Ivana Šestak

Sulphur cycling between terrestrial agroecosystem and atmosphere

Central gas station of the natural gas borehole system Podravina is located near the village Molve. It delivers more than a quarter of total energy used in Croatia to its consumers. Over the years, adapting technology to increasingly demanding and rigorous standards in environmental protection has become paramount. Yet, despite all the industry has undertaken to address the risk of harmful substances entering the food chain, a multidisciplinary research team of independent scientists monitors the content of specifi c substances in all components of the ecosystem. This paper presents measurements of total sulphur contents in soil surface [(0 to 3) cm] and subsurface [(3 to 8) cm] layers (study period: autumn 2006 - spring 2010) and in plants (study period: spring 2000 - spring 2010), and the concentration of gaseous sulphur compounds in the air. Concentrations of hydrogen sulphide (H2S) and mercaptans (RSH) were measured from the summer of 2002 until the autumn of 2010, while concentrations of sulphur dioxide (SO2) were measured from the spring of 2008 until the autumn of 2010. The paper also shows total annual atmospheric sulphur (S-SO4) deposition at Bilogora measuring station (study period: 2001 - 2010). Average monthly concentrations of H2S in air varied between 0.2 μg m-3 and 2.0 μg m-3, RSH between 0.1 μg m-3 and 24.5 μg m-3, and SO2 between 0.4 μg m-3 and 2.8 μg m-3 depending on the location and the season of sampling. Mean values of total sulphur in soil and in Plantago lanceolata plant ranged between 610 mg kg-1 and 1,599 mg kg-1 and between 3,614 mg kg-1 and 4,342 mg kg-1, respectively, depending on the soil type, location, and sampling depth. Average values of total sulphur mass ratio for all examined single soil samples (n=80) were 1,080 mg kg-1 for both studied layers, and 4,108 mg kg-1 for all analysed plant samples (n=85). Average total annual atmospheric sulphur deposition at Bilogora measuring station was 6.3 kg of S-SO4 per hectar.

Radioactivity of Selected Agricultural Soils in Croatia: Effects of Soil Properties, Soil Management, and Geological Parameters

We present a study on the radioactivity of selected Croatian agricultural soils that vary considerably with respect to geological background; physical, chemical, and biological characteristics; soil type; land use; and soil management. Our investigation is focused on the main naturally occurring radionuclides (40K, 238U, 226Ra, 232Th, 235U) and 137Cs as the most threatening long-lived anthropogenic radionuclide. We find that the radioactivity level is not influenced by the application of different soil amendments, at least in moderate quantities, and that no effect of soil management can be detected as well. In contrast, geological and location-specific properties influence radionuclide content in soil, especially regarding the naturally occurring ones. Moreover, physical and chemical soil properties such as texture and soil adsorption complex, respectively, seem to be the main factors regarding fixation of 137Cs in soil. Calculated dose rates for external exposure to the gamma radiation originating from soil have been found to be generally low, except for two locations where they are higher but not at a level that would lead to health problems for workers on the field.

Soil Carbon Variability in Some Hungarian and Croatian Soils

Loss of soil carbon and carbon storage were studied in different soil types in the agroecological conditions of the Pannonian plain and in the Mediterranean region. Total carbon concentration, pH and C:N ratio under pastures, meadows, forests, vineyards, gardens and crop fields were determined. Soil samples were taken in 2010 at depths from 0–3, 3–10, 0–30, 30–60 and 60–90 cm depending on the location, region, soil type and type of ecosystem. Soil pH varied between strongly acid 4.3 measured in crop field on distric Stagnosols (0–30 cm) to weakly alkaline 7.6 in a crop field on Chernozems; C:N ratio varied from 8 measured on distric Stagnosols to 39 on Cambisol calcaric; Soil carbon concentration observed in this study varied from 3.3 g C/kg at Szentgal on an agricultural crop field on Eutric Cambisol, in the deep layer (60–90 cm; L4) to 107.2 g C/kg on Regosol on karst measured in the surface layer of a Mediterranean grassland (0–3 cm; L10).

