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1.
Amending soils with glucose (5 mg g?1) resulted in an immediate increase in microbial activity and within 30 min the rates of heat output and respiration at 22° C were increased by up to 17.8 and 23.4 times, respectively. The increased rate of heat output remained stable for up to 6 h and there was good correlation with the amount of CO2 respired. The soil biomass was calculated by the method of Anderson and Domsch (1978). The rate of heat output of the biomass varied in different soils and ranged from 11.5 to 83.7 Jh?1 g?1 biomass C. In glucose-amended soils, however, the rate of heat output was much more consistent; the soils were in two groups having between 169–265 Jh?1g?1 biomass C or 454–482 J h?1 g?1 biomass C, both the latter two soils were from pasture. The increased rate of heat output from the amended soils was lower than expected from the respiration rate and the heat of oxidation of glucose, suggesting that a proportion of the CO2 respired was from catabolism of substrates other than glucose. Use of 14C-glucose confirmed that between 57–91% of the CO2 was derived from the glucose substrate.  相似文献   

2.
Four contrasting soils were amended with glucose at concentrations up to 10 mg g?1 soil. The soils were incubated at 22°C for 14 days and the biomass determined at various times by chloroform fumigation or substrate-induced respiration. The adenosine triphosphate (ATP) content or the amylase and dehydrogenase activities were also determined. The size of the increases in biomass, ATP content and the enzyme activities was generally related to the amount of glucose added. The initially higher ATP levels quickly declined, and apparent substrate conversion figures up to 84% indicated that substrate-induced respiration overestimated the biomass. There were generally no significant correlations between ATP, biomass or enzyme activities.  相似文献   

3.
Most important, yet least understood, question, how microbial activity in soil under saline water irrigation responds to carbon (C) varying qualitatively (most labile form to extreme recalcitrant form) with or without maintaining C/N ratio was investigated in an incubation experiment. Soil samples from a long-term saline-water (electrical conductivity, EC ≈ 0, 6, and 12 dS m?1)- irrigated field were incorporated with three different C substrates, viz., glucose, rice straw (RS), and biochar with or without nitrogen (N as ammonium sulfate, NH4SO4) and were incubated at 25 °C for 56 days. Cumulative respiration (CR), microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and dehydrogenase activity (DEA) concentrations decreased with increasing EC (P < 0.05), but less so in soils amended with glucose followed by RS and biochar. The addition of N to soils amended with different C substrates significantly decreased CR, MBC, DEA, and available phosphorus (P) concentrations at a given EC level.  相似文献   

4.
Abstract

On air‐drying, the ATP contents of two moist soils fell to about one quarter of their original values. When a freshly‐sampled soil (field temperature 5.5°C) was stored moist (43% water holding capacity) for 7 days at 25°C the ATP content increased from 4.54 to 7.84 μg ATP g‐1 soil. Storage at 10°C caused a smaller increase; to 5.39 μg g‐1 soil. Microbial biomass C also increased on storage but the relative increase was less than that of ATP. Thus the biomass C/ATP ratio fell from 234 in the freshly sampled soil to 168 in the soil stored moist for 7 days at 25°C. The ATP content declined to less than half its starting value if storage was under waterlogged conditions.

The ATP method for determining microbial biomass in soil depends on the use of a constant factor (5.85 mg ATP g‐1 biomass C) for converting ATP content to biomass C. This factor came from work on soils that had been stored moist at 25°C for several days before biomass C and ATP measurements were made: it is only applicable to soils that have been stored in this way.  相似文献   

5.
The potential of Nostoc 9v for improving the nitrogen (N)2–fixing capacity and nutrient status of semi‐arid soils from Tanzania, Zimbabwe, and South Africa was studied in a laboratory experiment. Nostoc 9v was inoculated on nonsterilized and sterilized soils. Inoculum rates were 2.5 mg dry biomass g?1 soil and 5 mg dry biomass g?1 soil. The soils were incubated for 3 months at 27 °C under 22 W m2 illumination with a photoperiod of 16 h light and 8 h dark. The moisture was maintained at 60% of field capacity. In all soils, Nostoc 9v proliferated and colonized the soil surfaces very quickly and was tolerant to acidity and low nutrient availability. Cyanobacteria promoted soil N2 fixation and had a pronounced effect on total soil organic carbon (SOC), which increased by 30–100%. Total N also increased, but the enrichment was, in most soils, comparatively lower than for carbon (C). Nitrate and ammonium concentrations, in contrast, decreased in all the soils studied. Increases in the concentration of available macronutrients were produced in most soils and treatments, ranging from 3 to 20 mg phosphorus (P) kg?1 soil, from 5 to 58 mg potassium (K) kg?1 soil, from 4 to 285 mg calcium (Ca) kg?1, and from 12 to 90 mg magnesium (Mg) kg?1 soil. Positive effects on the levels of available manganese (Mn) and zinc (Zn) were also observed.  相似文献   

