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The formation of soil aggregates, including water-stable aggregates, is linked to soil organic matter (SOM). Biochar (B) is carbon-rich, which, in addition to storing carbon in a stable form for many years, has important benefits for soils and plants, but the mechanisms of soil structure formation after B and mineral fertiliser application are not sufficiently studied. For this reason, the study aimed to answer the following questions: How (1) the rate of B and (2) varying levels of nitrogen fertiliser (N) being applied to the soil affect the dynamics of soil aggregation due to the increase in the content of soil organic carbon, labile carbon in the bulk soil and in the content of water-stable aggregates (WSA) size-fractions. In 2014–2021, in Dolná Malanta (experimental site of Slovak University of Agriculture on silty loam Haplic Luvisol) during the growing seasons, soil samples were collected from all the B (0, 10 and 20 t ha–1) and N (0, 1st and 2nd level of N fertilisation) treatments. The results have shown that the highest values of many variables were associated with B20 treatment for all the N fertilisation levels. B compared to N more significantly affected the content of almost all the size-fractions of WSA. In all the treatments, the content of WSAma >5 mm, 5–3 mm, 3–2 mm and 1–0.5 mm in size was increasing over time – a yearly increase from 0.31 to 2.14% for 8-years. Based on the changes in the SOM content, WSA were divided into 3 groups: 1) Water-stable microaggregates (WSAmi < 0.25 mm), 2) Smaller size-fractions of water-stable macroaggregates (WSAma 1–0.25 mm), and 3) Medium and large fractions of WSAma (WSAma ≥1 mm).

Biochar application to agriculture soil has been recommended as a strategy to reduce increasing CO2 emission in the atmosphere and mitigate climate change. In this study, we evaluated the impact of two doses of biochar (10 and 20 t.ha−1) applied in 2014 and reapplied in 2018 combined with three fertilization levels (N0, N1, N2) on carbon dioxide emissions and selected physical and chemical soil properties in field conditions during spring season (April–June) in 2020. The field site is situated in the Nitra region of Slovakia (Malanta). The soil in the field was classified as a silt loam Haplic Luvisol. In this field research it was found that biochar application mostly in all treatments decreased cumulative CO2 emissions in rage from 4.2% to 30.4% compared to controls (B0N0, B0N2), except treatments where biochar was applied with lower level of N-fertilizer (N1) and treatment B20N0. According to our study results, it was confirmed that biochar can be a promising material for improving soil physical and chemical properties. Mainly, it has very good impact on soil pH, even after seven years of field experiment established. However, the response of soil CO2 fluxes to biochar application were regulated mainly by experiment length, biochar application rate, biochar properties, giving a new perspective for more comprehensive understanding on biochar.

Purpose This study investigates if a biochar application in 2014 and its reapplication in 2018 had affected the selected physical and hydrophysical soil properties of silty loam Haplic Luvisol at Dolná Malanta experimental site (Nitra, Slovakia) during the studied period of 2018–2020. Materials and methods Biochar was produced from cereal husks and paper fiber sludge by pyrolysis at temperature of 550 °C for 30 min and was applied to the soil in doses of 0, 10, and 20 t ha−1. The biochar treatments were combined with three levels of N fertilization (N0, N1, and N2). Results Biochar significantly decreased the bulk density up to − 12% and increased the soil porosity up to + 22% even 4–6 years after the biochar application. We also observed an increase in saturated hydraulic conductivity, which was reflected in better precipitation retention and a higher average soil water content by 12–15% depending on the fertilization level. Depending on the level of N fertilization, the interval of plant available water enlarged by 8–51% (10 t ha−1 of biochar), 18–21% (20 t ha−1 of biochar) after single biochar application, and by 18–34% (10 t ha−1 of biochar) and 19–31% (20 t ha−1 of biochar) after reapplication of biochar, which has positive implications regarding providing soil water to plants. Conclusions The results indicate that biochar amendments have the potential to substantially improve the soil water characteristics, and therefore, the quality status of silty loam agricultural soils.

Biochars, depending on the types of feedstocks and technological conditions of pyrolysis, can vary significantly in their properties and, therefore, it is difficult to predict biochar-induced effects on nitrous oxide (N2O) emissions from various soils, their physical properties and water availability. The objectives of this study were (1) to quantify effects of slow pyrolysis biochar (BC) and fast pyrolysis biochar (PYRO) on physical and hydro-physical properties of sandy soil (Haplic Arenosol) and clayey loam soil (Gleyic Fluvisol), and (2) to assess corresponding N2O emissions from these two soils. The study included a 63-day long laboratory investigation. Two doses of BC or PYRO (15 t ha−1 and 30 t ha−1) were applied to the soils in combination or without nitrogen fertilizer (NH4NO3, 90 kg N ha−1). The obtained results have shown a significant decrease in the bulk density of sandy soil after it was amended with either rate of BC or PYRO. Water retention capacity of the soils in all the treatments with BC or PYRO increased considerably although no changes was found in the soil water-filled pore space (WFPS) which was higher than 60%. BC was increasing N2O emission rates from the sandy soil treated with N fertilizer, and reducing N2O emission rates from the clayey loam soil treated with N fertilizer. PYRO was more efficient and was reducing N2O emissions from both fertilized soils, but for the sandy soil the reduction was statistically significant only at higher dose (30 t ha−1) of the biochar.

