Determination of fungal biomass (FB) and FB-carbon (FB-C) from soil ergosterol concentration is difficult because of unknown ergosterol-to-fungal biomass (E-to-FB) conversion factors and inefficient ergosterol extraction methods. We applied a microwave-assisted extraction (MAE) and high performance liquid chromatographic (HPLC) procedure to measure ergosterol in soil samples. The E-to-FB conversion factors were determined in six species of fungi grown in vitro. The MAE method was fast and extracted up to nine times more soil ergosterol than a classical refluxing saponification method. Soil ergosterol was separated and quantified rapidly (< 10 min) by HPLC. Alternaria alternata, Chaetomium globosum, Fusarium oxysporum, Penicillum chrysogenum, Rhizopus stolonifer and Trichoderma harzianum isolated from soil and plant matrices were grown in batch. Ergosterol and biomass content were determined in mycelia harvested during the stationary and exponential phases of growth. Total mycelial ergosterol ranged from 180 to 2178 microgram, and total dry biomass ranged from 17 to 595 mg. Total ergosterol and fungal dry biomass were strongly associated (r2 = 0.95). The C content in mycelial mats averaged 43% (+/- 1.1; SD), and was similar among fungal species and growth phases. The analyses of variance showed that the E-to-FB ratio was similar among fungal species or growth phase. An average ergosterol concentration of 4 microgram mg-1 dry biomass was determined for the six species of fungi, which gave a conversion factor of 250 microgram dry biomass microgram-1 ergosterol. The MAE method recovered an average of 62% (+/- 11%, SD) of the ergosterol added in mycelial mats to soils prior to extraction, and its recovery was independent of soil properties. The E-to-FB ratio and percent recovery of mycelial ergosterol helped establish for the first time relationships determining soil FB and FB-C from soil ergosterol concentration. The amount of FB ranged from 155 to 4745 microgram g-1 and that for FB-C ranged from 67 to 2040 microgram g-1 for different soils, and was higher in samples taken from native undisturbed land than in samples taken from adjacent cultivated fields. Measurement of soil ergosterol concentration is a useful estimate content of the living soil FB.

The seasonal responses of soil microbial biomass C to change in atmospheric temperature, soil moisture and soluble organic C were studied in soils from the karst areas of southwest China. These soils are relatively weathered, leached and impoverished, and have a low input of plant residues. Over 1 year, an inverse relationship between soil microbial biomass C and atmospheric temperature was found. The highest microbial biomass C occurred in winter and the lowest in summer, and ranged from 231-723 micrograms g-1 dry soil. Although there was no obvious relationship between microbial biomass C and soil moisture, a negative correlation existed between microbial biomass C and soluble organic C. In the ecosystem studied, the marked changes in soil microbial biomass C at above 20 degrees C were ascribed to fluctuations of soil moisture, which were controlled by climatic factors and geomorphic conditions. The patterns of soluble organic C turnover were similar to those of soluble carbohydrate C, both of which were controlled by soil drying-rewetting cycles. It was concluded that the lowest amounts of soil microbial biomass C, measured in the summer, resulted in increases in soluble organic C due to higher turnover rates of the former at warmer air temperatures. Thus, there was a marked seasonal change in soil microbial biomass C.

Two soils from temperate sites (UK; arable and grassland) were incubated aerobically at 0, 5, 15 or 25 degrees C for up to 23 days. During this period both soils were analysed for soil microbial biomass carbon (biomass C) and adenosine 5' triphosphate contents (ATP). Biomass C did not change significantly in either soil at any temperature throughout, except during days 0 to 1 in the grassland soil. Soil ATP contents increased slowly throughout the 23 days of incubation, from 2.2 to a maximum of 3.1 nmol ATP g-1 soil in the arable soil (a 40% increase) and from 6.2 to a maximum of 11.2 nmol ATP g-1 soil in the grassland soil (an increase of 81%), both at 25 degrees C. Since biomass C did not change either with increasing temperature or increasing time of incubation, it was concluded that an increase in ATP was either due to an increase in adenylate energy charge or de novo synthesis of ATP, or both. During the incubation, biomass ATP concentrations ranged from about 5 to 12 micromol ATP g-1 biomass C but trends between biomass ATP and incubation temperatures were not very obvious until about day 13. On day 23, biomass ATP concentrations were positively and linearly related to temperature: (micromol ATP g-1 biomass C = 6.98 +/- 0.35 + 0.134 +/- 0.023 T0 (r2 = 0.77) with no significant difference in the slope between the grassland and arable soils. At 25 degrees C the biomass ATP concentration was 10.3 micromol g-1 biomass C, remarkably close to many other published values. It was concluded that, although the biomass increased its ATP concentration in response to increasing temperature, the increase was comparatively small. Also, at all temperatures tested, the biomass maintained its ATP concentration within the range commonly reported for micro-organisms growing expontentially in vitro. This is despite the fact that the biomass normally exhibits other features more typical of a "resting" or dormant population--a paradox which still is not resolved.

