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Swelling behavior and bioactivity of humic acids hydrogels
Kozelková, Aneta ; Hynšt, Jaroslav (referee) ; Sedláček, Petr (advisor)
This thesis deals with the study of the biological activity of humic substances. Based on the literature review preparation procedures were optimized in order to develop new hydrogel forms containing humic substances and biopolymers with high swelling capacity. Besides methodology for the rapid assessment of the biological activity obtained in laboratory conditions were designed and tested. The experimental part focused on characterization of hydrogel samples by means of routine physico-chemical methods, the main attention was paid to sorption of water and release of humic substances into solution. Then the prepared hydrogel materials were tested focusing on the growth effects on the maize. The absorption of mineral nutrients by the roots of plants were studied as well. The motivation of this work comes from the potential of agricultural and environmental applications of such hydrogel materials resulting in a renewal of previously exhausted organic content of soils and consequent interruption of substantial soil degradation.
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Production of CO2 from tillage and conservation-tillage fields
Červinská, Taťána ; Frouz, Jan (advisor) ; Hynšt, Jaroslav (referee)
Soil respiration was studied in situ, using an apparatus Li 8000, together with potential microbial respiration, microbial biomass, enzymatic activity and content of organic substances in soil at different depths in two types of agricultural technologies: the conventional tillage cultivated fields and the fields on which were farmed using soil conservation technologies, here were used minimization and no tillage technology. These areas were sown by oilseed rape in the first year and a pea in the second year of observation (2010 and 2011). Study was carried out on long term experimental plots, established in 1995, in Prague Ruzyně to estimate the impact of these agricultural technologies on the accumulation or loss of carbon from the soil. It was found that the fields under cultivation tillage had significantly higher CO2 flux from soil than in areas with soil conservation technologies. CO2 flux was also influenced by external conditions, especially temperature. Total microbial biomass did not differ between technologies. However, they differ in terms of organic matter content. Minimizing resulted in significantly higher organic carbon content than the remaining fields. Areas under soil conservation technologies had a significantly higher content of humic acids. Cultivated fields plowing, or soil...
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Swelling behavior and bioactivity of humic acids hydrogels
Kozelková, Aneta ; Hynšt, Jaroslav (referee) ; Sedláček, Petr (advisor)
This thesis deals with the study of the biological activity of humic substances. Based on the literature review preparation procedures were optimized in order to develop new hydrogel forms containing humic substances and biopolymers with high swelling capacity. Besides methodology for the rapid assessment of the biological activity obtained in laboratory conditions were designed and tested. The experimental part focused on characterization of hydrogel samples by means of routine physico-chemical methods, the main attention was paid to sorption of water and release of humic substances into solution. Then the prepared hydrogel materials were tested focusing on the growth effects on the maize. The absorption of mineral nutrients by the roots of plants were studied as well. The motivation of this work comes from the potential of agricultural and environmental applications of such hydrogel materials resulting in a renewal of previously exhausted organic content of soils and consequent interruption of substantial soil degradation.
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Symptomes of nitrogen excess in soil
Hynšt, Jaroslav ; Šimek, Miloslav
Nitrogen cycling is one of the most important processes on the Earth. Most of N transformations run in soil. Nitrogen usually enters the soil as occasional input in concentrated forms which means that it is often in excess or in deficit. However, deficit and excess of N have different value in different soils and ecosystems. For example, amount of N which causes significant impact on ecosystem of spruce forest is insufficient for the maize field. This suggests, that the amount of N in soil must be evaluated in context of the whole ecosystem. In N-limited ecosystems, most of N is stored in plant biomass and litter characterized by slow transformations. Productivity of ecosystem is low, but N is utilized with high efficiency. On the other hand, in conditions of high availability of N, losses take place. These differences are reflected in content of different fractions of soluble N in soil and different rates of their transformations.
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Nitrogen and carbon transformation processes in soil in permanent grasslands - research in cattle overwintering area
Šimek, Miloslav ; Hynšt, Jaroslav ; Čuhel, Jiří ; Elhottová, Dana ; Chroňáková, Alica ; Němcová, Anna ; Jirout, Jiří ; Krištůfek, Václav
Agricultural soils represent a significant source of greenhouse gases (carbon dioxide, nitrous oxide and methane). Pasture soils and especially overwintering areas receive large amounts of nutrients as animal excrements. Together with other effects, this creates good conditions for high rates of nitrogen and carbon transformations, and also for substantial losses in the form of gaseous metabolites. This paper informs on research of a specific model ecosystem – the cattle overwintering area. Research is focused either on the structure of soil microbial community and on its activities including the formation of gases in, and their emission from the soil to atmosphere.
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Emissions of greenhouse gases (N2O and CO2) from pasture soil as a result of activity of soil microbial community - preliminary results
Šimek, Miloslav ; Hynšt, Jaroslav ; Brůček, Petr ; Čuhel, Jiří
Cattle overwintering area was shown an important point source of N2O and CO2. The emissions of N2O were mostly directly related to the rate of animal impact as the greatest fluxes of N2O and the highest total cumulative N2O emissions as well were found at the most impacted site. The fluxes of N2O were however very variable in time and most of N2O was emitted during several short events in spring or in winter. Laboratory experiments suggested that total amount of nitrogen escaping from soil from impacted sites is much greater than indicated by field measurements of N2O fluxes and molecular nitrogen (N2) was shown as the main nitrogen gas. It is hypothesized that soil pH is a crucial soil factor controlling the mole fraction of N2O: under slightly alkaline conditions in severely impacted soils, denitrification is completed and most of nitrogen escapes from the soil as N2; under more acidic conditions, however, the activity of nitrous oxide reductase is partly reduced.
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Dynamics of N2O emissions after C and N amendments of soil at the cattle overwintering area
Hynšt, Jaroslav ; Brůček, Petr ; Čuhel, Jiří ; Šimek, Miloslav
Field experiments were carried out at the cattle overwintering area in South Bohemia, Czech Republic, focused on the emissions of N2O after soil amendments with nitrate and glucose. Emissions were estimated using a permanent static chamber technique. Nitrate and glucose amendments caused very sharp increases of N2O fluxes, which however diminished after 2-3 days. Total amount of N2O escaping the soil was related to the amount of N and C added, and was calculated to 1-15 kg N.ha-1 (0.2-3% of N applied). Emissions were heterogeneous, which is shown by great differences among the individual chambers. Emissions were variable in time and very probably were controlled by temperature, as they approximately followed the air and surface soil temperature patterns. Despite the timing of amendment application, peaks of emissions were always determined 6 hours after the amendments.
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