6.
Investigations of diurnal and seasonal variations in soil respiration support modeling of regional CO2 budgets and therefore in estimating their potential contribution to greenhouse gases. This study quantifies temporal changes in soil respiration and their driving factors in grassland and arable soils located in Northern Germany. Field measurements at an arable site showed diurnal mean soil respiration rates between 67 and 99 mg CO2 m–2 h–1 with a hysteresis effect following changes in mean soil temperatures. Field soil respiration peaked in April at 5767 mg CO2 m–2 day–1, while values below 300 mg CO2 m–2 day–1 were measured in wintertime. Laboratory incubations were carried out in dark open flow chambers at temperatures from 5°C to 40°C, with 5°C intervals, and soil moisture was controlled at 30%, 50%, and 70% of full water holding capacity. Respiration rates were higher in grassland soils than in arable soils when the incubating temperature exceeded 15°C. The respiration rate difference between them rose with increasing temperature. Monthly median values of incubated soil respiration rates ranged from 0 to 26.12 and 0 to 7.84 µg CO2 g–1 dry weight h–1, respectively, in grassland and arable land. A shortage of available substrate leads to a temporal decline in soil respiration rates, as indicated by a decrease in dissolved organic carbon. Temporal Q10 values decreased from about 4.0 to below 1.5 as temperatures increased in the field. Moreover, the results of our laboratory experiments confirmed that soil temperature is the main controlling factor for the Q10 values. Within the temperature interval between 20°C and 30°C, Q10 values were around 2 while the Q10 values of arable soils were slightly lower compared to that of grassland soils. Thus, laboratory studies may underestimate temperature sensitivity of soil respiration, awareness for transforming laboratory data to field conditions must therefore be taken into account.  相似文献   

7.
Agricultural soil CO2 emissions and their controlling factors have recently received increased attention because of the high potential of carbon sequestration and their importance in soil fertility. Several parameters of soil structure, chemistry, and microbiology were monitored along with soil CO2 emissions in research conducted in soils derived from a glacial till. The investigation was carried out during the 2012 growing season in Northern Germany. Higher potentials of soil CO2 emissions were found in grassland (20.40 µg g?1 dry weight h?1) compared to arable land (5.59 µg g?1 dry weight h?1) within the incubating temperature from 5°C to 40°C and incubating moisture from 30% to 70% water holding capacity (WHC) of soils taken during the growing season. For agricultural soils regardless of pasture and arable management, we suggested nine key factors that influence changes in soil CO2 emissions including soil temperature, metabolic quotient, bulk density, WHC, percentage of silt, bacterial biomass, pH, soil organic carbon, and hot water soluble carbon (glucose equivalent) based on principal component analysis and hierarchical cluster analysis. Slightly different key factors were proposed concerning individual land use types, however, the most important factors for soil CO2 emissions of agricultural soils in Northern Germany were proved to be metabolic quotient and soil temperature. Our results are valuable in providing key influencing factors for soil CO2 emission changes in grassland and arable land with respect to soil respiration, physical status, nutrition supply, and microbe-related parameters.  相似文献   

8.
A simple method to measure soil ATP by the luciferin-luciferase system is described. The ATP is extracted from the soil by vigorous shaking with a sulfuric acid-phosphate solution for 15 min. An aliquot of the soil suspension is neutralized with a Tris-EDTA solution and mixed with a special ATP releasing reagent (NRB). ATP is measured after a 10 s exposure to the NRB reagent, followed by addition of luciferin-luciferase and integration over 10 s in a Lumacounter M 2080. The ATP content in soils which had been stored at 5°C for 90 days and then incubated at 25°C for 5 days, ranged from 0.37 to 7.52 μg ATP g?1 dry wt, with standard deviations less than 10%. There was a close (r = 0.96) linear relationship between ATP content and biomass C determinated by fumigation for this group of soils. The soil biomass contained 4.2–7.1 μg ATP mg?1 biomass C. The ATP content of the biomass declined during storage at 5°C for 210 days.  相似文献   