Two key questions regarding the effects of elevated atmospheric CO2 on soil microbial biomass are, (a) will future levels of elevated CO2 affect the amount of microbial biomass in soil? and (b) how will any observed changes impact on C-flux from soils? These questions were addressed by examining soil microbial biomass, and in situ estimations of soil respiration in grassland soils exposed to free air carbon dioxide enrichment (60 Pa). Corresponding measurements of plant litter mass loss were taken using litter bags, ensuring that ambient litter was decomposed in ambient soil, and elevated CO2 grown litter was decomposed in soils exposed to elevated CO2. Significantly greater levels of microbial biomass (p < 0.05, paired t-test) were detected in soils exposed to elevated CO2 (1174.1 compared to 878.9 microgram N g-1 dry soil for ambient CO2 exposed soils). This corresponded with a significant increase (p < 0.005, paired t-test) in situ soil respiration from the elevated CO2 acclimatised soils (28.7 compared to 20.4 micromol CO2 m2 h-1 from soils exposed to ambient CO2). However, when soil respiration was calculated per unit of microbial biomass, no differences in activity per unit biomass were detected (approx. 0.02 micromol CO2 m2 h-1 unit biomass-1), suggesting that increased soil microbial biomass, rather than increased activity was responsible for the observed differences. The mass loss of litter was greater in the elevated CO2 acclimatised soils (p < 0.05, ANOVA), even though the initial nutrient ratios of the litter were not significantly different.

The present research was conducted to determine the relationship between the degradation of rim-sulfuron and soil microbial biomass C in a laboratory-incubated clay loam soil (pH=8.1; organic matter = 2.1%) under different conditions and at different initial dosages (field rate, 10 and 100 times the field rate). The half-life values varied between 0.4 and 103.4 days depending on temperature, soil moisture and initial dose. Evidence suggested that rimsulfuron could pose environmental risks in cold and dry climatic conditions. Significant decreases in microbial biomass C content in rimsulfuron-treated soil, compared to untreated soil, were observed initially, especially at higher temperatures and low moisture levels, but never exceeded 20.3% of that in control soil. The microbial biomass C content then returned to initial values at varying times depending on incubation conditions. The relationship between herbicide degradation and microbial biomass C content gave parabolic curves (P < 0.005 in all cases) under all conditions tested. Generally, maximum biomass C decrease coincided with the decrease in the concentration of rimsulfuron to about 50% of the initial dose, except at 10 degrees C and 100 x, when biomass began to recover as early as 65-70% of the initial dose. The final equations could be useful to deduce the decrease of soil microbial biomass in relation to herbicide concentration. From the degradation kinetics of the herbicide, the time required to reach this decrease can also be calculated.

