Prostorno mapiranje kemijskih svojstava tla koristeći multivarijatnu geostatistiku. Studija s oraničnih tala u istočnoj Hrvatskoj

The spatial variability of soil chemical properties is affected by factors of soil formation and human activities. Understanding their spatial variability will improve agricultural production, reduce environmental problems (e.g., soil pollution, offsite effects), and achieve sustainable agroecosystems. The main objective was to study the spatial variability of pH, soil organic matter, available phosphorus, and available potassium using univariate and multivariate methods in cropland fields in eastern Croatia. For the study, 169 (0-30 cm) soil samples were collected in a 911 ha study area. The results showed that soils had slightly acidic pH, adequate available phosphorus and potassium values for crop production, and low soil organic matter concentration. The variability was high in available phosphorus and low in pH. Soil pH, soil organic matter, available phosphorus, and potassium nugget/sill ratio was 0.00, 2.79, 18.68, and 22.08, respectively. Auxiliary variables increased the accuracy of the predictions. Soil organic matter levels were below the recommendable, and this is very likely an anthropogenic effect, even though the intrinsic process influences soil organic matter. The heterogeneous distribution of phosphorus and potassium highlighted the necessity of fertilization in some areas. For the sustainability of agroecosystems, adaptable site-specific soil management strategies need to be implemented.Prostorna varijabilnost kemijskih svojstava tla uvjetovana je pedogenetskim čimbenicima i ljudskom aktivnošću. Razumijevanje prostorne varijabilnosti poboljšati će poljoprivrednu proizvodnju, smanjiti okolišne probleme (npr. zagađenje tla, off-site učinci), i postići održivost agroekosustava. Glavni cilj rada je istraživanje prostorne varijabilnosti pH, organske tvari i biljci pristupačnog fosfora i kalija, koristeći univarijatne i multivarijatne metode na oraničnim tlima u istočnoj Hrvatskoj. Za rad je prikupljeno 169 (0-30 cm) uzoraka tla s površine od 911 ha. Rezultati pokazuju da su tla blago kisela, adekvatnog sadržaja biljci pristupačnog fosfora i kalija za biljnu proizvodnju i niskog sadržaja organske tvari tla. Varijabilnost je visoka kod biljci pristupačnog fosfora i niska kod pH tla. pH tla, organska tvar te biljci pristupačan fosfor i kalij imaju nuget/sill omjer 0.00, 2.79, 18.68, i 22.08. Pomoćni podaci povećali su preciznost predikcije. Identificiran je sadržaj organske tvari tla ispod preporučljive razine i to vrlo vjerojatno radi antropogenog utjecaja, iako i pedogenetska svojstva utječu na organsku tvar tla. Heterogena distribucija fosfora i kalija istaknula je nužnost za gnojidbom u nekim područjima. Za održivost agroekosustava potrebno je provesti prilagodljive strategije korištenja i upravljanja tlima na svakoj pojedinoj lokaciji

Temperature rise and DC current capability tests of star-point reactor used in HVDC transmission

Star-point reactors are grounding devices installed in HVDC stations between the converter transformer secondary side and AC side of converter arms to provide a reference to ground. Such reactors are used as high-impedance grounding on the converter side of power transformers, providing high impedance path for the fundamental harmonic (i.e. 50 or 60 Hz) and a low impedance path for DC current, eliminating DC current flowing through the transformer windings. Temperature rise and DC current capability tests of 420 kV star-point reactor are presented in this paper. The purpose of temperature rise test is to verify that temperatures that can damage the insulation of star-point reactor will not be reached with the specified service conditions. The temperature rise test was carried out according to the requirements of the IEC 61869-3 standard and client’s request which included simultaneous application of fundamental, 3rd harmonic voltage and DC excitation. The inclusion of 3rd harmonic excitation of an amplitude up to 15% simulates voltage harmonic distortion which may appear in the power system at the location of star-point reactor installation. Prior to temperature rise test, DC current capability test was performed. The goal of this test is to determine the value of DC current at which the saturation point is reached. DC current is injected through star-point reactor while AC voltage is applied. Two different cases are considered regarding AC voltage: test with fundamental voltage harmonic and test with fundamental voltage harmonic with superimposed third voltage harmonic. Test circuit is proposed which is suitable for generation of complex voltages composed of fundamental harmonic and superimposed third harmonic with amplitudes up to 15% of the applied fundamental harmonic. The proposed test circuit was also used during the temperature rise test and it is applicable for testing of HV equipment with rated voltage up to 420 kV