9.
Reclamation of sodic soils is proving increasingly vital as greater land area becomes salt-affected in the northern Great Plains of the United States. Flue gas desulfurization gypsum (FGDG) can be an agriculturally important resource for increasing land productivity through the amelioration of sodic soils. Biochar is also considered as an aid in reclaiming degraded soils. In this incubation study, two rates of FGDG (33.6 Mg ha?1 and 66.2 Mg ha?1), two rates of biochar made from sugar beet (Beta vulgaris L.) pulp (16.8 Mg ha?1), and one rate of FGDG combined with one rate of biochar (33.6 Mg ha?1 ea.) were applied to a sodic soil. Soil physicochemical properties, including cationic exchange, pH, electrical conductivity (ECe), sodium adsorption ratio (SARe), total organic carbon (TOC), water retention, and soil respiration rate, were assessed during and at the end of the incubation period. Addition of FGDG to sodic soil increased ECe from 3.5 to 8.4 dS m?1 and decreased SARe from 16 to 9. Biochar addition to sodic soil increased TOC from 62.2 to 99.5 μg g?1 and increased soil respiration rate (mg C kg?1 soil day?1) on every measurement period. When FGDG and biochar were both added to the sodic soil, TOC did not significantly improve; however, ECe increased from 3.5 to 7.7 dS m?1, SARe decreased from 16 to 9, and soil respiration rate increased for all measurements. The results confirm there is potential for FGDG and biochar to reclaim sodic soils alone, and applied in combination.  相似文献   

10.
In order to characterise the term microbial ?activity”? three different microbial populations belonging to a luvisol (I), a phaeozem (II) and a rendzina (III) were used for studying kinetic parameters such as substrate affinity, growth rate, yield and turnover time and the metabolic quotient of basal respiration. Glucose was used as a carbon source. Specific growth rate values (μ) varied between 0.0037 and 0.015 h?1 depending on soil type and glucose concentration and were far below the potential μmax. The calculated turnover time was 3–11 days, respectively. The yield coefficient was in the range between 0.37 and 0.53. The maximal uptake rate of glucose–C of soil population (II) was 0.041 g C g?1 biomass-C h?1. The determined affinity constant (Km) was 57 μg C g?1 soil. The affinity to glucose was higher for the glucose-mediated CO2 evolution with Km values of 15.2 and 17.5 than for the glucose uptake system itself. The observed qCO2 values of the basal respiration at temperature increments from 0 to 45° C were almost identical for the soils (I) and (II). The calulated Q10 lay in the range between 1.4 and 2.0.  相似文献   

11.
Low molecular weight (LMW) organic compounds in soil solution are easily biodegradable and could fuel respiration by soil microorganisms. Our main aim was to study the mineralization kinetics of monosaccharides using 14C-radiolabelled glucose. Based on these data and the soil solution concentrations of monosaccharides, we evaluated the contribution of monosaccharides to basal respiration for a variety of tropical forest soils. Further, the factors controlling the mineralization kinetics of monosaccharides were examined by comparing tropical and temperate forest soils. Monosaccharides comprised on average 5.2 to 47.7% of dissolved organic carbon in soil solution. Their kinetic parameters (V max and KM ), which were described by a single Michaelis-Menten equation, varied widely from 11 to 152?nmol?g?1?h?1 and 198 to 1294?µmol?L?1 for tropical soils, and from 182 to 400?nmol?g?1?h?1 and 1277 to 3150?µmol?L?1 for temperate soils, respectively. The values of V max increased with increasing microbial biomass-C in tropical and temperate soils, while the KM values had no correlations with soil biological or physicochemical properties. The positive correlation between V max values and microbial biomass-C indicates that microbial biomass-C is an essential factor to regulate the V max values in tropical and temperate forest soils. The biodegradation kinetics of monosaccharides indicate that the microbial capacity of monosaccharide mineralization far exceeds its rate at soil solution concentration. Monosaccharides in soil solution are rapidly mineralized, and their mean residence times in this study were very short (0.4–1.9?h) in tropical forests. The rates of monosaccharide mineralization at actual soil solution concentrations made up 22–118% of basal respiration. Probably because of the rapid and continuous production and consumption of monosaccharides, monosaccharide mineralization is shown to be a dominant fraction of basal respiration in tropical forest soils, as well as in temperate and boreal forest soils.  相似文献   