Biochar can affect CO2 emission and C sequestration from soils, but little is known about the effects of its re-application and interaction with easily accessible substrates. Since most agricultural soils are continuously reworked, understanding the mechanics of CO2 evolution as affected by soil amendments and their combinations may have important lessons for the global effort to combat climate change. In this study carried out in a controlled environment, we tested the short-term effects of biochar, and its re-application at different rates, on the production of CO2 emission and C accumulation in samples of arable soils. We used a loamy Haplic Luvisol as the substrate and added varying amounts of biochar and sources of easily accessible N and C. We observed CO2 evolution for 20 days at optimal temperature and moisture conditions. We found that in the control treatment with no biochar, the total potential respiration after the addition of (NH4)2SO4 (N) and glucose (G) was increased compared to basal respiration. The addition of biochar reduced CO2 emission in the control, N- and G-stimulated treatments by 12–22, 13‒24 and 2‒21%, respectively. Conversely, the application of biochar increased CO2 emission in the combined NG treatment. Application of biochar at a higher rate, as well as its re-application, increased soil organic carbon content and reduced emission of CO2 into the atmosphere.

Biochar application into soil has potential as a means for reducing soil greenhouse gas emissions and climate mitigation strategy. In this study, we evaluated the impact of two doses of biochar (10 and 20 t.ha−1) applied in 2014, combined with three fertilization levels (N0, N1, N2) on carbon dioxide (CO2) in field conditions during the growing season (April – October) in 2018. The field site is located in the Nitra region of Slovakia – Malanta. The soil in the field was classified as a silt loam Haplic Luvisol. There was not found any statistically significant (P 2 emissions, while the CO2 emissions increased with additional N-fertilizer. Biochar decreased (insignificantly) the daily and cumulative CO2 emissions only in the treatments without N-fertilization and in the treatment fertilized with higher level of biochar application (20 t.ha−1) and N-fertilizer (80 kg.N.ha−1). According to these results it can be concluded that the biochar applied to soil is not able to reduce CO2 emissions after four years of its application when it is combined with usual agriculture practices which include N-fertilization.

It was shown that the use of biochar provides many benefits to agriculture by improving the whole complex of soil properties, including soil structure. However, the diverse range of biochar effects depends on its physicochemical properties, its application rates, soil initial properties etc. The impacts of biochar, mainly its reapplication to soils and its interaction with nitrogen in relation to water-stable aggregates (WSA) did not receive much attention to date. The aims of the study were: (1) to evaluate the effect of initial application (in spring 2014) and reapplication (in spring 2018) of different biochar rates (B0, B10 and B20 t ha−1) as well as application of biochar with N-fertilizer (40 to 240 kg N ha−1 depending on the requirement of the cultivated crop) on the content of WSA as one of the most important indicators of soil structure quality, (2) to assess the interrelationships between the contents of soil organic matter (SOM) and WSA. The study was conducted in 2017–2019 as part of the field experiment with biochar on Haplic Luvisol at the experimental station of SUA in Nitra, Slovakia. Results showed that initial application as well as reapplication of biochar improved soil structure. The most favorable changes in soil structure were found in N0B20B treatment (with biochar reapplication) at which a significantly higher content of water-stable macro-aggregates (WSAma) (+15%) as well as content of WSAma size fractions of > 5 mm, 5–3 mm, 3–2 mm and 2–1 mm (+72%, +65%, +57% and +64%, respectively) was observed compared to the control. An increase in SOM content, due to both, initial biochar application and its reapplication, significantly supported the stability of soil aggregates, while organic matter including humic substances composition did not.

Current biochar application in the global agronomic practice focuses firstly on economic profits. In this paper, we would like to draw attention to our results and experience from the economic assessment of the agronomic effect of applied biochar through the generated crop yields. The results come from a field experiment (locality Dolná Malanta, Slovakia, silt loam Haplic Luvisol – the most intensively used soil in the Slovak Republic for agricultural purposes), where a biochar experiment was established in 2014. Based on our data, it is evident that both the application of biochar and its application in combination with N-fertilisation in field conditions at current realization prices of commodities in individual years and high input costs are still unprofitable. However, we emphasize that from an economic point of view of the stand ard agronomic practice.