MODELLING CONVECTIVE THIN-LAYER DRYING OF CARROT SLICES AND QUALITY PARAMETERS

The influence of thin layer convective dehydration parameters on drying kinetics parameters, chemical composition, and color parameters of carrot slices were investigated, and corresponding mathematical models were developed. In the carrot slices, convective dehydration process hot air temperature and the sample slice thickness were varied, while measured, calculated, and modeled responses were: time of dehydration, effective moisture diffusivity, the energy of activation, proteins and cellulose contents, lightness, redness, and yellowness. The obtained results showed that varied convective dehydration process parameters statistically significantly affected all investigated responses except activation energy. The most efficient drying model with the minimum thickness (3 mm) and the maximum drying temperature (70 °C) had the shortest drying time (231 minutes). This model had the minimum resistance to mass transfer (the minimum effective moisture diffusivity, 2.04. 10–08 – 7.12. 10–08 [m2s–1]), and the average maximum energy of activation (31.31 kJ/mol). As far as the carrot slices’ chemical composition and color parameters were concerned, the model with the maximum thickness (9 mm) and the minimum drying temperature (35 °C) was the optimal one. This model had the longest dehydration time (934 minutes), the maximum resistance to the mass transfer (8.87. 10–08 [m2s–1]), the minimum total protein content (5.26 %), and the darkest color (49.70). The highest protein content (7.91%) was found for the samples subjected to the highest drying temperatures and the lowest carrot slice thickness. In contrast, the process of convective dehydration had led to the lighter, reddish, and yellowish carrot slices. All developed mathematical models were statistically significan

Investigating near-surface hydrologic connectivity in a grass-covered inter-row area of a hillslope vineyard using field monitoring and numerical simulations

The interplay of surface and shallow subsurface fluxes plays a critical role in controlling water movement in hillslope agroecosystems and impacting soil and plant health during prolonged dry periods, demonstrating a need for in-field monitoring. This study was conducted for two years (2021–2022) by combining field monitoring of the grass-covered inter-row area (passive wick lysimeter, surface runoff, and meteorological data), laboratory determination of soil hydraulic properties (SHPs), and numerical modeling with the aim to explore near-surface fluxes at the SUPREHILL Critical Zone Observatory (CZO) located on a hillslope vineyard. Additionally, sensitivity analysis for basic root water uptake (RWU) parameters was conducted. The model was evaluated (R2, RMSE, and NSE) with lysimeter (hillslope) and runoff (footslope) data, producing good agreement, but only after the inverse optimization of laboratory estimated hydraulic conductivity was conducted, demonstrating that adequate parameterization is required to capture the hydropedological response of erosion-affected soil systems. Results exhibit the dependence of runoff generation on hydraulic conductivity, rainfall, and soil moisture conditions. The data suggest different soil-rewetting scenarios based on temporal rainfall variability. Sensitivity analysis demonstrated that Leaf Area Index (LAI) was the most responsive parameter determining the RWU. The study offers an approach for the investigation of fluxes in the topsoil for similar sites and/or crops (and covers), presenting the methodology of self-constructed soil–water collection instruments. © 2023 by the authors

Comparison of RISK-PCI, GRACE, TIMI risk scores for prediction of major adverse cardiac events in patients with acute coronary syndrome

Aim To compare the prognostic performance of three major risk scoring systems including global registry for acute coronary events (GRACE), thrombolysis in myocardial infarction (TIMI), and prediction of 30-day major adverse cardiovascular events after primary percutaneous coronary intervention (RISK-PCI). Methods This single-center retrospective study involved 200 patients with acute coronary syndrome (ACS) who underwent invasive diagnostic approach, ie, coronary angiography and myocardial revascularization if appropriate, in the period from January 2014 to July 2014. The GRACE, TIMI, and RISK-PCI risk scores were compared for their predictive ability. The primary endpoint was a composite 30-day major adverse cardiovascular event (MACE), which included death, urgent target-vessel revascularization (TVR), stroke, and non-fatal recurrent myocardial infarction (REMI). Results The c-statistics of the tested scores for 30-day MACE or area under the receiver operating characteristic curve (AUC) with confidence intervals (CI) were as follows: RISK-PCI (AUC = 0.94; 95% CI 1.790-4.353), the GRACE score on admission (AUC = 0.73; 95% CI 1.013-1.045), the GRACE score on discharge (AUC = 0.65; 95% CI 0.999-1.033). The RISK-PCI score was the only score that could predict TVR (AUC = 0.91; 95% CI 1.392-2.882). The RISK-PCI scoring system showed an excellent discriminative potential for 30- day death (AUC = 0.96; 95% CI 1.339-3.548) in comparison with the GRACE scores on admission (AUC = 0.88; 95% CI 1.018-1.072) and on discharge (AUC = 0.78; 95% CI 1.000- 1.058). Conclusions In comparison with the GRACE and TIMI scores, RISK-PCI score showed a non-inferior ability to predict 30-day MACE and death in ACS patients. Moreover, RISK-PCI was the only scoring system that could predict recurrent ischemia requiring TVR

