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Abstract: This field study was initiated to measure soil CO2 evolution of the Turiel ridge tillage system under faba bean (Vicia faba L.) compared with mouldboard ploughing. The CO2–C measurements were done in situ with a transportable infrared gas analyzer at different positions on the ridges and furrows and on mouldboard plough plots with and without vegetation, respectively. The CO2 evolution at different ridge positions reflected a ridge pattern with a CO2–C evolution in the order crown>shoulder>furrow. On a hectare basis the mouldboard ploughed soil evolved 0.11t more CO2–Cha−1 than ridges, and the plots with vegetation evolved 0.58t more CO2–Cha−1 than the plots without vegetation during the investigation period of 57 days. At higher air temperatures the soil temperature tended to be higher on ploughed plots compared to ridges. The CO2 evolution on the planted plots decreased with time, reflecting the decreasing physiological activity of the plant roots. Overall, despite a high degree of soil disturbance, the amount of CO2 evolved from the ridge tilled soil was lower compared to mouldboard plough tillage, probably reflecting less favorable conditions for soil microorganisms in the ridges compared to the ploughed soil. [Copyright &y& Elsevier]

Abstract: The present study was conducted to determine the spatial heterogeneity of bulk density, soil moisture, inorganic N, microbial biomass C, and microbial biomass N in the ridge tillage system of Turiel compared to conventional mouldboard ploughing on three sampling dates in May, July, and August. The soil sampling was carried out under vegetation representing the ridge in a high spatial resolution down the soil profile. Bulk density increased with depth and ranged from 1.3gcm−3 at 10cm depth to 1.6gcm−3 at 35cm in ploughed plots and from 1.0gm−3 at 5cm to 1.4gm−3 at 35cm in the ridges. In the ploughed plots, the contents of microbial biomass C and microbial biomass N remained roughly constant at 215 and 33μgg−1 soil, respectively, throughout the experimental period. The microbial biomass C/N ratio varied in a small range around 6.4. In the ridged plots, the contents of microbial biomass C and microbial biomass N were 5% and 6% higher compared to the ploughed plots. Highest microbial biomass C contents of roughly 300μgg−1 soil were always measured in the crowns in July. The lowest contents of microbial biomass C of 85–137μgg−1 soil were measured in the furrows. The ridges showed strong spatial heterogeneity in bulk density, soil water content, inorganic nitrogen and microbial biomass. [Copyright &y& Elsevier]

Abstract: The objective of this study was to investigate the effects of biogas slurry derived from straw-rich farmyard manure on the soil microbial biomass, on the mineralization in the field and on the related crop yield. The experiment was carried out in the following four treatments: (1) fallow, (2) fallow+biogas slurry, (3) spring barley, and (4) spring barley+biogas slurry. The CO2 evolution rate ranged between 15 and 120mgCm−2 h−1 in both fallow treatments and showed a significant exponential relationship with the soil temperature at 5cm depth. According to the extrapolation of the CO2 evolution rates into amounts per hectare, approximately 200kgCha−1 or 27% of the biogas slurry derived C were mineralized to CO2 during a 50 days’ period to 18 June in the fallow treatment with biogas slurry. An additional amount of up to 29.5kg inorganic Nha−1 could be calculated as the sum of NH4-N already present in biogas slurry at the time of amendment and from the amount of biogas slurry mineralized in the soil to NO3-N. A good agreement between measured and modelled stocks of inorganic N at 0–60cm depth was obtained after having five-fold increased soil organic C turnover compared to the default values of the model DNDC. The mineralization data are in line with an amount of up to 21kgha−1 more N transferred by the barley plants to their aboveground biomass in biogas slurry treatment. The N not accounted for by the aboveground plant biomass could be explained by the belowground plant-derived N. CO2 evolution from the soil surface, inorganic N content at 0–60cm depth and N transfer into barley aboveground biomass lead apparently to similar results after the application of biogas slurry. The soil ATP content after harvest of the barley was significantly larger in the two treatments with biogas slurry, especially in the fallow treatment indicating a positive effect on the soil microbial community. [Copyright &y& Elsevier]