The paper presents evaluation of the calibration method using side-by-side direct gravimetric and indirect time domain reflectometry (TDR) for soil moisture measurements to improve TDR measurement accuracy. Measurements were carried out at the experimental site Dolná Malanta (Slovakia) in 2017. Two non-fertilized treatments – without biochar (B0 + N0) and with biochar at 20 t·ha−1 (B20 + N0) – and two fertilized treatments – with biochar at 20 t·ha−1 and N fertilizer at dosages of 160 kg·ha−1 (B20 + N160) and 240 kg·ha−1 (B20 + N240) – were used in this study. The study also investigates the relationship between both used methods of soil water content determination. A strong correlation between both methods was observed. In case of (B0 + N0); (B20 + N0); (B20 + N160); and (B20 + N240), it was 0.93; 0.97; 0.97; and 0.98, respectively. However, it is assumed that the TDR probe may show errors in the results without prior calibration. It was observed that the accuracy of TDR device was lower for fertilized treatments in contrast to the gravimetric method and non-fertilized treatments. It is assumed that the higher measurement inaccuracy might be increased by salt concentration in the soil as a result of applied N fertilizer.

The objectives of the study were to: (1) assess the strength of associations of direct CO2 and N2O emissions with the seasonal variations in the relevant soil properties under both tillage systems; 2) evaluate how CT and RT affect magnitudes of seasonal CO2 and N2O fluxes from soil. Field studies were carried out on plots for conventional tillage (up to 0.22–0.25 m) and reduced tillage (up to 0.10–0.12 m) during the growing season and post-harvest period of red clover. The results showed that daily CO2 emissions significantly correlated only with soil temperature during the growing season under conventional and reduced tillage. Soil temperature demonstrated its highest influence on daily N2O emissions only at the beginning of the growing season in both tillage systems. There were no significant inter-system differences in daily CO2 and N2O emissions from soil during the entire period of observations. Over the duration of post-harvest period, water-filled pore space was a better predictor of daily CO2 emissions from soils under CT and RT. The conventional and reduced tillage did not cause significant differences in cumulative N2O and CO2 fluxes from soil.

The effect of a nitrogen enriched biochar mixed with compost (FBcCmp) in ratio 50:50 v/v on carbon dioxide (CO2) and nitrous oxide (N2O) emission from Haplic Luvisol was studied in a laboratory experiment. Biochar was produced from grain husks and paper fiber sludge and enriched with 10% ammonium sulfate solution; compost was generated from green waste, milk sludge and stone powder. Eight treatments were used in the experiment: control (Co), biochar (Bc), compost (Cmp), 10% ammonium sulfate solution(F) and their mixtures: Bc + Cmp, Bc + F, Cmp + F, and FBcCmp, which were applied to the soil at two rates equal to10 and 20 t ha−1(rate I and II), respectively. Direct fluxes of CO2 and N2O from the mesocosms were measured using the closed chamber technique. Application of FBcCmpin both rates significantly (P

During the last time a lot of studies focused on the effects of biochar application to agricultural soils and its effect on the soil properties. However only few information is known about the simultaneous impact of N-fertilizer combined with biochar to soil physical propersies such as: soil moisture, soil temperature, bulk density and water filled pore space. Therefore the aim of this study was to evaluate the changes in the soil physical properties of a silty loam Haplic Luvisol affected by the biochar application and its combination with N fertilizer during the years 2014-2016 (Experimental site of SUA-Nitra, Dolná Malanta, Slovakia). The field experiment was carried out in 2014 with different biochar application doses (0, 10 and 20 t ha-1) and different rate of N fertilization (0, 1st and 2nd level of N fertilization). The results showed that the both biochar amendment and biochar with N fertilizer increased on average the soil moisture in range of 1 to 15%. The higher rate of biochar resulted in higher soil moisture in all treatments with biochar in the following order B0 (14.9) < B10 (15.1) < B20 (16.2) as well as in biochar in combination with N fertilization: B0N1 (14.6) < B10N1 (15.7) < B20N1 (16.2) as well as B0N2 (14.8) < B10N2 (15.8) B10N1 (1.47) > B20N1 (1.44) as well as B0N2 (1.51) > B10N2 (1.47) > B20N2 (1.39) during years the studied period (2014-2016).

Greenhouse gases such as N2O and CO2 are formed in microbiological processes of nitrification and denitrification and also governed by microbial decomposition of soil organic matter (SOM) plant residues. A key factors influencing these processes are temperature and soil moisture. Therefore the objectives of this study were to: (1) evaluate the seasonal variations in SOM content, temperature, water-filled pore space (WFPS) and mineral nitrogen content under conventional tillage (CT) and reduced tillage (RT) system, and (2) assess the direct CO2 and N2O emissions associated with the seasonal variations in the soil properties under both tillage systems. An experiment was carried out in a randomized blocks with two different tillage system: CT and RT in a Haplic Luvisol (loamy) covering the growing season of spring barley. Each block included treatments: no mineral fertilizers; mineral fertilizers; mineral fertilizers plus plant residues. Overall, the SOM content and temperatures were insignificantly higher in the plough layers of RT than CT during the entire period of study. Soil moisture content (SMC) and WFPS were insignificantly higher in CT than RT. The application of mineral fertilizers resulted in a significant increase of mean NO3− concentrations only in the plough layers of CT. SMC was a stronger driving factor of mean daily CO2 emissions in all treatments, while variations in soil temperatures and SMC were jointly responsible for changes in mean daily N2O emissions in all the treatments of CT and RT. The postponed highest peaks of mean daily N2O emissions from RT were observed under aerobic soil conditions several days after the heavy rainstorm. The cumulative CO2 and N2O fluxes were insignificantly higher from CT than RT over the entire period of study.

