We performed 28-day mesophilic fermentation of a mixture of pig slurry and primary (raw) sludge from the sedimentation stage of a wastewater treatment plant at a 1:1 ratio. The components and the original and fermented mixture of slurry and sludge were subjected to acid hydrolysis. Dry matter of the solid phase of both components and both mixtures was incubated with sandy-loamy Cambisol at a weight ratio 3:1 at 25°C for 20 weeks; in 14-day intervals lipids, crude protein, hemicelluloses, cellulose, lignin, total nitrogen and hot-water-insoluble solids were determined. Changes in ion-exchange and buffering capacity of the test materials were recorded. Labile organic matters were determined after 20 weeks of incubation. Liquid fractions of both components and their mixtures were analysed before and after anaerobic fermentation. It was concluded that beneficial effects of wastes as fertilisers from anaerobic digestion could be attributed to their liquid fraction. After anaerobic digestion the solid fraction of these wastes has relatively increased ion exchange capacity as well as buffering capacity but it is very stable, hardly degradable organic matter, and therefore it cannot play the role of organic matter in soil. This is the reason why it should not be considered as an organic fertiliser.

The objective of the present paper is to contribute to the evaluation of quantity and quality of non-humified part of soil organic matter (SoM). in samples of soil organic matter from the humus profile of Šumava forest soils and forest meadows, taxonomically designated as mor and moder forms, the fractions of labile soil carbon C cws , C hws , C PM and fraction of stable carbon represented by carbon of humus acids C Ha and C Fa were determined. organic matter of samples was fractionated according to the degrees of hydrolyzability by two different methods in particle-size fractions of 2.00-0.25 mm and < 0.25 mm. The quality of labile fraction C hws was expressed on the basis of reaction kinetics as the rate constant of biochemical oxidation K bio and rate constant of chemical oxidation K chem of the first order reaction from a reduction in the concentration of C-compounds. The highest values of labile forms of carbon were determined in samples with the least favorable conditions for transformation processes of SoM, and these samples also had the highest content of labile forms in hydrolyses by both methods and the most labile fractions at the same time. The degree of SoM humification was strictly indirectly proportional to the lability of SoM and its hydrolyzability. The quality of labile fraction C hws can be expressed by both K bio and K chem while the sensitivity of K bio is higher but the reproducibility of K chem is better. K bio corresponds with the degree of SoM transformation, K chem with the proportion of C PM in total C ox .

We tested the procedure of combined phytomass utilization Integrated Generation of Solid Fuel and Biogas from Biomass (IFBB) proposed for ensiled grass matter from the aspect of suitability of its use for a typical substrate of new Czech biogas stations, a mixture of cattle slurry, maize silage and grass haylage. The agrochemical value of the liquid phase from a biofermenter was also evaluated. We concluded that this procedure is suitable for the tested substrate and improves the agrochemical value of a fugate from biogas production. By chlorine transfer to the liquid phase, it enables to use the solid phase as a material for production of solid biofuels with a reduced threat of the generation of polychlorinated dioxins and dibenzofurans during combustion. However, the concentration of mineral nutrients in the liquid phase during IFBB procedure is extremely low after anaerobic digestion as a result of dilution with water, and so its volume value is negligible.

A new method was proposed that complements the value of active carbon in the soil expressed as hot-water soluble carbon C hws . The method is based on vacuum measurements of biochemical oxygen demand (BOD) of soil suspensions using an Oxi Top Control system manufactured by the WTW Merck Company that is destined for hydrochemical analyses of organically contaminated waters. Measurements will provide BOD values for particular days of incubation; total limit BOD t can be determined from these values, and it is possible to calculate the rate constant k 1 of mineralization of a decomposable part of soil organic matter. It is typical of soil organic matter (SOM) of a given soil sample and comparable with the BOD 5 :COD (chemical oxygen demand) ratio that is used to evaluate degradability of water organic contamination in hydrochemical analytics.Keywords: soil organic matter (SOM); decomposable part of SOM; mineralization kinetics; analytical method Soil organic matter (SOM) undergoes short-and longterm transformations in the soil. Long-term transformations last for tens of years and establish a new dynamic equilibrium. The amount of long-time unchangeable inert soil organic matter can be determined from unfertilized parcels of long-term trials. There exists a relation between the content of fine particles in soil (below 6.3 µm) and the amount of carbon in inert soil organic matter (Körschens 1980). A difference between total content of C org in farmed soils and the calculated content of inert carbon is considered as carbon of decomposable organic matters C dec . Under a dynamic equilibrium a portion of SOM is mineralized during one growing season, and the same portion is newly formed. This portion of soil organic matter is considered as active and its carbon is active organic carbon. To determine the active carbon the easiest and most suitable method is determination of so called hot water extractable C hws (Körschens et al. 1990, Schulz 1990, Weigel et al. 1998). Carbon C dec of decomposable organic matters was studied by Kubát and Vrzáková (1984), Kubát and Veselý (1986). Schulz (1997) expressed the relation between decomposable C dec and C hws by the equation C dec = 15C hws . C dec and/or C hws are important as energy substrates for soil microorganisms and material for mineralization, therefore they belong to the main traits of soil productivity. Optimum value of C hws in basic types and textures of soils is 0.3-0.6 g/kg, i.e. 0.03-0.06%.Through their enzymes soil microorganisms are able to mineralize less soluble carbon sources while the rate of this process is different. In the present paper we tried to determine C dec of decomposable organic matters more exactly employing reaction kinetics of their mineralization.For this purpose we used biochemical oxygen demand (BOD), a current method of hydrochemical analytics for determination of organic contamination; it is regularly carried out as five-day incubation (Czech designation is BSK and BSK 5 ) or as BOD t (BSK c ) -i.e. the limit value of total biochemi...

The labile fraction of soil organic carbon (SOC) in terms of its quantity is a sensitive but dynamic indicator of the reactive agent in soils. If it is to be considered as a feature of soil quality, the value of its quantity should be completed by data on its quality. It can be expressed by the value of the rate constant of microbial oxidation k bio of this fraction or by data on chemical stability during hydrolysis or oxidation. If the quality of SOC labile fraction is not determined, at least the ratio of C MIC : C org should be given. The adjustment of soil acidity increases the microbial activity of soils, therefore the quantity of SOC labile fraction decreases and at the same time k bio decreases proportionately to the increasing stability of soil organic matters. During a 5-year period after the liming the soils acidify again and this process passes the faster the lesser their ion exchange capacity and buffering are. The quantity of the labile fraction of SOC raises again, its stability decreases and k bio raises again. The conversion pH value has secondary relevance.