Abstract: Goals of ecosystem restoration in California grasslands include the reestablishment of plant communities with a high proportion of native species, and simultaneously improve soil nutrient cycling. Addition of annual lupines and a litter mulch layer were hypothesized to be factors that would promote the growth of the native perennial bunchgrass, Nassella pulchra, in a restored California grassland. To test this hypothesis, field mesocosms were installed, each encircling a Nassella plant, at a perennial grassland restoration site in Carmel Valley, California. Two sets of treatments were imposed: (1) seeding of the annual N-fixing legume, Lupinus bicolor; and (2) exchanging the grassland litter for a thicker mulch layer of C4 grass litter (C/N=99). Stable isotope analysis allowed the tracking of fates of N fixed by the legume and the C4-litter derived C. Treatments continued for 28 months, from December 2002 to April 2005, when most of the destructive measurements were taken. In 2005, neither treatment had significantly increased the biomass of the annuals or the perennial bunchgrass, and there was little effect on total soil C and N. Lupinus decreased the δ15N content, but did not affect the biomass, N and P content of the litter, which was largely composed of annual plants from the previous year. Lupinus resulted in higher soil microbial biomass carbon (SMB-C), and distinct effects on soil microbial communities, especially soil fungi, as measured by phospholipid fatty acid analysis (PLFA) and ergosterol. The high C/N litter mulch tended to increase biomass of Nassella, despite its lower P concentration, and it reduced SMB-C, presumably due to lower decomposition rates compared to the ambient litter. Using a high C/N litter mulch thus is ambiguous for grassland restoration. Repeated increases of legumes over a longer time frame may potentially increase soil fertility and soil C pools in California grasslands, but this study suggests that native perennial grasses may be slow to benefit. [Copyright &y& Elsevier]

Abstract: An incubation experiment was carried out to investigate whether salinity at high pH has negative effects on microbial substrate use, i.e. the mineralization of the amendment to CO2 and inorganic N and the incorporation of amendment C into microbial biomass C. In order to exploit natural differences in the 13C/12C ratio, substrate from two C4 plants, i.e. highly decomposed and N-rich sugarcane filter cake and less decomposed N-poor maize leaf straw, were added to two alkaline Pakistani soils differing in salinity, which had previously been cultivated with C3 plants. In soil 1, the additional CO2 evolution was equivalent to 65% of the added amount in the maize straw treatment and to 35% in the filter cake treatment. In the more saline soil 2, the respective figures were 56% and 32%. The maize straw amendment led to an identical immobilization of approximately 48μgNg−1 soil over the 56-day incubation in both soils compared with the control soils. In the filter cake treatment, the amount of inorganic N immobilized was 8.5μgNg−1 higher in soil 1 than in soil 2 compared with the control soils. In the control treatment, the content of microbial biomass C3-C in soil 1 was twice that in soil 2 throughout the incubation. This fraction declined by about 30% during the incubation in both soils. The two amendments replaced initially similar absolute amounts of the autochthonous microbial biomass C, i.e. 50% of the original microbial biomass C in soil 1 and almost 90% in soil 2. The highest contents of microbial biomass C4-C were equivalent to 7% (filter cake) and 11% (maize straw) of the added C. In soil 2, the corresponding values were 14% lower. Increasing salinity had no direct negative effects on microbial substrate use in the present two soils. Consequently, the differences in soil microbial biomass contents are most likely caused indirectly by salinity-induced reduction in plant growth rather than directly by negative effects of salinity on soil microorganisms. [Copyright &y& Elsevier]

Abstract: A 49-day incubation experiment was carried out with the addition of field-grown maize stem and leaf residues to soil at three different temperatures (5, 15, and 25°C). The aim was to study the effects of two transgenic Bt-maize varieties in comparison to their two parental non-Bt varieties on the mineralization of the residues, on their incorporation into the microbial biomass and on changes in the microbial community structure. The stem and leaf residues of Novelis-Bt contained 3.9μgg−1 dry weight of the Bt toxin Cry1Ab and those of Valmont-Bt only 0.8μgg−1. The residues of the two parental non-Bt varieties Nobilis and Prelude contained higher concentrations of ergosterol (+220%) and glucosamine (+190%) and had a larger fungal C-to-bacterial C ratio (+240%) than the two Bt varieties. After adding the Bt residues, an initial peak in respiration of an extra 700μgCO2–Cg−1 soil or 4% of the added amount was observed in comparison to the two non-Bt varieties at all three temperatures. On average of the four varieties, 19–38% of the maize C added was mineralized during the 49-day incubation at the three different temperatures. The overall mean increase in total maize-derived CO2 evolution corresponded to a Q 10 value of 1.4 for both temperature steps, i.e. from 5 to 15°C and from 15 to 25°C. The addition of maize residues led to a strong increase in all microbial properties analyzed. The highest contents were always measured at 5°C and the lowest at 25°C. The variety-specific contents of microbial biomass C, biomass N, ATP and adenylates increased in the order Novelis-Bt ⩽ Prelude