Recent findings of changing climate, water scarcity, soil degradation, and greenhouse gas emissions have brought major challenges to sustainable agriculture worldwide. Biochar application to soil proves to be a suitable solution to these problems. Although the literature presents the pros and cons of biochar application, very little information is available on the impact of repeated application. In this study, we evaluate and discuss the effects of initial and reapplied biochar (both in rates of 0, 10, and 20 t ha−1) combined with N fertilization (at doses of 0, 40, and 80 kg ha−1) on soil properties and N2O emission from Haplic Luvisol in the temperate climate zone (Slovakia). Results showed that biochar generally improved the soil properties such as soil pH(KCl) (p ≤ 0.05, from acidic towards moderately acidic), soil organic carbon (p ≤ 0.05, an increase from 4% to over 100%), soil water availability (an increase from 1% to 15%), saturated hydraulic conductivity (an increase from 5% to 95%). The effects were more significant in the following cases: repeated rather than single biochar application, higher rather than lower biochar application rates, and higher rather than lower N fertilization levels. Initial and repeated biochar applications, leading to N2O emissions reduction, can be related to increased soil pH(KCl).

Biochar amended soil (BAS) has emerged as a sustainable and alternate material as a final cover system for landfills. This final cover is often subjected to change in matric suction due to seasonal change in evapotranspiration rates. The water retention characteristics, gas permeability and water infiltration vary for unsaturated soil depending on the suction in the soil. Main objective of this study was to investigate these unsaturated soil properties of BAS which are of major concern in landfill cover functioning. The biochar was produced from water hyacinth inside an in-house pyrolysis unit and mixed with a silty sand at 5% application rate. Water retention capacity increased with biochar amendment to silty sand. The air entry value increased by almost 100%, while the desorption rate marked by n parameter had no significant change, which was attributed to entrapped clay particles within the biochar and consequent alteration of soil porosity. Beyond suction range of 1 MPa, gas permeability of BAS decreased by almost 50% as compared to bare soil. This may be due to suppression of desiccation cracks in biochar amended soil. Infiltration rate was found to be relatively higher in case of biochar amended soil in comparison to bare soil. However, infiltration rate at different suction range were in same order, indicating marginal change in soil infiltration rate for actual field application.

Due to climate change the productive agricultural sectors have started to face various challenges, such as soil drought. Biochar is studied as a promising soil amendment. We studied the effect of a former biochar application (in 2014) and re-application (in 2018) on bulk density, porosity, saturated hydraulic conductivity, soil water content and selected soil water constants at the experimental site in Doln&aacute, Malanta (Slovakia) in 2019. Biochar was applied and re-applied at the rates of 0, 10 and 20 t ha&minus, 1. Nitrogen fertilizer was applied annually at application levels N0, N1 and N2. In 2019, these levels were represented by the doses of 0, 108 and 162 kg N ha&ndash, 1, respectively. We found that biochar applied at 20 t ha&ndash, 1 without fertilizer significantly reduced bulk density by 12% and increased porosity by 12%. During the dry period, a relative increase in soil water content was observed at all biochar treatments&mdash, the largest after re-application of biochar at a dose of 20 t ha&ndash, 1 at all fertilization levels. The biochar application also significantly increased plant available water. We suppose that change in the soil structure following a biochar amendment was one of the main reasons of our observations.

The paper presents the comparison of soil particle size distribution determined by standard pipette method and laser diffraction. Based on the obtained results (542 soil samples from 271 sites located in the Nitra, V&aacute, h and Hron River basins), regression models were calculated to convert the results of the particle size distribution by laser diffraction to pipette method. Considering one of the most common soil texture classification systems used in Slovakia (according to Nov&aacute, k), the emphasis was placed on the determination accuracy of particle size fraction &lt, 0.01 mm. Analysette22 MicroTec plus and Mastersizer2000 devices were used for laser diffraction. Polynomial regression model resulted in the best approximation of measurements by laser diffraction to values obtained by pipette method. In the case of particle size fraction &lt, 0.01 mm, the differences between the measured values by pipette method and both laser analyzers ranged in average from 3% up to 9% and from 2% up to 11% in the case of Analysette22 and Mastersizer2000, respectively. After correction, the differences decreased to average 3.28% (Analysette22) and 2.24% (Mastersizer2000) in comparison with pipette method. After recalculation of the data, laser diffraction can be used alongside the sedimentation methods.