12.
Impacts of crop residue biochar on soil C and N dynamics have been found to be subtly inconsistent in diverse soils. In the present study, three soils differing in texture (loamy sand, sandy clay loam and clay) were amended with different rates (0%, 0.5%, 1%, 2% and 4%) of rice-residue biochar and incubated at 25°C for 60 days. Soil respiration was measured throughout the incubation period whereas, microbial biomass C (MBC), dissolved organic C (DOC), NH4+-N and NO3–N were analysed after 2, 7, 14, 28 and 60 days of incubation. Carbon mineralization differed significantly between the soils with loamy sand evolving the greatest CO2 followed by sandy clay loam and clay. Likewise, irrespective of the sampling period, MBC, DOC, NH4+-N and NO3–N increased significantly with increasing rate of biochar addition, with consistently higher values in loamy sand than the other two soils. Furthermore, regardless of the biochar rates, NO3–-N concentration increased significantly with increasing period of incubation, but in contrast, NH4+-N temporarily increased and thereafter, decreased until day 60 in all soils. It is concluded that C and N mineralization in the biochar amended soils varied with the texture and native organic C status of the soils.  相似文献   

13.
Zinc as ZnSO4 was added to three soils at rates of 0, 10, 100 and 1000 μg Zn g?1 soil. The soils were uniformly treated with 100 μg Ng?1 as nh4cl, incubated at 30°C and NH4+-N and (NO3? + NO2?)-N determined weekly for 7 weeks. Nitrification in all three soils was totally inhibited by 1000 μg Zn g?1. At the 100 μg Zn g?1 rate, nitrification was significantly reduced in two of the three soils during some part of the incubation. This differential effect on nitrification at the 100 μg Zn g?1 rate was related to differences in soil properties. These results imply that, with respect to nitrification, care should-be taken not to apply Zn-containing materials indiscriminately to soils.  相似文献   

14.
Microbial biomass, respiratory activity, and in‐situ substrate decomposition were studied in soils from humid temperate forest ecosystems in SW Germany. The sites cover a wide range of abiotic soil and climatic properties. Microbial biomass and respiration were related to both soil dry mass in individual horizons and to the soil volume in the top 25 cm. Soil microbial properties covered the following ranges: soil microbial biomass: 20 µg C g–1–8.3 mg C g–1 and 14–249 g C m–2, respectively; microbial C–to–total organic C ratio: 0.1%–3.6%; soil respiration: 109–963 mg CO2‐C m–2 h–1; metabolic quotient (qCO2): 1.4–14.7 mg C (g Cmic)–1 h–1; daily in‐situ substrate decomposition rate: 0.17%–2.3%. The main abiotic properties affecting concentrations of microbial biomass differed between forest‐floor/organic horizons and mineral horizons. Whereas microbial biomass decreased with increasing soil moisture and altitude in the forest‐floor/organic horizons, it increased with increasing Ntot content and pH value in the mineral horizons. Quantities of microbial biomass in forest soils appear to be mainly controlled by the quality of the soil organic matter (SOM), i.e., by its C : N ratio, the quantity of Ntot, the soil pH, and also showed an optimum relationship with increasing soil moisture conditions. The ratio of Cmic to Corg was a good indicator of SOM quality. The quality of the SOM (C : N ratio) and soil pH appear to be crucial for the incorporation of C into microbial tissue. The data and functional relations between microbial and abiotic variables from this study provide the basis for a valuation scheme for the function of soils to serve as a habitat for microorganisms.  相似文献   

