Soil bulk density (BD) is often used to assess soil properties related to soil structure and general soil quality, or to convert weight units to volume/area units. Because collecting undisturbed soil ...samples (cores) and directly measuring BD is laborious and time-consuming, data on BD are often lacking. Pedotransfer functions (PTFs) can be used to predict BD from more readily available (easily measured) properties. However, specific PTFs for specific range of soils should be developed. In this study, soil organic matter (SOM) and clay contents of 90 forest Pseudogleys horizons, distributed across 11 locations in continental Croatia, were used to develop a multiple linear regression equation that predicts BD. The results have shown that the increase in BD due to the unit increase in clay content is lower than the decrease in BD due to the unit decrease in SOM content. PTF performance was relatively high (R.sub.adj.sup.2=77.5%, RMSE=0.1 g*cm.sup.-3, MAE=0.08 g*cm.sup.-3), showing that missing data on soil BD of Croatian Pseudogleys (or other similar soils, formed on similar parent materials) can be estimated reasonably well by using it. However, care should be taken when dealing with arable soils, which have different properties, compared with the natural soils considered herein.
Soil organic matter (SOM) plays a key role in ecosystems. Reduction of its content due to land-use changes has a negative impact on the soil, but also on the wider environment. Accordingly, SOM ...content is routinely analyzed in the laboratory. As these are expensive and/or time-consuming, indirect ones are also tested. The aim of this study was to examine the possibility of predicting SOM content by linear regression using soil color as the predictor, at three locations in Zagreb (Croatia), with different soil types (eutric cambisol anthropogenic, humofluvisol, pseudogley) and different land uses (plough land, meadow, forest, respectively). At each location, 5 samples of the surface soil layer were taken. Soil color was determined using the Munsell system, and the hue was 2.5Y and 10YR in dry and moist soil, respectively. Laboratory analyzes showed that the soils are very acid to neutral silt loams. In line with the land-use, they differed significantly in SOM content and were poorly humic (plough land), moderately to highly humic (meadow), and highly humic (forest). Correlation between soil color dimensions and SOM content was significant only for the dry samples, between chroma and SOM and between value/chroma ratio and SOM. Regression analysis showed high coefficients of determination for these two relationships (R.sup.2 = 0.88 for chroma-SOM, R.sup.2 = 0.76 for value/chroma-SOM). The results suggest that visual soil color determination can be used to estimate SOM content, but only in dry soil. The model calibrated in this paper needs to be validated using samples of other (different) soils. Keywords: humus, Munsell color system, linear regression, pedotransfer function SAETAK Organska tvar tla (OTT) ima kljucnu ulogu u ekosustavima. Smanjenje njenog sadraja zbog promjena u nacinu koritenja zemljita negativno utjece na sama tla, ali i na iri okoli. U skladu s tim, sadraj OTT redovito se analizira u laboratoriju. Kako su te analize skupe ili dugotrajne, testiraju se i one neizravne. Cilj rada bio je ispitati mogucnost predvidanja sadraja OTT linearnom regresijom koristeci boju tla kao prediktor, i to na tri lokacije u Zagrebu (Hrvatska), gdje je na svakoj utvrden razliciti tip tla (eutricno smede antropogenizirano, humofluvisol, pseudoglej) i razliciti nacin koritenja (redom: oranica, livada, uma). Na svakoj lokaciji je uzeto po 5 uzoraka povrinskog sloja tla. Boja tla odredena je Munsellovim sustavom, pri cemu je komponenta hue iznosila 2,5Y u suhom i 10YR u mokrom tlu. U laboratoriju je utvrdeno da su tla vrlo kisele do neutralne prakaste ilovace. U skladu s nacinom koritenja zemljita, signifikantno su se razlikovala u sadraju OTT te su bila slabo humozna (oranica), dosta do jako humozna (livada) i jako humozna (uma). Korelacija izmedu komponenti boje tla i sadraja OTT je utvrdena samo za uzorke u suhom stanju, i to izmedu komponente chroma i OTT te izmedu omjera komponenti value/chroma i OTT. Regresijom su utvrdeni visoki koeficijenti determinacje za navedena dva odnosa (R.sup.2=0,88 za chroma-OTT, R.sup.2=0,76 za value/chroma-OTT). Dobiveni rezultati sugeriraju da se vizualna metoda odred!vanja boje tla moe koristiti za procjenu sadraja OTT, ali iskljucivo u suhom tlu. Model kalibriran u ovom radu potrebno je validirati na uzorcima drugih (razlicitih) tala. Kljucne rijeci: humus, Munsell sustav boja, linearna regresija, pedotransfer funkcija DETAILED ABSTRACT IN ENGLISH Soil organic matter (SOM) plays a key role in ecosystems, especially in agroecosystems. Sensu stricto, SOM comprises the transformed (humified) organic residues which are often labeled as humus. Reduction of its content due to land-use changes has a negative impact on the soil, but also on the wider environment. Accordingly, SOM content is routinely analyzed in the laboratory. As these analyzes are expensive and/or time-consuming, indirect