In the agricultural sector, the soil's physical and hydrological properties become a limiting factor in achieving sufficient crop yields. Biochar has emerged as a significant source of organic carbon and a tool for its sequestration and there are identified significant relationships between soil agricultural properties induced by biochar application with that of soil physical and hydrological properties. However, underlying mechanisms for changes in some physical and hydrological properties of the soil are not fully understood due to insufficient data resulting in a poor understanding of the interconnection among properties in biochar substrates amended soils. Therefore, we studied the impact of two different biochar substrates (BS: BS1 – biochar blended with farmyard manure, and BS2 – biochar blended with farmyard manure and digestate) at two rates (10 and 20 t ha−1) combined alone and with additional fertilization (F) on two contrasting soils. The two contrasting soils included a sandy Arenosol, and a loamy Chernozem in south-western Slovakia. The changes in soil physical properties and interrelationships between soil pH, sorption capacity, soil organic matter (SOM), humic substances (HS), and physical properties was regularly monitored in the field for a three-year period (2018–2020). The results showed that biochar substrates had different effects with dependence on soil textures. In sandy soil, BS improved soil properties such as pore size distribution, soil-air content, and water regimes, including water retention capacity (WRC), and soil structure. The most significant effects were determined in the case of BS compared to BS + F, and in the case of 20 than 10 t ha−1 as well as in BS1 than BS2 in sandy soil. In loamy soil, compared to the control, the volume of non-capillary pores (Pnc) values decreased significantly (by 29%) in the BS1 10 t ha−1 treatment, while in the case of BS + F a significant decrease in Pnc was observed after application of both rates of BS1 compared to the fertilized control. For the BS1 + F, compared to the fertilized control, the soil water storage (SWS) increased significantly by 15 and 14% at 10 t ha−1 and 20 t ha−1, respectively. Overall, the soil structure was better in loamy than sandy soil and therefore the effect of BS was not as pronounced in loamy soil as it was in sandy soil. The number of correlations between soil pH, sorption capacity, SOM, HS, and soil physical properties decreased in the following order: loamy soil > sandy soil; BS + F > BS treatments; BS1 > BS2, and at a rate of 20 t ha−1 > at a rate of 10 t ha−1.

During the last decade, biochar has captured the attention of agriculturalists worldwide due to its positive effect on the environment. To verify the biochar effects on organic carbon content, soil sorption, and soil physical properties under the mild climate of Central Europe, we established a field experiment. This was carried out on a silty loam Haplic Luvisol at the Malanta experimental site of the Slovak Agricultural University in Nitra with five treatments: Control (biochar 0 t ha−1, nitrogen 0 kg ha−1); B10 (biochar 10 t ha−1, nitrogen 0 kg ha−1); B20 (biochar 20 t ha−1, nitrogen 0 kg ha−1); B10+N (biochar 10 t ha−1, nitrogen 160 kg ha−1) and B20+N (biochar 20 t ha−1, nitrogen 160 kg ha−1). Applied biochar increased total and available soil water content in all fertilized treatments. Based on the results from the spring soil sampling (porosity and water retention curves), we found a statistically significant increase in the soil water content for all fertilized treatments. Furthermore, biochar (with or without N fertilization) significantly decreased hydrolytic acidity and increased total organic carbon. After biochar amendment, the soil sorption complex became fully saturated mainly by the basic cations. Statistically significant linear relationships were observed between the porosity and (A) sum of base cations, (B) cation exchange capacity, (C) base saturation.

Recent studies show that biochar improves physical properties of soils and contributes to the carbon sequestration. In contrast to most other studies on biochar, the present study comprise a long-term field experiment with a special focus on the simultaneous impact of N-fertilizer to soil structure parameters and content of soil organic carbon (SOC) since SOC has been linked to improved aggregate stability. However, the question remains: how does the content of water-stable aggregates change with the content of organic matter? In this paper we investigate the effects of biochar alone and in a combination with N-fertilizer (i) on the content of water-stable macro- (WSAma ) and micro-aggregates (WSAmi ) as well as soil structure parameters; and (ii) on the contents of SOC and labile carbon (CL) in water-stable aggregates (WSA). A field experiment was conducted with different biochar application rates: B0 control (0 t ha−1), B10 (10 t ha−1) and B20 (20 t ha−1) and 0 (no N), 1st and 2nd level of nitrogen fertilization. The doses of level 1 were calculated on required average crop production using the balance method. The level 2 included an application of additional 100% of N in 2014 and additional 50% of N in the years 2015–2016 on silty loam Haplic Luvisol at the study site located at Dolná Malanta (Slovakia). The effects were investigated after the growing season of spring barley, maize and spring wheat in 2014, 2015 and 2016, respectively. The results indicate that the B10N0 treatment significantly decreased the structure vulnerability by 25% compared to B0N0. Overall, the lower level of N combined with lower doses of biochar and the higher level of N showed positive effects on the average contents of higher classes of WSAma and other soil structure parameters. The content of SOC in WSA in all size classes and the content of CL in WSAma 3–1 mm significantly increased after applying 20 t ha–1 of biochar compared to B0N0. In the case of the B20N1 treatment, the content of SOC in WSAma within the size classes >5 mm (8%), 5–3 mm (19%), 3–2 mm (12%), 2–1 mm (16%), 1–0.5 mm (14%), 0.5–0.25 mm (9%) and WSAmi (12%) was higher than in B0N1. We also observed a considerably higher content of SOC in WSAma 5–0.5 mm and WSAmi with the B10N1 treatment as compared to B0N1. Doses of 20 t biochar ha−1 combined with second level of N fertilization had significant effect on the increase of WSAma and WSAmi compared to the B0N2 treatment. A significant increase of CL in WSA was determined for size classes of 2–0.25 mm and WSAmi in the B20N2 treatment. Our findings showed that biochar might have beneficial effects on soil structure parameters, SOC, CL in WSA and carbon sequestration, depending on the applied amounts of biochar and nitrogen.