Abstract: A 20-day incubation experiment with continuous cereal (CC) versus cereal legume (CL) rotation soils of two semi-arid Sub-Saharan sites (Fada-Kouaré in Burkina Faso, F, and Koukombo in Togo, K) were carried out to investigate the effects of rewetting on soil microbial properties. Site- and system-specific reactions of soil microorganisms were observed on cumulative CO2 production, adenylates (ATP, ADP, and AMP), microbial biomass C and N, ergosterol, muramic acid and glucosamine. Higher values of all parameters were found in the CL rotation soils and in both soils from Fada-Kouaré. While the inorganic N concentration showed only a system-specific response to rewetting, the adenylate energy charge (AEC) showed only a site-specific response. ATP recovered within 6h after rewetting from ADP and AMP due to rehydration of microorganisms and not due to microbial growth. Consequently, no N seemed to be immobilized by microorganisms and all NO3 in the soil was immediately available to the plants. The fungal cell-membrane component ergosterol was three (CC) and five (CL) times larger at Fada than in the respective soils at Koukombo. The concentrations of the bacterial cell-wall component muramic acid were by 20% and of mainly fungal glucosamine by 10% larger in the CL rotation soils than in the CC soils. This indicates long-shifts in the microbial community structure. [Copyright &y& Elsevier]

Abstract: Agricultural practices have strong impacts on soil microbes including both the indices related to biomass and activity as well as those related to community composition. In a grassland restoration project in California, where native perennial bunchgrasses were introduced into non-native annual grassland after a period of intensive tillage, weeding, and herbicide use to reduce the annual seed bank, microbial community composition was investigated. Three treatments were compared: annual grassland, bare soil fallow, and restored perennial grassland. Soil profiles down to 80cm in depth were investigated in four separate layers (0–15, 15–30, 30–60, and 60–80cm) using both phospholipid ester-linked fatty acid (PLFAs) and ergosterol as biomarkers in addition to microbial biomass C by fumigation extraction. PLFA fingerprinting showed much stronger differences between the tilled bare fallow treatment vs. grasslands, compared to fewer differences between restored perennial grassland and annual grassland. The presence or absence of plants over several years clearly distinguished microbial communities. Microbial communities in lower soil layers were little affected by management practices. Regardless of treatment, soil depth caused a strong gradient of changing habitat conditions, which was reflected in Canonical Correspondence Analysis of PLFAs. Fungal organisms were associated with the presence of plants and/or litter since the total amount and the relative proportion of fungal markers were reduced in the tilled bare fallow and in lower layers of the grassland treatments. Total PLFA and soil microbial biomass were highly correlated, and fungal PLFA biomarkers showed strong correlations to ergosterol content. In conclusion, microbial communities are resilient to the grassland restoration process, but do not reflect the change in plant species composition that occurred after planting native bunchgrasses. [Copyright &y& Elsevier]

Abstract: A laboratory experiment was carried out to prove the hypothesis that the decomposition of a complex organic substrate is reduced by the lower content of fungal biomass in a saline soil in comparison to a non-saline soil under acidic conditions. Three different rates (0.5, 1.0, and 2.0%) of sugarcane filter cake were added to both soils and incubated for 63 days at 30°C. In the saline control soil without amendment, cumulative CO2 production was 70% greater than in the corresponding non-saline control soil, but the formation of inorganic N did not differ between these two soils. However, nitrification was inhibited in the saline soil. The increase in cumulative CO2 production by adding filter cake was similar in both soils, corresponding to 29% of the filter cake C at all three addition rates. Also, the increases in microbial biomass C and biomass N were linearly related to the amount of filter cake added, but this increase was slightly higher for both properties in the saline soil. In contrast to microbial biomass, the absolute increase in ergosterol content in the saline soil was on average only half of that in the non-saline soil and it also showed strong temporal changes during the incubation: a strong initial increase after adding the filter cake was followed by a rapid decline. The addition of filter cake led to immobilisation of inorganic N in both soils. This immobilisation was not expected, because the total C-to-total N ratio of the filter cake was below 13 and the organic C-to-organic N ratio in the 0.5M K2SO4 extract of this material was even lower at 9.2. The immobilisation was considerably higher in the saline soil than in the non-saline soil. The N immobilisation capacity of sugarcane filter cake should be considered when this material is applied to arable sites at high rations. [Copyright &y& Elsevier]