Straw mulch effect on soil and water loss in different growth phases of maize sown on stagnosols in Croatia

Soil and water loss due to traditional intensive types of agricultural management is widespread and unsustainable in Croatian croplands. In order to mitigate the accelerated land degradation, we studied different cropland soil management strategies to obtain feasible and sustainable agro-technical practices. A rainfall simulation experiment was conducted at 58 mm h–1 over 30 min on 10 paired plots (0.785 m2), bare and straw covered (2 t h

Nutritional attributes of wheat bread fortified with convectively dried chokeberry powder

Chokeberry (Aronia melanocarpa L.) has a positive effect on human health, and therefore it can be used as a beneficial component for food (e.g. wheat bread) fortification. Dried chokeberry powder (CP), obtained by convective drying at 50, 60, and 70°C, fortified bread samples by replacing wheat flour at levels of 1, 2.5, 5 and 10%. Bread samples fortified with chokeberry were characterized by a decrease in total starch and protein contents and an increase in total sugar, mineral (Mg, Ca, Cu), and fat components; unsaturated oleic acid was reduced, unlike unsaturated linoleic and linolenic acids. All developed mathematical models for starch, protein, fat, and minerals in bread supplemented with CP were characterized by statistically insignificant residual variances and high values of R2. Z-score analysis showed the optimal segment and total scores of bread fortified with CP. Chokeberries dried at a temperature of 60°C showed the best nutritional attributes. Wheat bread enriched with CP in the amount of 10% had the highest level of fortification.Publishe

Modeling water flow and phosphorus sorption in a soil amended with sewage sludge and olive pomace as compost or biochar

Organic amendments are often reported to improve soil properties, promote plant growth, and improve crop yield. This study aimed to investigate the effects of the biochar and compost produced from sewage sludge and olive pomace on soil hydraulic properties, water flow, and P transport (i.e., sorption) using numerical modeling (HYDRUS-1D) applied to two soil types (Terra Rosa and Rendzina). Evaporation and leaching experiments on soil cores and repacked soil columns were performed to determine the soil water retention, hydraulic conductivity, P leaching potential, and P sorption capacity of these mixtures. In the majority of treatments, the soil water retention showed a small increase compared to the control soil. A reliable fit with the modified van Genuchten model was found, which was also confirmed by water flow modeling of leaching experiments (R2 0.99). The results showed a high P sorption in all the treatments (Kd 21.24 to 53.68 cm3 g−1), and a high model reliability when the inverse modeling procedure was used (R2 0.93–0.99). Overall, adding sewage sludge or olive pomace as compost or biochar improved the Terra Rosa and Rendzina water retention and did not increase the P mobility in these soils, proving to be a sustainable source of carbon and P-rich materials

UTJECAJ PONAVLJANJA PROHODA TRAKTORA NA NEKA FIZIKALNA SVOJSTVA PRAŠKASTO-ILOVASTOGA TLA

The aim of this paper was to quantify soil compaction induced by tractor traffic on untilled wet silty loam soil (Mollic Fluvisol). Changes in penetration resistance, bulk density and total porosity were measured for detecting the soil compaction. Treatments include ten passes of a four-wheel drive tractor with the engine power of 54.0 kW and weight of 3560 kg (1580 kg on the front axle and 1980 kg on the rear axle, 2.41 m distance between axles). The tyres on the tractor were cross-ply, front 11.2-24 and rear 16.9-30, with the inflation pressure of 160 kPa and 100 kPa, respectively. The speed of tractor during passes over experimental plots was 5.0 km h-1. In comparison to control, each tractor pass induced an increase in soil penetration resistance at all depths, and the average increment ratios, determined as the average of all layers, were 9.8, 18.5 and 26.1% after one, five and ten passes, respectively. The bulk density also increased with number of tractor passes, but with less percentage increasing. The increment ratios comparison to the control were 3.6, 9.5 and 12.9% after one, five and ten passes, respectively. The total porosity decreased with the number of passes, and the decrement ratios were 4.5, 16.5 and 20.8% after one, five and ten passes, respectively.Cilj ovoga rada bio je odrediti zbijanje tla prouzročeno kretanjem traktora po neobrađenome vlažnome praškastoilovastom tlu (Mollic Fluvisol). Za određivanje zbijenosti tla praćene su promjene u penetrometarskom otporu, volumnoj gustoći i ukupnome porozitetu tla. Postupci uključuju deset prohoda traktora s pogonom na sva četiri kotača, snage motora 54,0 kW i mase 3560 kg (1580 kg na prednjoj osovini i 1980 kg na stražnjoj osovini, međuosovinskoga razmaka 2,41 m). Na traktoru su bili dijagonalni pneumatici, sprijeda 11.2-24, a straga 16.9-30, s tlakom od 160 kPa i 100 kPa. Brzina kretanja traktora tijekom prohoda preko pokusnih parcela bila je 5,0 km h-1. U usporedbi s početnim stanjem tla, svaki prohod traktora prouzročio je povećanje penetrometarskog otpora na svim dubinama, a prosječno povećanje, ako se računaju svi slojevi, bilo je 9,8, 18,5 i 26,1% nakon jednog, pet i deset prohoda. Volumna se gustoća također povećala nakon prohoda traktora, ali je povećanje u postocima bilo manje. Prosječno povećanje, u usporedbi s početnim stanjem, bilo je 3,6, 9,5 i 12,9% nakon jednog, pet i deset prohoda. Ukupni se porozitet tla smanjio nakon prohoda traktora, a prosječno je smanjenje iznosilo 4,5, 16,5 i 20,8% nakon jednog, pet i deset prohoda traktora