Since biochar is considered to be a significant source of carbon, in this work we have evaluated the changes in soil organic matter (SOM) and soil structure due to application of biochar and biochar with N fertilization, and have considered the interrelationships between the SOM parameters and the soil structure. The soil samples were collected from Haplic Luvisol at the locality of Dolná Malanta (Slovakia) during 2017. The field experiment included three rates of biochar application (B0 - no biochar, B10 - biochar at the rate of 10 t ha-1, B20 - biochar at the rate of 20 t ha-1) and three levels of N fertilization (N0 - no nitrogen, N160 - nitrogen at the rate of 160 kg ha-1, N240 - nitrogen at the rate of 240 kg ha-1). The rate of biochar at 20 t ha-1 caused an increase in the organic carbon (Corg) content. The combination of both rates of biochar with 160 and 240 kg N ha-1 also caused an increase in Corg. In the case of B20 the extractability of humic substances carbon (CHS) was 17.79% lower than at B0. A significant drop was also observed in the values of the extraction of humic acids carbon (CHA) and fulvic acids carbon (CFA) after the addition of biochar at a dose of 20 t ha-1 with 160 kg N ha-1. However, both rates of biochar had a significant effect at 240 kg N ha-1. After application of 20 t ha-1 of biochar the content of water-stable macro-aggregates (WSAma) significantly increased compared to control. This rate of biochar also increased the mean weight diameter (MWDW) and the index of water-stable aggregates (Sw) and decreased the coefficient of vulnerability (Kv). The biochar at a rate of 20 t ha-1 with 240 kg N ha-1 the value of MWDW increased and value of Kv decreased significantly. The contents of Corg and CL correlated positively with WSAma, MWDW and Sw and negatively with WSAmi and Kv. The extraction of CHA and CFA was in negative relationship with MWDW. We conclude that the application of biochar and biochar combined with N fertilizer had a positive influence on SOM and soil structure.