Abstract: An incubation experiment was carried out with maize (Zea mays L.) leaf straw to analyze the effects of mixing the residues with soil and N amendment on the decomposition process. In order to distinguish between soil effects and nitrogen effects for both the phyllospheric microorganisms already present on the surface of maize straw and soil microorganisms the N amendment was applied in two different placements: directly to the straw or to the soil. The experiment was performed in dynamic, automated microcosms for 22 days at 15°C with 7 treatments: (1) untreated soil, (2) non-amended maize leaf straw without soil, (3) N amended maize leaf straw without soil, (4) soil mixed with maize leaf straw, (5) N amended soil, (6) N amended soil mixed with maize leaf straw, and (7) soil mixed with N amended maize leaf straw. 15NH4 15NO3 (5at%) was added. Gas emissions (CO2, 13CO2 and N2O) were continuously recorded throughout the experiment. Microbial biomass C, biomass N, ergosterol, δ13C of soil organic C and of microbial biomass C as well as 15N in soil total N, mineral N and microbial biomass N were determined in soil samples at the end of the incubation. The CO2 evolution rate showed a lag-phase of two days in the non-amended maize leaf straw treatment without soil, which was completely eliminated when mineral N was added. The addition of N generally increased the CO2 evolution rate during the initial stages of maize leaf straw decomposition, but not the cumulative CO2 production. The presence of soil caused roughly a 50% increase in cumulative CO2 production within 22 days in the maize straw treatments due to a slower decrease of CO2 evolution after the initial activity peak. Since there are no limitations of water or N, we suggest that soil provides a microbial community ensuring an effective succession of straw decomposing microorganisms. In the treatments where maize and soil was mixed, 75% of microbial biomass C was derived from maize. We concluded that this high contribution of maize using microbiota indicates a strong influence of organisms of phyllospheric origin to the microbial community in the soil after plant residues enter the soil. [Copyright &y& Elsevier]

For millennia oasis agriculture has been the backbone of rural livelihood in the desertic Sultanate of Oman. However, little is known about the functioning of these oasis systems, in particular with respect to the C turnover. The objective was to determine the effects of crop, i.e. alfalfa, wheat and bare fallow on the CO2 evolution rate during an irrigation cycle in relation to changes in soil water content and soil temperature. The gravimetric soil water content decreased from initially 24% to approximately 16% within 7 days after irrigation. The mean CO2 evolution rates increased significantly in the order fallow (27.4 mg C m−2 h−1) < wheat (45.5 mg C m−2 h−1) < alfalfa (97.5 mg C m−2 h−1). It can be calculated from these data that the CO2 evolution rate of the alfalfa root system was nearly four times higher than the corresponding rate in the wheat root system. The decline in CO2 evolution rate, especially during the first 4 days after irrigation, was significantly related to the decline in the gravimetric water content, with r=0.70. CO2 evolution rate and soil temperature at 5 cm depth were negatively correlated (r=−0.56, n=261) due to increasing soil temperature with decreasing gravimetric water content. [Copyright &y& Elsevier]

The aim of our research was to study how a gradient in salinity under low pH conditions affected activity, community structure, and biomass of soil microorganisms. The study was conducted near Heringen, Germany, at five sites in the floodplain of the river Werra, which were affected by saline liquid residues from potassium mining injected into the underground geological formations. The content of soluble salts ranged from 2.1 at site 1 to 9.7 mg g−1 soil at site 5. Soil pH ranged from 3.85 to 4.55. Microbial biomass C, biomass N, fungal ergosterol and adenosine triphosphate (ATP) were highly significantly interrelated with correlation coefficients between r=0.89 and 0.96 (P<0.0001, n=25). All soil biological properties except adenosine monophosphate had highest values at the low saline site 1 and lowest at the most acidic and most saline site 5. The strongest decrease with salinity was shown by ATP and ergosterol, achieving only 12 and 4% of the site 1 values, respectively. The ATP-to-microbial biomass C ratio declined to 46% of the maximum level at site 1, the microbial biomass C-to-soil organic C ratio to 38%, and the ergosterol-to-microbial biomass C ratio to 19%. All microbial indices, except basal respiration, exhibited strong salinity effects due to shifts in the microbial community structure towards prokaryotic microorganisms. Consequently, salinity is one of the most stressing environmental conditions for soil microorganisms. [Copyright &y& Elsevier]

The determination of the isotopic composition of the microbial biomass C in soil is an important tool to study soil microbial ecology and the decomposition and microbial immobilization of soil organic C. We discuss advantages and disadvantages of different methods to determine 13C/12C in soil microbial biomass and propose a new procedure that is based on the UV-catalyzed liquid oxidation of fumigated and non-fumigated soil extracts combined with trapping of the released CO2 in liquid nitrogen and subsequent determination of δ13O2-C by a gas chromatograph connected with an isotope ratio mass spectrometer (IRMS). This method was evaluated using test solutions with known isotopic composition and soil extracts. Additionally, the method was compared with an off-line sample preparation technique combined with isotope analysis by a dual-inlet IRMS and an on-line analysis using an elemental analyser connected with an IRMS. All methods applied obtained comparable results and there were no significant differences between the δ13Cvalues measured. The off-line preparation procedure had the highest precision but it was also the most labour-intensive. The choice of the most suitable method depends mainly on the number of samples that have to be analysed, the salt concentration of the extracts and the differences of δ13Cthat have to be detected. The application of this method with liquid oxidation and subsequent GC-IRMS analysis showed that microbial biomass C of a grassland soil was 13C-enriched by 2‰δ13CPDBcompared with the total soil organic C. The addition of maize straw resulted in a rapid immobilization of maize C in the microbial biomass. [Copyright &y& Elsevier]

