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...
It is evident that the presence of organic matters in soil considerably influences by its microbial oxidation to CO 2 the requirement for calcareous compounds as well as the necessary amelioration dose of lime to reduce incurred soil acidity as the impact of balanced buffering CO 2 -HCO 3 -system, the more labile the organic matters are. If we take into consideration that the content of soil water per hectare of topsoil is, at the total weight of 6 × 10 6 kg, approximately, in analyzed sandy-loam soils 1.2 × 10 6 litre, in the given experiment soil water is just able to use up to 220 kg CaCO 3 /ha for the fixation of free surplus CO 2 to the value of equilibrium CO 2 , at zero elution! From this process, even 300-400 kg water-soluble Ca(HCO 3 ) 2 result. Of course, the ion exchange and the buffering system of the soil have further requirements for Ca compounds. Consequently, an unambiguous conclusion is: doses of calcareous compounds cannot be calculated only with the aim of reducing soil acidity and consumption of Ca nutrient by plants as it is common in the other nutrients. In a practical experiment in watersheds of nine Šumava brooks of the total area of 78.5 km 2 we studied changes in the stability of soil organic matters in the soils of these brooks in relation to variations in calcium carbonate equilibriums in waters from these watersheds in 1986-2004. The loss of the least stable fraction of soil organic matters, and the associated loss of the microbial activity of soils, were found to lead to a decrease in Langelier saturation index I s in the waters, hence to a reduction in water corrosivity against CaCO 3 , and so to a smaller need of liming to establish the calcium carbonate equilibrium in soil solutions even though exchange and active acidity of soil increased.
Two methods developed by Prof. Dohányos and Doc. Zábranská from ICT in Prague (A) and Oxi Top Control AN 12 measuring system manufactured by MERCK Company (B), were used to determine the maximum yield of biogas and methane and the maximum rate of biogas and methane production per unit weight of biomass using buffered and macro- and micro-nutrient enriched grass biomass as a substrate. Statistical evaluation proved that the Oxi Top Control method did not provide significantly lower or higher results than the other method that is considered standard. Although the Oxi Top Control AN 12 method has a higher variance of measured values than the standard method, it can be recommended as a project and operation method for its work comfort and expeditiousness.
Between 1999 and2002, the area at the foot of the Šumava Mountain Range was used to study the possibilities of harmonizing the productive and non-productive performance offered by permanent grassland. This paper presents the possibilities of Taraxacum officinale control within the permanent grassland covers (of the Lolio-Cynosuretum association). In an effort to reduce the cover rate of this species, it seems appropriate to reduce its use frequency. In the vegetation covers mowed three times a year the Taraxacum officinale reduction may be facilitated with the 100 N + PK dose application.
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