The effects of biochar and biochar combined with N-fertilizer on the content of soil organic matter in water-stable aggregates were investigated. A field experiment was conducted with different biochar application rates: B0 control (0 t ha-1), B10 (10 t ha-1) and B20 (20 t ha-1) and 0 (no N), 1st and 2nd levels of nitrogen fertilization on silt loam Haplic Luvisol (Dolna Malanta, Slovakia), in 2014. The N doses of level 1 were calculated on required average crop production using balance method. Level 2 included additional 100% of N in year 2014 and additional 50% of N in year 2016. The effects were investigated during the growing seasons of spring barley and spring wheat in 2014 and 2016, respectively. Results indicate that the B20N2 treatment significantly increased the proportion of water-stable macro-aggregates (WSAma) and reduced water-stable micro-aggregates (WSAmi). Aggregate stability increased only in the B20N1 treatment. The B20N2 treatment showed a robust decrease by 27% in the WSAma of 0.5-0.25 mm. On the other hand, an increase by 56% was observed in the content of WSAma with fractions 3-2 mm compared to the B0N0 treatment. The effect of N fertilizer on WSAma was confirmed only in the case of the B10N2 treatment. The proportion of WSAma with fractions 3-2 mm decreased by 42%, while the size fraction of 0.5-0.25 mm increased by 30% compared to the B10N0 treatment. The content of WSAma with fractions 1-0.5 mm decreased with time. On the contrary, the content of WSAma with particle sizes above 5 mm increased with time in all treatments except the B10N2 and B20N2 treatments. A statistically significant trend was identified in the proportion of WSA in the B10N2 and B20N2 treatments, which indicates that biochar with higher application levels of N fertilizer stabilizes the proportion of water-stable aggregates. In all treatments, the content of soil organic carbon (SOC) and labile carbon (CL) in WSAmi was lower than those in WSAma. A considerable decrease of SOC in the WSAma >5 mm and an increase of SOC in WSAmi were observed when biochar was applied at the rate of 10 t ha-1. Contents of SOC in WSAmi increased as a result of adding biochar combined with N fertilizer at first level. CL in WSA significantly increased in all size fractions of WSA.References Abiven S., Hund A., Martinsen V., Cornelissen G., 2015. Biochar amendment increases maize root surface areas and branching: a shovelomics study in Zambia. Plant Soil, 342, 1-11. Agegnehu G., Bass A.M., Nelson P.N., and Bird M.I., 2016. Benefits of biochar, compost and biochar–compost for soil quality, maize yield and greenhouse gas emissions in a tropical agricultural soil. Sci. Tot. Environ., 543, 295-306. Angers D.A., Samson N., Legere A., 1993. 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We tried to determine whether a commercially available, amended biochar could potentially increase the growth and yield of spring barley ('Hordeum vulgare' L. var. Malz) on loamy soil located in western Slovakia in 2014. Treatments (n=15) with three replications consisted of a control, raw biochar (RB) (0, 10, 20 t ha-1) and nitrogen-enriched biochar+compost (EB) (0, 10, 20 t ha-1) application, combined with 3 levels of mineral fertilization (0, 40, 80 kg N ha-1). The plots (4 m x 6 m) were organized in randomized block design. We examined above and below-ground biomass, crop height, number of plants per m2, grain yield and plant canopy development determined from digital image-derived vegetation indices. The positive effect of biochar application on the plant canopy development was observed. In case of the vegetation index, the difference between the treatments and control rose in the following order at all fertilization levels (0, 40, 80 kg ha-1): control < RB (10 t ha-1) < RB (20 t ha-1) < EB (10 t ha-1) < EB (20 t ha-1). Ten and twenty t ha-1 of EB without fertilizer increased root biomass by 126 and 52%, and above-ground biomass by 62 and 36%, respectively. We conclude that a single EB application of 10 t ha-1 or 20 t ha-1 (even if applied without N fertilizer) can increase plant biomass on loamy Typic Hapludalfs at least in the first cropping season.

The study focuses on looking for answers to the following questions: 1. Is biochar application a suitable solution for reducing CO2 emissions? 2. What application rate significantly reduces CO2 production to the atmosphere? 3. Does have the application of enriched biochar a justification in relation to reducing CO2 production? The experiment was established on Haplic Luvisol at the experimental site of SUA in Nitra (Dolná Malanta), where we measured CO2 emissions from the soil to the atmosphere under the following treatments: different rates (0, 10, 20 t ha-1) of pure biochar (B0, B10 a B20) and enriched biochar (EB10, EB20) combined with different levels of mineral nitrogen at doses of 0, 40 and 80 kg ha-1 (N0, N40, N80). Overall, the average values of CO2 emissions were lower by 19.8 %, 13.3 %, 12.9 %, 9.4 % and 8.7 % in B10N0, B20N40, B20N0, B20N80 and B10N40 treatments as compared to B0N0 (control) during the studied period. On the other hand, the average values of CO2 were higher by 20% in B10N80 treatments as compared to control (B0N0). Application of enriched biochar whether individually (EB10N0, EB20N0) or with additional N (EB10N40, EB20N40, EB10N80, EB20N80) increased average CO2 by 29.7 %, 34.6 %, 36.0 %, 44.9 %, 45.8 % and 53.6 % as compared to control (B0N0). The cumulative CO2 emissions for the whole studied period (2014) were in the following order from the lowest one B10N0 < B20N0 < B20N40 < B20N80 < B10N40 < B0N0 (control) < B10N80 < EB20N40 < EB20N80 < EB10N80 < EB20N0 < EB10N0 < EB10N40.

Biochar usually has a large specific surface area, and due to this, it increases the sorption capacity of the soil where it was applied. The objectives of this study were to (i) quantify the effects of biochar and biochar in combination with N fertilizer on the soil sorption parameters and (ii) quantify the effects of soil organic matter on the sorption parameters after application of biochar with and without N fertilizer. The experiment was established on Haplic Luvisol at the locality of Dolna Malanta (Slovakia) in 2014. The soil samples were collected once a month from the depth 0–0.2 m during 2014 to 2016. The field experiment included three rates of biochar application (B0 = no biochar, B10 = biochar at the rate of 10 t ha−1, B20 = biochar at the rate of 20 t ha−1) and three levels of N fertilization (N0 = no nitrogen, N40 = nitrogen at the rate of 40 kg ha−1, N80 = nitrogen at the rate of 80 kg ha−1). Overall, the decrease of the average values of hydrolytic acidity due to biochar and biochar combined with N fertilization resulted on average in an increase of sum of basic cation (SBC), cation exchange capacity (CEC), and sorption capacity of soil organic matter (CECSOM) in all treatments. However, this effect was the most intensive in B10N40. Despite the fact that the average values of sorption parameters improved, its dynamics during the investigated period were different. A significant decrease in CEC was observed from 2014 to 2016 in all treatments, except B0N0 and B10N0. A stable trend in CECSOM was observed only in B10N40. Humic substances and humic acids had a statistically significant positive effect on the SBC, CEC, and CECSOM only in B20N0 treatment. Negative correlations between the above mentioned parameters were observed in B10N80 treatment. We conclude that the application of biochar and biochar combined with N fertilization had a positive influence on sorption parameters. However, its effects on SBC, CEC, and CECSOM decreased over time after its application.

