The effect of drip irrigation on the origin and size fraction of soil organic carbon was studied in the soils of an apple orchard (Malus domestica Borkh.) on hilly (20%) terrain in northeastern Slovenia in three slope positions (upslope, midslope and downslope), comparing irrigated with non-irrigated soils. Physical fractionation of soil organic carbon was performed on three soil layers (0-0.05, 0.05-0.15 and 0.15-0.30 m) in three size fractions: fraction A (> 0.0002 m), fraction B (0.0002-0.00005 m) and fraction C (< 0.00005 m). Fraction A was the richest in soil organic carbon (7.7%), but fraction C was the dominant fraction in the total soil volume (86-92%), making it the largest source of soil organic carbon (73%). The delta 13C signature was performed to determine the existence of two different types (origins) of soil orga-nic carbon: fresh and sedimentary. Fresh organic carbon dominates in the A fraction, while sedimentary organic carbon dominates in the C fraction and may contribute to higher structural stability, besides higher carbonates in the finest frac-tion. Irrigation mainly contributes to the higher stock of soil organic carbon (predominantly fresh and less sedimentary) in the coarse A fraction (21.14 t/ha in irrigated and 14.17 t/ha in non-irrigated soils).

This study sets out to examine the effects of hedgerow shading on soil physical properties, specifically soil gravimetric water content and soil temperature. Analyses of both soil parameters were conducted at two locations with different shade proportion. The aim of the study was to address the links between hedgerow shading and basic physical soil properties which could be significant both for agricultural production and for ecological processes in agroecosystems. At both locations, soil samples and measurements were taken at different distances from hedgerow and in different time intervals. Diurnal shading variation at certain distances from the hedgerow on Location 1 and 2 was calculated with the software toll for Arboriculturists. At Location 1 shading is consistently high throughout the year, ranging from 76 to 100%. In contrast, shading at Location 2 varies from 1 to 25%. The results reveal that hedgerows at Location 1, do not have a statistically significant impact on gravimetric soil water content and soil temperature across the entire plot surface. Additionally, the percentage of shading is only marginally decreases with distance. Conversely, Location 2 exhibits an increase in soil temperature and a slight but (non-significant) decrease in soil gravimetric watercontent as the distance from the hedgerow increases., The total mean shading at Location 2 is considerably lower compared to Location 1, and the shading percentage declines more at the distance from the hedgerow increases. Overall, lower soil temperatures and higher gravimetric soil water content where observed at the more shaded Location 1. The research outcomes are helpful in agricultural production planning as well as in the evaluation of hedgerows for the needs of agricultural policy.

The impact of drip irrigation on structural stability of soil aggregates was studied in soils of an apple (Malus domestica Borkh.) orchard, developed on marl. The field study was carried out in a sloping (20%) terrain in the northeastern Slovenia at three slope positions (upslope, mid-slope and downslope), involving a comparison of irrigated versus non-irrigated situations after 6 years of drip irrigation practice. Structural stability was studied in three soil layers (0-5, 5-15 and 15-30 cm) at the end of the irrigation season (in September). In the same samples, soil organic carbon, total carbonates and soil moisture contents were determined. Drip irrigation significantly reduced structural stability and soil organic carbon in the surface soil layer (0-5 cm), while total carbonates increased. Based on the whole set of data, structural stability was strongly positively correlated with total carbonates and negatively correlated with soil organic carbon. This means that the effect of higher level of organic matter mineralisation on structural stability, due to irrigation, is counterbalanced by the increase of total carbonates content in the fine textured calcareous soils. Thus, a negative effect of irrigation on soil organic carbon had less destructive consequences on structural stability than expected.

The presented study focuses on the use of thermogravimetric analysis (TG) for estimating organic (OC) and inorganic carbon (IC) contents in bulk soils of different soil types and agricultural practices. Total carbon (TC) was measured by dry combustion using a total organic carbon (TOC) analyzer. The OC content was obtained as the difference between the TC and IC measurements. Regression equations were developed for relations between the thermal mass losses over various temperature intervals (200–370, 105–550, 110–420, 180–450, 250–440, 250–650, and 200–575 °C) and the OC content to determine the optimal temperature interval for the estimation of OC. The results for IC contents were related to the thermal mass losses at temperatures ranging from 500 to 800 °C. The results demonstrated that the thermal mass losses between 180 and 450 °C were fairly well related to the OC content (R 2 = 0.63), whereas the root-mean-square error of cross-validation (RMSECV) was too high (0.70 % OC). The inclusion of the clay content in the multivariate predictive equation did not importantly lower the RMSECV. By contrast, the thermal mass losses within the interval from 500 to 800 °C were closely related to the IC content determined using the TOC analyzer (R 2 = 0.96), with an acceptable RMSECV of 0.26 %. These results indicate that TG can provide a reliable estimation of the IC content but only rough estimations of the OC content in bulk soils of different types, bedrocks, and land uses.