ones are also being tested. Some of the indirect methods include modelling of the SOM content based on the data for other (correlated and easily available) soil properties, such as soil color. Soil color is routinely determined during most soil surveys, requiring not much effort and resources. The aim of this study was to examine the possibility of predicting SOM content by linear regression using soil color as the predictor, at three locations in Zagreb (Croatia), with different soil types (eutric cambisol anthropogenic, humofluvisol, pseudogley) and different land uses (plough land, meadow, forest, respectively). All soils are found on flat terrain, at around 130 m above sea level. The climate of the studied area is humid, moderate continental. At each location, 5 samples of the surface soil layer were taken. Soil color was visually determined using the three dimensions of the Munsell system: hue, value, and chroma. Hue was 2,5Y and 10YR in dry and moist soil, respectively (with the moist soil samples having lower values). Chroma varied across the samples. The color was analyzed in soil peds under standardized conditions (light, moisture). Laboratory analyzes (soil pH, soil particle size distribution by pipette-method, SOM content by wet digestion after the Tjurin method) showed that the soils are very acid to neutral silt loams. In line with the land-use, they significantly differed in SOM content and were poorly humic (plough land), moderately to highly humic (meadow), and highly humic (forest). Statistical analyzes were performed using MS Excel and Minitab 19, and involved ANOVA, Kruskal-Wallis test, Pearson correlation, and linear regression procedures. The correlation between soil color dimensions and SOM content was significant only for the dry soil samples, between chroma and SOM and between value/chroma ratio and SOM. Regression analysis showed high coefficients of determination for these two relationships (R.sup.2 = 0,88 for chroma-SOM, R.sup.2 = 0,76 for value/chroma-SOM), with the following prediction errors: RMSE=1,08% and MAE=0,83% (chroma-SOM); RMSE=1,34% and MAE=1,10% (value/chroma-SOM). The obtained results suggest visual soil color determination can be used to estimate SOM content, but only in dry soils. However, the model calibrated in this paper needs to be validated on samples from other (different) soils. Moreover, further research should be conducted using a large number of samples, collected from soils across Croatia and the wider region.
Echinochloa crus-galli (L.) P. Beauv. is the most common monocotyledonous weed in maize crops in Croatia. Crop–weed interference is influenced by weed emergence patterns, and knowledge of the timing ...of weed emergence is crucial for the development of an efficient integrated weed-management program. Therefore, two-year field experiments were conducted in a maize crop sown in early May in continental Croatia to determine the emergence pattern of E. crus-galli from natural seedbank. In laboratory studies, the estimated base temperature and base water potential for the Croatian ecotype of E. crus-galli were 10.8 °C and −0.97 MPa, respectively. Then, the estimated germination parameters were compared with the values embedded in the AlertInf model from Italy (Veneto) to calibrate this hydrothermal model. The estimated hydrothermal units were around 28 for the onset (10%) and 93 for the middle (50%) emergence of E. crus-galli. Our findings showed that the AlertInf model satisfactorily simulated the emergence of E. crus-galli in maize crop in Croatia (EF = 0.97 in 2019 and 0.98 in 2020), indicating its potential use in other geographical areas
Erosion has been reported as one of the top degradation processes that negatively affect agricultural soils. The study objective was to identify hydropedological factors controlling soil water ...dynamics in erosion-affected hillslope vineyard soils. The hydropedological study was conducted at identically-managed Jastrebarsko (location I), and Jazbina (II) and (III) sites with Stagnosol soils. Soil Hydraulic Properties (SHP) were estimated on intact soil cores using Evaporation and WP4C methods; soil hydraulic functions were fitted using HYPROP-FIT software. For Apg and Bg/Btg horizons, uni- and bimodal soil hydraulic models could be well fitted to data; although, the bimodal model performed better in particular cases where data indicated non-uniform pore size distribution. With these SHP estimations, a one-year (2020) water flow scenario was simulated using HYDRUS-1D to compare water balance results obtained with uni- and bimodal hydraulic functions. Simulation results revealed relatively similar flux distribution at each hillslope position between the water balance components infiltration, surface runoff, and drainage. However, at the bottom profile at Jastrebarsko, bimodality of the hydraulic functions led to increased drainage. Soil water storage was reduced, and the vertical movement increased due to modified soil water retention curve shapes. Adequate parameterization of SHP is required to capture the hydropedological response of heterogenous erosion-affected soil systems.