[Display omitted] • Consideration of soil microbial biomass elements beyond C, N, and P. • Structural and physiological functions of elements in soil bacteria, archaea, and fungi. • Functions of elements in the context of soil ecosystem services. The soil microbial community fulfils various functions, such as nutrient cycling and carbon (C) sequestration, therefore contributing to maintenance of soil fertility and mitigation of global warming. In this context, a major focus of research has been on C, nitrogen (N) and phosphorus (P) cycling. However, from aquatic and other environments, it is well known that other elements beyond C, N, and P are essential for microbial functioning. Nonetheless, for soil microorganisms this knowledge has not yet been synthesised. To gain a better mechanistic understanding of microbial processes in soil systems, we aimed at summarising the current knowledge on the function of a range of essential or beneficial elements, which may affect the efficiency of microbial processes in soil. This knowledge is discussed in the context of microbial driven nutrient and C cycling. Our findings may support future investigations and data evaluation, where other elements than C, N, and P affect microbial processes. [ABSTRACT FROM AUTHOR]

Soil microorganisms require a range of essential elements for their optimal functioning and store several elements in the microbial biomass (MB), such as carbon (C), nitrogen (N), phosphorus (P) and sulphur (S), as well as other secondary and trace elements. The C, N and P content of the microbial biomass has been quantified in many studies for many years, whereas S has been the focus only in a few studies, despite the availability of methods and the relevance of MBS for the S turnover in soils. To illustrate the relevance of MBS, this review aims at summarizing the current state of knowledge on the quantities of MBS in different soils, influencing environmental and agricultural management factors, methodological shortcomings, and prospects for soil microbial biomass research. Median MBS contents were 6.0 µg g−1 soil in arable, 7.6 µg g−1 soil in grassland, and 5.7 µg g−1 soil in forest soils. All extractants used led to similar MBS contents in soils with similar soil organic (SO) C contents. MBC and soil pH positively explained MBS, using multiple linear regression analysis. Median MB-C/S ratios increased in the order arable (55), grassland (85), and forest (135) soils. As the overall quantity of MBS data is still small, future studies are required to verify these observations. Moreover, future research needs to more strongly consider stoichiometric relationships of elements in the soil and the soil microbial ionome. The role of S and its complex relationship with the availability of other elements in soils for the soil microbial biomass and its functions remains to be elucidated. [ABSTRACT FROM AUTHOR]

Predicted increase in climate warming will affect soil organic carbon (SOC) dynamics in vulnerable cold alpine environments. In contrast to freeze and thaw cycles, less is known about the effects of temperature regimes in the range between 2 and 10 °C on SOC availability to soil microorganisms. For this reason, CO 2 efflux, extracellular enzyme activities and microbial communities were measured in an incubation experiment with three temperature treatments: (T1) continuous 10 °C, (T2) cooled down to 2 °C, and (T3) rewarmed from 2 to 10 °C. Two forest soils at low elevation and two grassland soils at high elevation were taken from two sites with distinct bedrock types (limestone at Hochschwab, gneiss and schist at Rauris). The CO 2 efflux did not differ significantly between the elevation levels at the two sites. In the continuous warm treatment T1, the relative decline in CO 2 efflux was stronger in the two Rauris than in the two Hochschwab soils during the 0–123 days period. In the cooling treatment T2, the cumulative ΣCO 2 C efflux of the Hochschwab soils was lowered by 32% and that of the Rauris soils by only 19% compared with T1 during the 30–123 days period. In the rewarming treatment T3, the ΣCO 2 efflux was on average 33% higher than that of treatment T1 during the 91–123 days period, ranging from +8% to +62%. Phospholipid fatty acid (PLFA) composition and extracellular enzyme activities were not markedly affected by incubation time or temperature treatments. The differences in bedrock properties had stronger effects on the ΣCO 2 efflux, enzyme activities as well as total PLFA content and composition than elevation level or vegetation. Other, largely unknown factors control the rewarming effects on the mobilisation of a labile SOC pool. • The CO 2 efflux declined more rapidly in the Rauris than in the Hochschwab soils at 10 °C. • This was caused by the lower contribution of easily decomposable plant residues at Rauris. • Rewarming from 2 to 10 °C, increased the cumulative CO 2 efflux in all soils. • A rewarming-induced priming effect occurred in the Rauris low elevation forest soil. • PLFA composition and enzyme activities did not reflect the temperature regime effects. [ABSTRACT FROM AUTHOR]

