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Samples of soils and surface waters were analysed in the umava foothills region in nine watersheds with an area 78.5 km 2 in 19861987 and in 2001. Lower intensity of fertilization and liming and other changes in Czech agriculture were found to result in a decrease in the content of cold and hot water soluble carbon (C w and C hws ) in the soil; the content of biologically decomposable matter expressed as BOD 5 and BOD t of water extract of soil also decreased. The values of rate constants k of BOD kinetics of soil suspension indicate that the most valuable fast decomposable organic matter in the soils of this region have practically been mineralized to HCO 3 , which are gradually eluted from soils and their increased amounts are present in surface waters. On the contrary, the transport of N-NO 3 decreased to 66.3% of the value in 1986, that of N-NH 4 + to 7.1% while the ratios C:N and N:P increased as a result of lower P elution in relation to lower N elution. COD Mn showing the proportion of readily decomposable matter increased. A decrease in conductivity, i.e. in the content of dissolved salts in waters, was highly significant. These results warn against an optimistic interpretation of surface water analyses that indicate positive impacts of farming intensity reduction on the landscape. The results in the umava foothills region demonstrate that a major part of the most valuable components of soil productivity, decomposable organic matter, has already been decomposed, so their content in the soil has decreased. Natural sources (roots, root exudates, plant residues) are not able to ensure an equilibrium balance of these valuable matters at a lower farming intensity.

We proposed a new method to determine the rate constant of biochemical oxidation of soil organic ma�ers that makes it possible to evaluate their stability by Spectroquant Merck BOD photometric tests; if smaller samplings are used and individual determinations are performed, it can replace the method of BOD vacuum measuring by an Oxi Top Control Merck system. The time and labour consumption of this vacuum method is sometimes criticised, but it has demonstrable work advantages for a large series of samples and so it is still recommended. The two methods are identical as for the correctness and coincidence of results and they do not differ by either lower or higher results and therefore we recommend the new method with photometric tests for smaller series of samples. For the high time and labour consumption we must warn against the use of traditional BOD dilution method with volumetric determination of oxygen for the determination of rate constants. MATERIAL AND METHODSTwo collection-testing samples of soils were used for the determinations: one sample with a higher content of organic matters, the other with a lower content and higher stability of these matters. These two different samples were analysed by a newly proposed method of photometric tests Spectroquant Merck BOD KT with the range of 0.5-3000 mg O 2 /l (cat. no. 100687) that is based on a modification of the traditional Winkler's method. We employed BOD standard for the preparation of 10 l of standard solution (cat. no. 100718) and BOD nutrient mixture with allylthiourea for 12 l of nutrient solution (cat. no. 100688). For each determination at least 4 oxygen reaction vessels for BOD determination (cat. no. 114663) were necessary. CHOD test with the range of 10-150 or 15-300 mg O 2 /l (cat. nos. 114540 and 114895) was used to determine the total amount of organic matters. These are cuvette, not reagent tests.Measurements were carried out in a Spectroquant NOVA 60 photometer that works with 12 filters by the diode field technique (reference ray technique), is connected to a PC with the software Windows Multi Achat II for data processing and has the memory capacity for 1000 data blocks. It has an Auto Select function for differentiation of tests according to the bar code and AQA (Analytical Quality Assurance) function.The two tested samples of the soils were analysed by the previously described method OXI Top Control WTW Merck .The procedure of sample preparation and the conduct of the cultivation process were the same as described in the cited paper. Because the photometric measurements are not accessible if the sample turns turbid, just before the photometric measurement the sample was drawn with a syringe and before the transfer into the cuvette of the apparatus it was filtered under an N 2 screen using an Anotop MERCK membrane filter of porosity 0.45 µm directly onto the perpendicularly upwards set syringe until air bubbles were removed from the filter. The spectrophotometer has a built-in function of "turbidity correction".The correctness of t...

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.

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.