The research investigated the impact of the yellow lupin biomass undergoing decomposition in soil on the emergence and initial growth of seedlings of winter wheat and spring barley, depending on the dose and the method of biomass introduction into the topsoil. The laboratory experiment was carried out in the vegetation lab of the Dept. of Land and Plant Cultivation of the Bydgoszcz University of Technology and Agriculture from 1997 to 99. The experiment factors included yellow lupin biomass dose, the method of biomass introduction, namely onto the soil surface, into at the depth of 4 cm, biomass mixed with soil up to the depth of 5 cm, biomass mixed with a soil layer at the depth of 5-10 cm. The results suggest that the impact of yellow lupin biomass undergoing decomposition on the emegrence and initial growth of winter wheat and spring barley depended both on its dose and the method of its introduction into the topsoil. The yellow lupin biomass introduced into soil at the seed sowing depth inhibited the emergence significantly in both cereal species; the higher the dose, the greater the inhibition

Microbial biomass growth, S mineralization after compost amendment (plant seeding) and S uptake by African millet at d 30, 60 and 120 (first, second, and third cutting, respectively) were monitored in an S-deficient soil amended with cattle manure compost (CMC), saw dust compost (SDC) or rice husk compost (RHC) at the rate of 20 t ha-1 in the presence or absence of growing African millet. A chemical fertilizer (CF) treatment at the rate of 30 microgram g-1 soil along with a control (CT) was included for comparison. CMC produced a significantly larger microbial biomass-C and -S than SDC or RHC. In the planted soil, during rapid growth of African millet, microbial biomass-S decreased more rapidly than in unplanted soil. Both biomass-C and biomass-S then showed a significant flush particularly at d 60-120 in all the treatments. CMC, RHC and SDC released 20, 10, and 8 microgram CaCl2 extractable S g-1 soil, respectively, by d 5. Microbial biomass showed a marked increase in C-to-S ratio across the treatments which eventually reached 154 in the unplanted soil and 291 in the planted soil from an initial value of 64. Substantial mineralization of soil organic-S in all the treatments was observed during the period of greatest plant growth, but not in the absence of plants. Total S uptake was 37, 81 and 76% lower in the CMC, SDC and RHC amendment, respectively, than that of CF. CMC improved the S supplying potential of the soil, but addition of SDC or RHC (high C-to-S ratio) resulted in severe S deficiency of plant due to S immobilization in soil.

The aim of the model experiment was to verify the hypothesis that soil indicator of oxygenation status, can be used to define plant response in terms of biomass productivity. It was found that biomass production for the two cultivars was differentiated by soil oxygenation

The wide utilization of copper in agriculture and industrial processes in addition to many other uses associated with human activities causes both point and non-point source pollution of the environment with copper. Although copper is relatively non-toxic to mammals and essential micronutrient necessary for a wide variety of prokaryotic and eukaryotic metabolic activities, is toxic to all organisms if present in elevated concentrations. Copper pollution in agricultural posing soils can adversely affect the living part of soil organic matter serious threat to sustained food and fiber production.

This study examines the effect of soil P status and N addition on the decomposition of 14C-labelled glucose to assess the consequences of reduced fertilizer inputs on the functioning of pastoral systems. A contrast in soil P fertility was obtained by selecting two hill pasture soils with different fertilizer history. At the two selected sites, representing low (LF) and high (HF) fertility status, total P concentrations were 640 and 820 mg kg-1 and annual pasture production was 4,868 and 14,120 kg DM ha-1 respectively. Soils were amended with 14C-labelled glucose (2,076 mg C kg-1 soil), with and without the addition of N (207 mg kg-1 soil), and incubated for 168 days. During incubation, the amounts of 14CO2 respired, microbial biomass C and 14C, microbial biomass P, extractable inorganic P (Pi) and net N mineralization were determined periodically. Carbon turnover was greatly influenced by nutrient P availability. The amount of glucose-derived 14CO2 production was high (72%) in the HF and low (67%) in the LF soil, as were microbial biomass C and P concentrations. The 14C that remained in the microbial biomass at the end of the 6-month incubation was higher in the LF soil (15%) than in the HF soil (11%). Fluctuations in Pi in the LF soil during incubation were small compared with those in HF soil, suggesting that P was cycling through microbial biomass. The concentrations of Pi were significantly greater in the HF samples throughout the incubation than in the LF samples. Net N mineralization and nitrification rates were also low in the LF soils, indicating a slow turnover of microorganisms under limited nutrient supply. Addition of N had little effect on biomass 14C and glucose utilization. This suggests that, at limiting P fertility, C turnover is retarded because microbial biomass becomes less efficient in the utilization of substrates.