Srđan Šeremešić

The sensitivity of water extractable soil organic carbon fractions to land use in three soil types

ABSTRACT Soil organic carbon (SOC) has a high impact on the sustainability of ecosystems, global environmental processes, soil quality and agriculture. Long-term tillage usually leads to SOC depletion. The purpose of this study was to determine the impact of different land uses on water extractable organic carbon (WEOC) fractions and to evaluate the interaction between the WEOC fractions and other soil properties. Using an extraction procedure at 20°C and 80°C, two fractions were obtained: a cold water extractable organic carbon (CWEOC) and a hot water extractable organic carbon (HWEOC). The results suggest that there is a significant impact from different land uses on WEOC. A lower relative contribution of WEOC in SOC and a lower concentration of labile WEOC fractions are contained in arable soil compared to forestlands. Chernozem soil was characterized by a lower relative contribution of WEOC to the SOC and thus higher SOC stability in contrast to Solonetz and Vertisol soils. Both CWEOC and HWEOC are highly associated with SOC in the silt and clay fraction (<53 µm) and were slightly associated with SOC in the macroaggregate classes. The WEOC fractions were highly and positively correlated with the SOC and mean weight diameter.

Distribution of natural and artificial radionuclides in chernozem soil/crop system from stationary experiments

The present paper focuses on the determination of radiological characteristics of cultivated chernozem soil and crops from long-term field experiments, taking into account the importance of distribution and transfer of radionuclides in the soil-plant system, especially in agricultural cropland. The investigation was performed on the experimental fields where maize, winter wheat, and rapeseed were cultivated. Analysis of radioactivity included determination of the gross alpha and beta activity as a screening method, as well as the activities of the following radionuclides: natural (210Pb, 235U, 238U, 226Ra, 232Th, 40K, 7Be) and artificial (90Sr and 137Cs). The activities of natural and artificial (137Cs) radionuclides were determined by gamma spectrometry, while the artificial radionuclide 90Sr was determined by a radiochemical analytical method. Based on the obtained results for the specific activity of 40K, 137Cs, and 90Sr, accumulation factors for these radionuclides were calculated in order to estimate transfer of radionuclides from soil to crops. The results of performed analyses showed that there is no increase of radioactivity that could endanger the food production through the grown crops.

Aggregate stability and sealing risk of solonetz under different land use regimes

Solonetz is a type of alkaline soil which covers about 3.75% of the Province of Vojvodina, Serbia. In order to investigate the potential implementation of efficient agricultural production on this soil, we investigated the stability of structural aggregates and sealing risk (crusting hazard) in the surface layer (0-20 cm) of solonetz exposed to different land use. Four classes of stable aggregates (8000-2000, 2000-250, 250-53 and <53 μm) were obtained and the risk of sealing was calculated. The results show relatively stable structure in the surface layer of the investigated solonetz soils, but also a high risk of sealing. Solonetz under native vegetation showed higher aggregate stability and lower risk of sealing compared to solonetz exposed to long term tillage. Such soils can be recommended for establishing protective forests or cultivation of shallow rooted plants under condition that appropriate chemical properties of the surface horizon are monitored and cultivation practices against risk of sealing are implemented. Also further interdisciplinary study of these alkaline soils is recommended bearing in mind its high prevalence and variability of their properties.