Soil respiration rates before and during glucose decomposition in samples from the A0 horizon of podzolized forest soils were monitored with computerized equipment. Near infrared reflectance (NIR) spectra of the organic matter composition of the same samples were used to model the variation in basal respiration rate, substrate induced respiration (SIR) and lag time. Basal respiration rate was determined for intact sample cores, after sieving the samples, and after adjustment of the water content to 2.5 times the organic matter content. Multivariate regression with the Partial Least Squares algorithm was used in the modelling. Before sieving, 81.8% of the variation in basal respiration could be modelled by 15 NIR wavelengths measured on freeze-dried and milled soil. After sieving, 93.0-97.7% of the variation was explained by the same 15 wavelengths, which also explained 88.4% of the variation in SIR. 93.1% of the variation in lag time could be modelled by 83 NIR wavelengths measured on soil with a water content of 2.5 times the organic matter content.

DEUTSCH: Die mikrobielle Oxidation von Schwefel in Boeden ist im Hinblick auf die chemische Duengung von besonderer Bedeutung. Es werden verschiedene chemoheterotrophe Mikroorganismen aus indischen Terai-Boeden, vom Fusse des Himalaja-Gebirges, die dem Inceotisol-Halaquet-Bodentypen entsprechen, auf Saccharose-Natriumthiosulfat-Agarplatten isoliert. Es wurden Bakterien der Gattung Bacillus, Micrococcus und Streptomyces sowie Pilze der Art Penicillium und Aspergillus gewonnen. Die Bacillus-Spezies TSB5 und TSB6, das Streptomyces-Isolat TSA1 sowie die Aspergillus-Isolate TSF3 und TSF5 oxidierten Natriumthiosulfat bzw. L-Cystin am besten, wobei bei der anorganischen Schwefelverbindung die Schwefeloxidation wesentlich hoeher war als bei der organischen Schwefelverbindung.

In einer Uebersicht werden die Ueberlebensstrategien, die speziellen Schutzmechanismen und die Stoffwechselaktivitaeten von pflanzenpathogenen Mikroorganismen im Boden dargestellt. Die Beeinflussung ihrer Ueberdauerung im Boden durch aeusserliche Faktoren wird untersucht. Auf die Moeglichkeiten, gezielt die fuer zahlreiche wirtschaftlich bedeutsame Schaderreger wesentliche Infektionsquelle, Boden, auszuschalten, wird im Sinne eines integrierten Pflanzenschutzes hingewiesen.

The paper deals with the effect of different quantities of saturation mud and nitrogen on the frequency of individual groups of microorganisms in soil. The soil was used for growing wheat in a greenhouse. The frequency of microorganisms depended both on the quantity of saturation mud and doses of nitrogen. The application of saturation mud increased the frequency of microorganisms. The highest microorganism frequency was achieved with the highest quantity of saturation mud. The application of nitrogen decreased the frequency of microorganisms, while in combination with saturation mud it increased the frequency of microorganisms.

The nutristat, a substrate concentration-controlled continuous culture, was used to grow pentachlorophenol (PCP)-degrading microorganisms. The PCP concentration control system consisted of on-line measurement of the PCP concentration in the culture vessel with a tangential filter and a flowthrough spectrophotometer. With PCP concentrations between 45 and 77 micromolar, a stable situation was established in the nutristat, with an average dilution rate of 0.035 +/- 0.003 h-1. Compared with those of fed-batch cultures and chemostat cultures, the growth rates of microorganisms in the PCP nutristat were significantly higher, leading to considerable time savings in the enrichment procedure. In addition, PCP accumulation to severe inhibitory levels in the culture is prevented because the set point determines the (maximum) PCP concentration in the culture. The use of the nutristat as a tool for the growth of bacteria that degrade toxic compounds is discussed.

Graminaceous species can enhance acquisition of iron (Fe) by release of phytosiderophores mainly from apical root zones. However, phytosiderophores are readily degradable by microorganisms. To study the effect of rhizosphere microorganisms in Fe acquisition, maize plants were grown axenically or inoculated with a mixture of microorganisms in a limestone substrate supplemented with a small amount of Fe(III)-oxide. Axenic plants grew well without Fe deficiency symptoms and released considerable amounts of phytosiderophores. In contrast, inoculated plants showed severe symptoms of Fe deficiency chlorosis and much less phytosiderophores were detectable in the substrate. The severity of Fe deficiency chlorosis was strongly influenced by the mode of water supply either continuously by glass fibre wicks or by periodic short-term flooding. Inoculated plants became more chlorotic, when watered by flooding than plants watered by glass fibre wicks. This was suggested to be due to greater microbial degradation of phytosiderophores as a consequence of higher microbial population density in apical root zones, the sites of phytosiderophore release. To prove this hypothesis maize plants were grown in a silty loam soil. Short-term periodic flooding resulted in a uniform distribution pattern of rhizosphere microorganisms along the root axis, whereas in non-flooded plants the number of rhizosphere microorganisms was lower in apical root zones and increased sharply from 0-20 to 20-40 mm distance from the root apex. It is concluded, that in solid substrates a low population density of rhizosphere microorganisms in the apical root zone is of particular importance for efficient Fe acquisition by phytosiderophores in graminaceous species like maize.

The influence of nitrogen mineral fertilizers, depth and growth phase of sugar beet on the number of microorganisms from nitrogen cycle was investigated. All the groups of microorganisms were found in a great number and mostly in the ploughing layer (0-30 cm). The nitrogen fertilizers had the positive influence on the number of microorganisms when they were applied at the levels of 30, 60 and 90 kg/ha while the level of 120 kg N/ha had the inhibitory effect. The higher number of microorganisms was found in the middle and at the end of the vegetation period. The positive coorrelation was found between the number of nitrogen-fixing bacteria and parameters for sugar beet quality