• Contribution of microbial necromass C to SOC was lower at Hochschwab (alkaline site) than at Rauris (acidic site). • Hochschwab was dominated by hydrolytic, while Rauris by oxidative enzymes activities. • Fungal biomass and necromass dominated at both sites, especially stronger at Hochschwab. • G + bacteria dominated bacterial PLFAs at both sites, especially stronger at Rauris. • Microbial biomass and necromass accumulation strategies vary with soil mineralogy. Microbial necromass is an important part of soil organic carbon (SOC), but the changes in its contribution along elevational gradients and soil types are poorly understood. At two sites, the alkaline site Hochschwab and the acidic site Rauris, soil samples from three elevation levels and depths were analysed for amino sugars as microbial necromass indices, extracellular enzymes, and phospholipid fatty acids (PLFA) as microbial biomass indices. The three elevation levels at each site represented similar temperature and precipitation regimes. Microbial necromass contribution to SOC was lower (26%) at the alkaline site than at the acidic site (37%), indicating lower transformation of microbial biomass into stable SOC and support the increased accumulation of fungal necromass under N limitation at Hochschwab. Fungi generally dominate microbial necromass, with 88% at Hochschwab and 77% at Rauris. At the alkaline site Hochschwab, phenoloxidase, peroxidase and phosphatase enzymes activities were lower by 96%, 98% and 75%, respectively than at the acidic Rauris site, but not those of the hydrolytic enzymes β-glucosidase, exo-glucanase, exo-chitinase, and protease, indicating retarded decomposition of plant residues. Gram positive bacteria dominate bacterial biomass at both sites, with 70% at Hochschwab and 72% at Rauris. The higher fungal to bacterial PLFA ratio suggest increased contribution of fungi to total microbial PLFA at Hochschwab due to the better adaptability of fungi to the site-specific environmental conditions. Effects along alpine elevation gradients depend on vegetation induced changes in soil properties, which interact with bedrock properties. [ABSTRACT FROM AUTHOR]

Effects of soil type and microclimate on winter decomposition of maize (Z ea mays L) leaf litter and microbial carbon use efficiency (CUE) were investigated, using a reciprocal soil transplantation experiment. The clay site DEP is located at an elevated plateau on limestone, the silt site NEB at a broad valley on loess. At DEP, the mean soil temperature was 0.4 °C higher than at NEB. Mean CO 2 efflux was 62.8 g C m−2 130 d−1 at NEB, more than 4 times higher than that of 15.1 g C m−2 130 d−1 at DEP. At both sites, no differences in CO 2 efflux were observed between soil type and maize leaf litter treatments. The alkaline clay and the calcareous bedrock at DEP apparently trapped all CO 2 evolved below 4 cm depth. Microbial biomass C (MBC) content was about 50% lower in the silt than in the clay at 0–4 cm depth. The ergosterol to MBC ratio was 13% higher in the clay than in the silt. Maize leaf litter application increased MBC as well as the MB-C/N ratio from 7.9 to 9.7 but decreased the ergosterol to MBC ratio by 9%. Total recovery of maize leaf litter C was 65%, i.e. the sum of MBC (10%), microbial residue C (32%) and particulate organic matter C (23%), while the remaining 35% must have been lost as CO 2. From these data, a CUE of 0.55 was calculated for maize leaf litter in the field, which was not affected by soil type and site conditions. • The silt contained about 50% less microbial biomass than the clay. • Soil type and maize leaf litter amendment did not affect CO 2 efflux. • A C use efficiency of 0.55 was calculated for maize leaf litter in the field. [ABSTRACT FROM AUTHOR]

Abstract: Chisel plough or no-till practises are clearly attributed to sustainable farming for the support of soil organisms and soil biological functioning. However, in organic farming these techniques are only applied to a very small extent since there is a need for cultivation to control weeds. In organic farming it is important to develop and establish less destructive soil tillage practises to benefit from the support of soil organisms, especially from ecosystem engineers like earthworms. In this study three tillage systems were compared on a silty, loess'' derived soil in a 6 crop rotation. The tillage systems established were: (1) “ecomat” shallow (10cm) inversive ploughing; (2) a ridge culture system; and (3) conventional tillage (inversion tillage) down to 30cm. In fall 2005, three years after establishment of the field plots earthworm communities were investigated using formalin extraction. In total 6 species were detected. The earthworm abundance was low, ranging from 0 to 84 individuals m−2. Shallow ploughing using the “ecomat” technique was not different than conventional ploughing in its effects on earthworm populations, while the ridge culture system was significantly reduced in earthworm numbers and biomass compared to conventional ploughing. We conclude that both “ecomat” and “ridge culture” do not support earthworms and significantly reduce earthworm densities. The reductions in tillage depth alone are not effective for improving the habitat quality for earthworms in soil. [Copyright &y& Elsevier]