UTJECAJ RAZLIČITIH SUSTAVA OBRADE TLA U PROIZVODNJI KUKURUZA, OZIME PŠENICE I SOJE NA LESIVIRANOM TLU SJEVERO-ZAPADNE SLAVONIJE

The paper presents comparison of three soil tillage systems in maize, winter wheat and soybean growing on anthropogenic Albic Luvisol in north-west Slavonia, Croatia, during 1996-1999. Tillage systems and implements were: 1. conventional system (CT)-plough, disc-harrow and combined implement, 2. conservation system (RT)-chisel plough and multitiller, 3. no-till system (NT). The aim of testing was comparison of different tillage systems energy requirement and its influence on yield. Results indicate that conventional tillage (CT) system was the greatest energy consumer with 1813.10 MJ ha-1. Comparing to conventional tillage (CT) system, conservation (RT) system with chisel plough and multitiller spent 1133.14 MJ ha-1or 37.5 % less, while no-till (NT) system required even 85.1 % less energy or 270.13 MJ ha-1. In the first season the greatest yield of maize, 7.78 Mg ha-1, achieved conventional tillage (CT) system while next to it was conservation (RT) system with 7.77 Mg ha-1. No-till (NT) system achieved 7.56 Mg ha-1. Second season the greatest yield of winter wheat, 5.89 Mg ha-1, achieved conservation tillage (RT) system. Next to it was conventional (CT) system with 5.75 Mg ha-1, while no-till (NT) achieved 5.73 Mg ha-1. Third season the greatest yield of soybean, 2.71 t ha-1, achieved conservation tillage (RT) system again, while next to it was conventional (CT) system with 2.64 Mg ha-1. No-till (NT) achieved 2.61 Mg ha-1.Rad prikazuje rezultate istraživanja primjene tri (3) različita sustava obrade tla u proizvodnji soje, ozime pšenice i kukuruza na antropogeniziranom lesiviranom tlu zapadne Slavonije, u vremenu 1996-1999. godine. Testirani sustavi obrade su: 1. konvencionalni sustav (CT)-plug, tanjurača i kombinirano oruđe, 2. konzervacijski sustav (RT)-rovilo i multitiller, te 3. nulta obrada (NT)-no-till sijačica. Cilj istraživanja bila je usporedba utroška energije različitih sustava obrade tla i njihov utjecaj na prinos uzgajanih usjeva. Konvencionalni sustav (CT) obrade tla najveći je potrošač energije sa 1813.10 MJ ha-1, dok konzervacijski sustav (RT) iziskuje 37.5 % manje, a nulta obrada (NT) čak 85.1 % manje energije po hektaru. Najveći prinos kukuruza od 7.78 Mg ha-1 ostvaren je konvencionalnim sustavom, ali gotovo identičan rezultat s 7.77 Mg ha-1 konzervacijskim (RT) sustavom. Nultim (NT) sustavom obrade ostvaren je prinos kukuruza od 7.56 Mg ha-1. U drugoj eksperimentalnoj godini najveći prinos ozime pšenice od 5.89 Mg ha-1 ostvario je konzervacijski (RT) sustav obrade. Slijedeći po rezultatu je konvencionalni sustav (CT) s 5.75 Mg ha-1, te nulti (NT) sustav obrade s 5.73 Mg ha-1. U trećoj je godini najveći prinos soje od 2.71 Mg/ha ostvario je konzervacijski (RT) sustav, a slijede konvencionalni (CT) sustav s 2.64 Mg ha-1 i nulti (NT) sustav obrade s 2.60 Mg ha-1