Visible and near infrared reflectance spectroscopy for field-scale assessment of Stagnosols properties

Spectral data contain information on soil organic and mineral composition, which can be useful for soil quality monitoring. The objective of research was to evaluate hyperspectral visible and near infrared reflectance (VNIR) spectroscopy for field-scale prediction of soil properties and assessment of factors affecting soil spectra. Two hundred soil samples taken from the experiment field (soil depth: 30 cm ; sampling grid: 15 × 15 m) were scanned using portable spectroradiometer (350–1050 nm) to identify spectral differences of soil treated with ten different rates of mineral nitrogen (N) fertilizer (0–300 kg N/ha). Principal component analysis revealed distinction between higher- and lower-N level treatments conditioned by differences in soil pH, texture and soil organic matter (SOM) composition. Partial least square regression resulted in very strong correlation and low root mean square error (RMSE) between predicted and measured values for the calibration (C) and validation (V) dataset, respectively (SOM, %: RC2 = 0.75 and RV2 = 0.74 ; RMSEC = 0.334 and RMSEV = 0.346 ; soil pH: RC2 = 0.78 and RV2 = 0.62 ; RMSEC = 0.448 and RMSEV = 0.591). Results indicated that hyperspectral VNIR spectroscopy is an efficient method for measurement of soil functional attributes within precision farming framework.

Land use change and soil fertility assessment in the vicinity of Zagreb landfill

The aim of this study was to give quantification of the present land use, land use change and assessment of agricultural soil in the area surrounding Jakusevec landfill in Zagreb, Croatia. A map of land use types of approximately 2 km zone around the landfill was created, based on photointerpretation during 2012 and according to Corine Land Cover 2000, 2006 and 2012 database. For soil fertility evaluation, soil was sampled at four locations at a distance of up to 300 m around the landfill. Spatial analysis revealed thirteen land use categories of total size around 3,161 ha. These categories were divided into three larger groups based on land use types (water: 5%, agricultural land: 50% and city: 45% of the total analysed area). Mixed agriculture is very important in this urban area regardless of the closeness of the waste landfill, because it relies on fertile soil and vicinity of large market of the capital city. The main land use changes included increase in industrial or commercial units and transport infrastructure, and decrease of agricultural land.

Precise Soil Sampling Method for Agricultural and Environmental Research Based on New Circular Soil Probe Apparatus

Conventional soil sampling usually implemented in Croatia considers sample weight of 2 kg per 4-5 ha area, which means that representative sample in relation to soil mass up to 30 cm depth is presented through the ratio 1:10000000. New sampling method changes the ratio to 1:625000, thus increasing amount of sampled soil 16 times with assumption that such sample better describes investigated area. Moreover, new soil sampling probe can be used for precision farming purposes where the central point of the probe ring is positioned with precision of ±1 cm and represented with 4, 8 or 16 samples taken in 50 cm radius from the center. Soil probe prototype was tested on agricultural land of 4 ha area with total number of 200 samples. To justify application of new constructed probe, this study gives results of geostatistical analysis of spatial variability in soil pH values up to 30 cm depth. Ordinary kriging was used as interpolation method. Spatial structure of soil parameter was analyzed by calculating semivariograms and approximated by exponential model. Root-mean-square error (RMSE) of prediction was used as measure for the best model evaluation. Interpolation analysis of reduced number of samples per investigated area of 4 ha resulted in deviation in RMSE of 13,2 % when 50 % less samples were randomly introduced, and 41 % with 60 samples, compared to total of 200 samples. Using new soil sampling method for soil survey and applied geostatistical tools provides a solution for quantifying spatial variability of soil properties, possibilities for commercial activities and a way to introduce variable rate technology in agricultural input application which can optimize farm profitability through improving yield, reducing input costs and minimizing input losses to the environment.