Extracellular polymeric substances (EPS) are produced by microorganisms and interact to form a complex matrix called biofilm. In soils, EPS are important contributors to the microbial necromass and, thus, to soil organic carbon (SOC). Amino sugars (AS) are used as indicators for microbial necromass in soil, although the origin of galactosamine and mannosamine is largely unknown. However, indications exist that they are part of EPS. In this study, two bacteria and two fungi were grown in starch medium either with or without a quartz matrix to induce EPS production. Each culture was separated in two fractions: one that directly underwent AS extraction (containing AS from both biomass and EPS), and another that first had EPS extracted, followed then by AS determination (exclusively containing AS from EPS). We did not observe a general effect of the quartz matrix neither of microbial type on AS production. The quantified amounts of galactosamine and mannosamine in the EPS fraction represented on average 100% of the total amounts of these two AS quantified in cell cultures, revealing they are integral parts of the biofilm. In contrast, muramic acid and glucosamine were also quantified in the EPS, but with much lower contribution rates to total AS production, of 18% and 33%, respectively, indicating they are not necessarily part of EPS. Our results allow a meaningful ecological interpretation of mannosamine and galactosamine data in the future as indicators of microbial EPS, and also attract interest of future studies to investigate the role of EPS to SOC and its dynamics., Competing Interests: The authors declare no competing interests., (© The Author(s) 2024. Published by Oxford University Press on behalf of the International Society for Microbial Ecology.)

Conservation tillage is often discussed as an effective tool to improve the soil quality in agriculture. Four sites across Europe (in Germany, Romania, Spain, and Sweden) were investigated as case studies for country-specific reductions in tillage intensity. Conventional tillage (CT) by mouldboard ploughing was compared with shallow and deep non-inversion minimum tillage (MT) and/or no-tillage (NT). In Sweden, NT and MT had positive effects on the concentrations of soil organic carbon (SOC), total nitrogen (N), and microbial biomass carbon (MBC) in the upper 20 cm compared with CT. At the German site, MT increased SOC, N, and MBC concentrations in the top 10 cm. In contrast, CT increased MBC contents and bulk density between 20 and 30 cm soil depth. At the Romanian site, soil parameters showed no differences between inverse tillage (CT) and non-inverse tillage (MT), both with a working depth of 25 to 30 cm. At the Spanish site, the use of NT significantly increased the concentrations as well as the stocks of C, N, and MBC compared to CT. In conclusion, reduced tillage improved soil microbial properties in most cases. However, the effectiveness of reduced tillage appears to be highly dependent on site conditions such as pH, soil texture, and climatic conditions.

A study was carried out to gain quantitative information on the diet-dependent faecal microbial biomass of dairy cows, especially on the biomass fractions of fungi, Gram-positive (G+) and Gram-negative (G-) bacteria. Groups of high-yield, low-yield and non-lactating cows were investigated at four different farms. A mean faecal microbial biomass C (MBC) concentration of 33.5 mg g-1 DM was obtained by the chloroform fumigation extraction method. This is similar to a mean microbial C concentration of 31.8 mg g-1 DM, which is the sum of bacterial C and fungal C, estimated by cell-wall derived muramic acid (MurN) and fungal glucosamine (GlcN), respectively. However, the response of these two approaches to the feeding regime was contradictory, due to feeding effects on the conversion values. The higher neutral detergent fibre (NDF) and acid detergent fibre (ADF) concentrations in the non-lactating group led to higher (P < 0.05) concentrations of cellulose and lignin in their faeces in comparison with the lactating cows. This change in faecal chemical composition in the non-lactating group was accompanied by usually higher ratios of G+/G- phospholipid fatty acids (PLFA), ergosterol/MBC and fungal C/bacterial C. Although bacteria dominate the faecal microbial biomass, fungi contribute a considerable mean percentage of roughly 20% to the faecal microbiome, according to PLFA and amino sugar data, which requires more attention in the future. Near-infra red spectroscopic estimates of organic N and C fractions of cow faeces were able to model microbial biomarkers successfully, which might be useful in the future to predict its N2O emission potential and fertilizer value., Competing Interests: The authors have declared that no competing interests exist.

