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  • Author: Martin Juriga x
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Abstract

In this paper we investigate the effects of biochar alone and its reapplication and combination with N-fertilizer (1) on the soil pH, and (2) sorption parameters. The soil samples were taken during growing period in 2018 from plots with different biochar (first application in 2014 – A, reapplication in 2018 – B) at application rates: 0 t.ha−1 (B0 control), 10 t.ha−1 (B10) and 20 t.ha−1 (B20) and different nitrogen fertilization: N0 (no nitrogen) and N40 (40 kg.ha−1). Our results showed that the first application of biochar at the rate of 20 t.ha−1 (B20A) without N-fertilizer significantly increased the values of soil pH in H2O, soil pH in KCl, the sum of base cations (SBC) and cation exchange capacity (CEC) compared to control (B0). Similar effects were observed also after reapplication of biochar (B10B). All investigated parameters in fertilized control treatment (B0N40) were worst and the first application, as well as the reapplication of biochar with N, caused significant increase of soil pH in H2O, soil pH in KCl, SBC, CEC, BS and decrease of hydrolytic acidity.

Abstract

An interaction between the slope position and type of soil management practices could be one of the most important factor affecting several soil properties including soil structure. Therefore, we evaluated selected soil properties including soil structure parameters in relation to slope gradient and soil management practices between Trakovice and Bučany villages (western Slovakia). The sampling sites were located in two adjacent, gently sloping fields with a NW-SE orientation. The sites also differ in soil management type: Field No. 1 was used as arable land with intensive cultivation (IC) of crops, while a greening system (GS) had been established on Field No. 2. Soil samples were taken from five geomorphological zones at each slope: summit, shoulder, back-slope, toe slope and flat terrain under the slope. Results showed that soil pH, content of soil organic matter (SOM) and carbonates depended on land use of the slopes. In GS, the water-stable macro-aggregates (WSAma) 0.5–3 mm (favourable size fraction) displayed statistical significant quadratic polynomial trend along the slope gradient. In IC the values of mean weight diameter of dry sieved aggregates (MWDd) decreased significantly along the slope gradient, while in GS the opposite trend was observed. In IC significant correlations between carbonates content (r=-0.775, P<0.01), humic acids (HA) content (r=0.654, P<0.05), colour quotients of humic substances (r=-0.706, P<0.05), colour quotients of HA (r=-0.723, P<0.05) and MWDd were determined. In GS higher content of carbonates was followed by a decrease in content WSAma, MWDd, mean weight diameter of wet sieved aggregates (MWDw) and stability index of aggregates. At the same time stabile and labile soil organic matter improved soil structure parameters in GS.

Abstract

Nowadays, the operating nuclear reactors are able to utilise only 1 % of mined out uranium. An effective exploitation of uranium, even 60 %, is possible to achieve in so-called fast reactors. These reactors commercial operation is expected after the year 2035. Several design configurations of these reactors exist. Fast reactors rank among the so-called Generation IV reactors. Helium-cooled reactor, as a gas-cooled fast reactor, is one of them. Exchangers used to a heat transfer from a reactor active zone (i.e. heat exchangers) are an important part of fast reactors. This paper deals with the design calculation of U-tube heat exchanger (precisely 1-2 shell and tube heat exchanger with U-tubes): water – helium.

Abstract

The aim of this study was to investigate the usage of Dynamic Image Analysis for determination of size, shape and distribution of granules of microcrystalline cellulose, created by high shear granulation. A series of experiments was carried out to analyse the effect of process parameters on a created granule morphology. The amount of the granulation liquid and speed of the impeller have a significant effect on the median size granule value, the sphericity, the granule distribution width, but also on the granulation process yield.

Abstract

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.