An experiment of different management practices in a commercial vineyard, which was established in 2006 in the locality of Nitra-Dražovce, Slovakia on Rendzic Leptosol, was used to evaluate the dynamics of soil organic-matter parameters during the years 2008–2015. The following treatments were established: 1. G (grass without fertilisation as control), 2. T (tillage), 3. T+FYM (tillage + farmyard manure), 4. G+NPK3 (grass + 3rd intensity of fertilisation for vineyards: it means 125 kg/ha N, 50 kg/ha P, 185 kg/ha K), and 5. G+NPK1 (grass + 1st intensity of fertilisation for vineyards: it means 100 kg/ha N, 30 kg/ha P, 120 kg/ha K). The results showed that the soil-management practices in the vineyard significantly influenced the soil organic carbon in water-stable aggregates (SOC in WSA). The content of SOC in WSAma increased on average in the following order: T < G < G+NPK1 < G+NPK3 < T+FYM. Intensive soil cultivation in the T treatment resulted in a statistically significant build-up of SOC in WSAma at an average rate of 1.33, 1.18, 0.97, 1.22 and 0.76 g/kg/y across the size fractions > 5 mm, 5‒3 mm, 2–1 mm, 1–0.5 mm and 0.5–0.25 mm, respectively. The content of non-labile carbon reflected the contents of SOC in WSA. The highest labile carbon (CL) in WSAma, as compared to others, was found in T+FYM. Overall, application of higher NPK doses resulted in higher content of CL in WSAma compared with the lower applications of NPK. On the other hand, lower applications of NPK to soil increased the content of CL in WSAmi, as compared to G+NPK3.

Nowadays, there are various methods of plant biomass assessment available for the purposes of plant growth analysis. Visual plant coverage assessment is often subjective; the other methods are destructive or require purchasing some special devices. This paper presents the assessment of the possibilities and limitations of using digital images made by conventional digital cameras for the purposes of monitoring of the plant canopy development and weed distribution during a vegetation period using the example from the field experiment established on agricultural land in Malanta at the experimental site of the Slovak University of Agriculture. The study is focused on assessment of the effect of biochar application on gas emission, hydrophysical soil properties as well as plant response and yields and it was established in the spring of 2014. Downward images of corn (Zea maysL.) were taken during four sampling campaigns in the vegetation season 2015. Images were analysed by the BreedPix software that could estimate the portion of green fraction (count of green pixels) and thus the image-derived vegetation index (IDVI). According to the image analysis of photos taken during different sampling dates, it could be concluded that biochar addition had a positive effect on the plant growth (above ground biomass) since all treatments resulted in higher IDVIs at the end of the vegetative growth in comparison to control. Further, we assume that the increasing trend in the crop canopy growth was partially limited by competitive presence of weeds at the beginning of the study. According to our experience, we can recommend the software for temporal and spatial monitoring of agricultural crops development. The usage is limited to early growth stages. Moreover, it can be also used for assessment of the weed coverage.

The benefits of biochar application are well described in tropical soils, however there is a dearth of information on its effects in agricultural temperate soils. An interesting and little explored interaction may occur in an intensive agriculture setting; biochar addition may modify the effect of commonplace N-fertilization. We conducted a field experiment to study the effects of biochar application at the rate of 0, 10 and 20 t ha-1 (B0, B10 and B20) in combination with 0, 40 and 80 kg N ha-1 of N-fertilizer (N0, N40, N80). We followed nitrous oxide (N2O) emissions, analysed a series of soil physicochemical properties and measured barley yield in a Haplic Luvisol in Central Europe. Seasonal cumulative N2O emissions from B10N0 and B20N0 treatments decreased by 27 and 25% respectively, when compared to B0N0. Cumulative N2O emissions from N40 and N80 combined with B10 and B20 were also lower by 21, 19 and 25, 32%, respectively compared to controls B0N40 and B0N80. Average pH was significantly increased by biochar addition. Increased soil pH and reduces NO-3 content seen in biochar treatments could be the two possible mechanisms responsible for reduced N2O emissions. There was a statistically significant increase of soil water content in B20N0 treatment compared to B0N0 control, possibly as a result of larger surface area and the presence of microspores having altered pore size distribution and water-holding capacity of the soil. Application of biochar at the rate of 10 t ha-1 had a positive effect on spring barley grain yield.