Manganese (Mn) is an essential element that intervenes in several plant metabolic processes. The olive tree, and its fruits and leaves, are known as a source of nutraceuticals since they are rich in ...biophenols. However, there is still a serious lack of data about biophenolic distribution in olive stems and roots under Mn fertilisation. In this context, our study aimed to examine the effects of Mn fertilisation on the biophenolic profile in the leaves, stems, and roots of the ‘Istarska bjelica’ olive cultivar. The experiment was set up in a greenhouse, during a period of five months, as a random block design consisting of three treatments with varying Mn concentrations in full-strength Hoagland’s nutrient solution (0.2 µM Mn, 12 µM Mn, and 24 µM Mn). The obtained results indicate that the amount of Mn in the examined olive plant tissues was significantly higher under 12 µM Mn and 24 µM Mn treatments compared to that of the 0.2 µM Mn treatment. While the concentration of biophenols varied in roots depending on the compound in question, a strong positive impact of the increased Mn concentration in nutrient solution (12 µM Mn and 24 µM Mn) on the concentrations of the main biophenolic compounds was observed in stems. The concentration of oleuropein in leaves almost doubled at 24 µM Mn, with the highest Mn concentration, as compared to the 0.2 µM Mn treatment. The obtained results led to the conclusion that the supply of Mn could enhance the concentration of some biologically active compounds in olives grown hydroponically, implying a critical need for further investigation of Mn fertilisation practices in the conventional olive farming system.
Nitrate leaching through soil layers to groundwater may cause significant degradation of natural resources. The aims of this study were: (i) to estimate soil hydraulic properties (SHPs) of the ...similar soil type with same management on various locations; (ii) to determine annual water dynamics; and (iii) to estimate the impact of subsoil horizon properties on nitrate leaching. The final goal was to compare the influence of different SHPs and layering on water dynamics and nitrate leaching. The study was conducted in central Croatia (Zagreb), at four locations on Calcaric Phaeozem, Calcaric Regosol, and Calcaric Fluvic Phaeozem soil types. Soil hydraulic parameters were estimated using the HYPROP system and HYPROP-FIT software. Water dynamics and nitrate leaching were evaluated using HYDRUS 2D/3D during a period of 365 days. The amount of water in the soil under saturated conditions varied from 0.422 to 0.535 cm3 cm−3 while the hydraulic conductivity varied from 3 cm day−1 to 990.9 cm day−1. Even though all locations have the same land use and climatic conditions with similar physical properties, hydraulic parameters varied substantially. The amount and velocity of transported nitrate (HYDRUS 2D/3D) were affected by reduced hydraulic conductivity of the subsoil as nitrates are primarily transported via advective flux. Despite the large differences in SHPs of the topsoil layers, the deeper soil layers, having similar SHPs, imposed a buffering effect preventing faster nitrate downward transport. This contributed to a very similar distribution of nitrates through the soil profile at the end of simulation period. This case study indicated the importance of carefully selecting relevant parameters in multilayered soil systems when evaluating groundwater pollution risk.
•Model for coherent provenance analysis of soils based on heavy mineral assamblages.•Weathering pattern of heavy minerals suggests the parent material of terra rossa.•Recurrent supply of ...siliciclastic material from emerged shelf is crucial for terra rossa formation.
Coherent provenance studies of soils that take into account data processing and the limitations arising from the physiochemical properties of the source material are scarce. In this study, the provenance of four terra rossa soils on the Istrian peninsula and four terra rossa soils on the island of Susak is investigated based on the heavy mineral assemblages of the soils and their potential sources. The heavy mineral data are treated as compositional data, which means that the information is stored in the ratio between the components and not in absolute values. The provenance of the allochthonous soil components showed that they originated from the now submerged alluvial plain i.e., emerged Adriatic shelf, mainly fed by alpine material during low sea levels. In the case of Savudrija loess and red paleosol and partly Koreniki sections, the allochthonous material originated from the local Eocene flysch, also windblown from the emerged shelf. The degree of mineral weathering, which correlates with the Fed/Fet and the total portion of heavy minerals, shows that this allochthonous component is a parent material of the terra rossa soils, not an impurity. Thus, the main role of the carbonate rocks with which the terra rossa soils are associated is to maintain a specific and favorable conditions for their formation. The origin of the parent material is associated with sea level oscillations, i.e., in times of low sea level the material was windblown from the emerged shelf, onto the land, this recurrent process can probably be traced back to the Oligocene. During periods of high sea level, i.e., warmer periods, terra rossa formed. Thus, the formation of terra rossa soils in the northern Adriatic is a recurrent process that may have begun at least since the Miocene. Consequently, abundance of terra rossa on the eastern Adriatic coast is due to a large emerged shelf area that supplied the carbonate platform with siliciclastic material during low sea levels.