As a consequence of their widespread use, e.g. as protective coatings for fabrics, and their resistance to thermal and biological breakdown, perfluorinated compounds are increasingly found in the environment, but little is known about their ecotoxicological properties. A 40-day microcosm experiment was carried out to examine the effects of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) on the endogeic geophagus earthworm Aporrectodea caliginosa, its survival and feeding on soil organic C and microbial biomass C. Three levels of concentration (1, 100, and 500 mg kg(-1)) were chosen. The lowest represented the maximum found in sediments and soils and the other two are extreme concentrations that might occur in pollution hotspots and that have been shown to poison organisms. Earthworms promoted the production of CO2 and decreased microbial biomass C in soil, regardless of the presence of PFOA or PFOS. Both compounds significantly decreased the surviving numbers and dry weight of earthworms at concentrations of 100 mg kg(-1). No earthworms survived at PFOA and PFOS concentrations of 500 mg kg(-1). At concentrations of 1 mg kg(-1), no negative effects were observed. The δ(13)C values of A. caliginosa did not differ between treatments. In contrast, the δ(15)N values were significantly increased after adding 1 mg kg(-1) of PFOA, reflecting elevated portions of soil-derived N in the earthworm tissue. In contrast, these portions of soil-derived N were lower in the earthworms after addition of 100 mg kg(-1) of PFOA and PFOS. In conclusion, extreme concentrations of PFOA and PFOS negatively affected endogeic A. caliginosa, whereas a concentration of 1 mg kg(-1) of PFOA and PFOS was related to an increased uptake of soil N by the earthworms., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Since more than half of the faecal nitrogen (N) originates from microbial N, the objective of the study was to develop a method for quantitatively detecting microbial biomass and portion of living microorganisms in dairy cattle faeces, including bacteria, fungi and archaea. Three techniques were tested: (1) the chloroform fumigation extraction (CFE) method, (2) detection of the fungal cell-membrane component ergosterol and (3) analysis of the cell wall components fungal glucosamine and bacterial muramic acid. In a second step, an N deficient (ND) and an N balanced (NB) diets were compared with respect to the impacts on faecal C and N fractions, microbial indices and digestibility. The mean values of microbial biomass C and N concentrations averaged around 37 and 4.9 mg g(-1) DM, respectively. Ergosterol, together with fungal glucosamine and bacterial muramic acid, revealed a 25% fungal C in relation to the total microbial C content in dairy cattle faeces. Changes in ruminal N supply showed significant effects on faecal composition. Faecal concentrations of NDF, hemicelluloses and undigested dietary N and the total C/N ratio were significantly higher in ND treatment compared to the NB treatment. N deficiency was reflected also by a higher microbial biomass C/N ratio. It was concluded that the assessment of microbial indices provides valuable information with respect to diet effects on faecal composition and the successive decomposition. Further studies should be conducted to explore the potentials for minimising nutrient losses from faeces.

The present study was conducted to evaluate the changes in microbial biomass indices (C, N, and especially P) and in P fractions in compost amended with inorganic P fertilizers. In the non-amended control, the average contents of microbial biomass C, N, and P were 1744, 193, and 63 microg g(-1) compost, respectively. On average, 1.3% of total P was stored as microbial biomass P. The addition of KH(2)PO(4) and TSP (triple super phosphate) led to immediate significant increases in microbial biomass C, N, and P. Approximately, 4.6% of the added TSP and 5.8% of the added KH(2)PO(4) were incorporated on average into the microbial biomass throughout the incubation. Approximately, 4.7% of the 1mg and 5.8% of the 2mg addition rate were incorporated on average into the microbial biomass. In the amendment treatments, the average contents of microbial biomass C, N, and P declined by 44%, 64%, and 49%, respectively. Initially, the average size of the P fractions in the non-amended compost increased in the order (% of total P in brackets) resin P (0.7%)

Two incubation experiments were conducted to evaluate differences in the microbial use of non-contaminated and heavy metal contaminated nettle (Urtica dioica L.) shoot residues in three soils subjected to heavy metal pollution (Zn, Pb, Cu, and Cd) by river sediments. The microbial use of shoot residues was monitored by changes in microbial biomass C, biomass N, biomass P, ergosterol, N mineralisation, CO(2) production and O(2) consumption rates. Microbial biomass C, N, and P were estimated by fumigation extraction. In the non-amended soils, the mean microbial biomass C to soil organic C ratio decreased from 2.3% in the low metal soil to 1.1% in the high metal soils. In the 42-d incubation experiment, the addition of 2% nettle residues resulted in markedly increased contents of microbial biomass P (+240%), biomass C (+270%), biomass N (+310%), and ergosterol (+360%). The relative increase in the four microbial properties was similar for the three soils and did not show any clear heavy metal effect. The contents of microbial biomass C, N and P and ergosterol contents declined approximately by 30% during the incubation as in the non-amended soils. The ratios microbial biomass C to N, microbial biomass C to P, and ergosterol to microbial biomass C remained constant at 5.2, 26, and 0.5%, respectively. In the 6-d incubation experiment, the respiratory quotient CO(2)/O(2) increased from 0.74 in the low metal soil to 1.58 in the high metal soil in the non-amended soils. In the treatments amended with 4% nettle residues, the respiratory quotient was constant at 1.13, without any effects of the three soils or the two nettle treatments. Contaminated nettle residues led generally to significantly lower N mineralisation, CO(2) production and O(2) consumption rates than non-contaminated nettle residues. However, the absolute differences were small.