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 Dolná Malanta (Slovakia) in 2019. Biochar was applied and re-applied at the rates of 0, 10 and 20 t ha−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−1, respectively. We found that biochar applied at 20 t ha−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—the largest after re-application of biochar at a dose of 20 t ha−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.

Climate change is affecting all sectors of human activities worldwide, including crop production. The aim of the paper was to evaluate the average daily air temperatures measured at one hundred meteorological stations across Slovakia in 1961–2010 and calculate the maximum length of the vegetation period for Solanum lycopersicum L., Brassica oleracea L. var. capitata and Daucus carota L. Future trends predictions of the temporal and spatial development across the duration of the vegetation period in Slovakia were elaborated for decades 2011–2020, 2041–2050, 2071–2080 and 2091–2100. Our results show that there was an earlier start to the vegetation period in spring and a later termination in autumn for past 30 years. There is a predicted trend of prolongation of the maximum duration of the vegetation period up to 20 days (Solanum lycopersicum L., Brassica oleracea L. var. capitata) and 15 days (Daucus carota L.) in comparison with the refence decade 2001–2010. The maximum vegetation period duration will extend from the south of Slovakia towards the north of the country. The predicted potential increase in crop vegetation periods will be limited by other constraints such as the availability of arable land and soil water availability.

There are many methods used for soil water content measurement which we can divide into direct gravimetric methods from using soil samples or indirect methods that are based on the measurement of another soil property which is dependent on soil moisture. The paper presents the findings of volumetric water content measurements with gravimetric and time domain reflectometry (TDR) methods. We focused on four variants in the field experiment in Dolná Malanta (Slovakia): control variant (B0+N0), variant with biochar at dose 20 t.ha−1 without N fertilizer (B20+N0), variant with biochar 20 t.ha−1 and N fertilizer 160 kg.ha−1 (B20+N160) and variant with biochar 20 t.ha−1 and N fertilizer 240 kg.ha−1 (B20+N240). TDR is nowadays a well-established dielectric technique to measure volumetric water content; however, its accuracy is influenced by high concentration of salts in soil. In this paper, we evaluated the effect of added N fertilizer on the measuring accuracy of HydroSense II device that is operating under the TDR principle.

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).

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 purpose of the paper was to show cognition from the theory of climate change. The map outputs of these changes offer the climate data from basic elements and characteristics of the energy balance in terms of the current state as well as the trends and assumptions of their future changes in Slovakia. For these agroclimatic analyses, 100 climatic stations in Slovakia spread out to cover all agricultural regions, up to 800 m above sea level, have been selected. Our analyses are related to the period of years 1961-2010, when measurements and observations were the most homogeneous. The future trends and map outputs of future climate change were determined with the mathematic-statistical methods to the 2035, 2050, 2075-and 2100-year horizons. This study presents the impact of the climate change on the temperature conditions in Slovakia. The temperature changes (average, maximum and minimum temperature) were analysed with forecasts up to year 2100. The forecasts for the 2100-year horizon indicate increasing of the average annual temperature on average by about 2.0°C, maximum temperature on average by about 2.0°C and minimum temperature on average by about 2.5-3°C in comparison to the present.

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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.