The B horizons of terra rossa soils developed on three different carbonate lithologies having variable insoluble residue contents were studied in Western Herzegovina. Comparison of their composition ...and properties illustrates to what extent the mineral, (especially clay mineral assemblage) and particle size distribution of those horizons and the insoluble residue of the underlying carbonate rocks can be used as indicators of the polygenetic nature of terra rossa in this region. Terra rossa B horizons have characteristic red colours, neutral to slightly acid pH, high base saturation with calcium as the predominant cation and high Chemical Index of Alteration (CIA). The CIA values obtained are generally in accordance with mineral composition and particle size distribution of the analysed B horizons. The predominant clay mineral phases in B horizons and related insoluble residues match. Kaolinite is the predominant clay mineral phase in the B horizons overlying carbonate rocks containing low amounts of insoluble residue, while smectite predominates in calcarenites areas with a high insoluble residue content.
Weathering indices are widely used in soil science and some other environmental disciplines for a variety of purposes (e. g. for soil classification, in soil formation studies, or in wider ...palaeoclimatic research). Two main categories of weathering indices have been developed: geochemical and mineralogical. In both cases, an approach is developed that takes into account the compositional nature of the geochemical data. To date, however, the most commonly used weathering indices are geochemical indices that do not consider the geochemical data as compositional. Although the compositional approach minimises possible statistical errors, the weathering indices developed in both approaches, i.e., compositional and classical, axiomatically assume two things that are inaccurate in some cases. First, that soil composition is invariant with respect to the preferential translocation of clay-sized particles, i.e. lessivage, and second, that the selective sorting of minerals during transport does not affect the values of weathering indices. As a result, in some cases bulk analyses of mineralogical and geochemical content are an unreliable tool for determining weathering rates of soil. To overcome these difficulties, this study proposes a new weathering index (Wp-min) based on the orthonormal log ratio (olr) transformation of quantitative mineral data derived from silt- to sand-sized allochthonous mineral assemblages. The size fraction used ensures that only the parent mineral assemblages, which are not prone to translocation, are analysed. In this paper, olr transformation is done using the concept of balances. This enabled the construction of variables, which essentially are various mineral log ratios, with the desired properties, i.e. transport invariance and sensitivity to selective dissolution. In this way, undesirable effects, i.e. selective sorting and lessivage, which ultimately affect bulk analyses, are avoided, allowing a more accurate estimation of weathering in the soil profiles studied. The new index was validated by comparison with the geochemical W index, which was modified by consulting the standardized variation matrix prior to element selection. Ultimately, compared to the geochemical index, the new index was better able to characterise weathering in soils where intense lessivage was detected. The study was conducted on terra rossa soils, which have common source, mostly of aeolian origin.
•The process of lessivage compromises conclusions about weathering•Modification of an existing geochemical index•Weathering rate derived from silt-sand sized fraction of parent minerals•Construction of a new weathering index
Loess-derived sediments represent the most widespread soil parent materials in the Pannonian region of Croatia. Pseudogley, as the most common soil type in this region, developed mainly on such ...parent materials. Pseudogleys largely correlate with the WRB Reference Soil Group of Stagnosols. On the General Soil Map of Croatia at scale 1: 50 000 (GSM of Croatia), the distinction is made between Pleistocene loams (PL) and loess as Pseudogley parent materials. The initial purpose of this research was to investigate if the criteria for this distinction were clear and consistent and if the terms used for labeling these parent materials were adequate. Hence, we investigated parent materials of 18 Pseudogleys across 6 different locations (three on loess and three on PL) in the Pannonian region of Croatia. We analyzed their morphology (including micromorphology of three representative parent materials), particle size distribution, total porosity, pH, and mineral assemblages (by modal analysis of three representative parent materials). Following these analyses, no systematic differences between the loess parent materials and the PL parent materials were found. Additionally, it was concluded that, due to significant geogenetic and/or pedogenetic alterations of all studied parent materials, none of them should be labeled simply as loess. Hence, parent material at one location was labeled as leached loess derivate, and parent materials at all other locations were labeled as pseudogleyed loess derivates. Both types of parent materials were described in detail and defined. In addition, the terminology and the classification of loess(-derived) parent materials in general was proposed. The analyzed pseudogleyed loess derivates were not completely uniform across the investigated locations. Primarily, this was due to the polygenesis of loess (reflected by differences in particle size distributions and compositions of light and heavy mineral fractions). Secondarily, it was due to the 600–1100 mm MAP gradient along the study region (reflected by differences in pH values and properties of redoximorphic features). Although pedogenesis of the investigated parent materials might have started already during the Late Glacial and have continued throughout the Holocene at varying (and overall decreasing) rates, their morphology indicates that pseudogleization and lessivage are still active processes, which occur simultaneously in the analyzed parent materials and agree with the present climate.
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