroecosystems

Abstract

El horizon becomes completely destroyed and a sequence of Retisols layers in the upper profile part changes from Ah-E-ElBt to the Ahp-ElBt. Likewise, significant transformation patterns were observed in the total and organic carbon content of the agrogenically transformed Retisols: the values of both total and organic C decreased twice in comparison to corresponding forest soils. The same trend is characteristic for humus content and humic acids composition. However, a systematic application of farmyard manure and liming has a positive effect on organic carbon content in the Retisol due to the growing number of carboxylic and phenolic groups that contain humic acids. Soil is a multicomponent and multifunctional system, with definable operating limits and a characteristic spatial configuration. Thus, the major challenge within sustainable soil management is to preserve soil multifunctionality for other ecosystem services while optimizing agricultural yields. The aim of the work is to determine the changes of morphological and chemical properties in Western Lithuania agroecosystems Retisols caused by their agrogenic transformation. Several methods used to study above mentioned transformations: a) particle size distribution of the soil particles in the liquid dispersion was determined using the light-scattering technique, b) soil pH was determined in 1M KCl (soil-solution ratio 1:2.5) using potentiometric method, c) soil organic carbon (SOC) content was determined by the Tyurin method modified by Nikitin (1999) with spectrophotometric measure procedure, d) mobile humic substances were extracted using 0.1M NaOH solution and determined according Ponomariova and Plotnikova (1980), e) water extractable organic carbon (WEOC) was determined in water extract (soil–water ratio 1:5) and measured by IR-detection method after UV-catalysed persulphate oxidation. Our study revealed a clear evidence of soil profile morphological and chemical changes to a depth of 40-50 cm, however, the most distinct transformations take place in the upper 30 cm layer of agrogenically changed Retisols. Thus, here it needs to be highlighted: when Ah horizon is deepening (by ploughing) from 10-15 cm up to 25-30 cm thick the El horizon becomes disturbed and partially incorporated/mixed into Ah horizon; the features of Ahp horizon changes Ah horizon and AhEl horizon develops (caused by soil deep loosening) at a later. Afterwards, due to the long-term deep plough practice and soil erosion (where it takes place),