15.
Though engineered covers have been suggested for reducing landfill methane emissions via microbial methane oxidation, little is known about the covers' function at low temperature. This study aimed to determine the methane consumption rates of engineered soil columns at low temperature (4–12°C) and to identify soil characteristics that may enhance methane oxidation in the field. Engineered soils (30 cm thick) were mixtures of sewage sludge compost and de-inking waste, amended with sand (SDS soil) or bark chips (SDB soil). At 4–6°C, we achieved rates of 0.09 gCH4 kgTS?1d?1 (0.02 m3 m?2d?1) and 0.06 gCH4 kgTS?1d?1 (0.009 m3 m?2d?1) with SDS and SDB soils, respectively. With SDS, good movement and exchange of oxygen in porous soil moderated the slowdown of microbial activity so that the rate dropped only by half as temperature declined from 21–23°C to 4–6°C. In SDB, wet bark chips reduced the soil's air-filled porosity and intensified non-methanotrophic microbial activity, thus reducing the methane consumption rate at 4–6°C to one fourth of that at 21–23°C. In conclusion, soil characteristics such as air-filled porosity, water holding capacity, quantity and stabilization of organic amendments that affect the movement and exchange of oxygen are important variables in designing engineered covers for high methane oxidation at low temperature.  相似文献   

16.
The effects of vermicompost (VC) (0% and 1% w/w) on treated calcareous clay soil with 0 and 50 mg phosphorus (P) kg?1 as calcium phosphate [Ca(H2PO4)2.H2O] was investigated. The soil samples were incubated for 7, 30, 60, 120, and 150 d at 25 ± 1°C and Olsen-P was measured after each incubation time. Results showed that Olsen-P increased 36% and 38% after VC addition in treated soil with 0 and 50 mg P kg?1, respectively. Recovery of Olsen-P in treated soils with VC, combined fertilizer VC + P, and fertilizer P was 42%, 42%, and 17%, respectively. The rate coefficient in treated soils with fertilizer, VC, and combined fertilizer VC + P was 0.033, 0.026, and 0.023 mg kg?1 d?1/2, respectively. It seems that the process that leads to the decrease in available P in amended soils, is controlled by P diffusion into sorption sites in micropores of aggregates.  相似文献   

17.
Bacteria, Pseudomonas paucimobilis, were inoculated at two concentrations (6.56 × 104 g?1 and 6.56 × 106g?1) into sterilized soil amended with 700 μg glucose-C g?1. Two levels of NH+4-N (11.0μg g?1 and 81.0 μg g?1) were used. The subsequent development was followed for three days by measurement of several biological, chemical and physiological parameters.The amount of bacterial biomass-C (μg g?1 soil) became twice as great in high as in low N treatments, and significantly decreased between 39.5 and 63.5 h for the high inoculum, high N level treatment due to decreasing cell size. By the end of the experiment the cumulative respired carbon was twice as great and more inorganic P was immobilized for high compared to low N treatments and all available NH+4-N was taken up by the final sample time. Soil ATP concentrations were twice as large in high N treatments but the turnover times were twice as long compared to low N systems. The yield coefficient (Y), calculated from respiration and biomass-C values, equalled 0.61 while substrate was plentiful. Nitrogen limitation did not alter the efficiencey with which glucose was transformed into biomass, but rather controlled the total amount of glucose used and biomass produced.  相似文献   

18.
A sandy soil was amended with different types of sewage sludge (digested, dried, and composted) and pig slurry. The composted sludges displayed higher organic‐matter stability (39–45%) than only digested sludge (26–39%) or digested + dried sludge (23–32%). The microbial biomass of the dried sludge was undetectable. Digested and composted sludges and pig slurry displayed microbial biomasses (12492–13887 µg g?1, 1221–2050 µg g?1, and 5511 µg g?1, respectively) greater than the soil (108 µg g?1). The wastes were applied at seven doses, ranging from 10 to 900 g kg?1. Soils were incubated for 28 days. Substrate‐induced respiration (SIR) was measured for 12 consecutive hours on day 1 and on day 28. The results showed that SIR increased with the dose of organic amendment. However, SIR decreased when moderate doses of pig slurry or high doses of digested + dried sludge were tested. The possibility of using this inhibition as an ecotoxicological indicator is discussed.  相似文献   

19.
In saline soils under semi-arid climate, low matric and osmotic potential are the main stressors for microbes. But little is known about the impact of water potential (sum of matric and osmotic potential) and substrate composition on microbial activity and biomass in field collected saline soils. Three sandy loam soils with electrical conductivity of the saturated soil extract (ECe) 3.8, 11 and 21 dS m?1 (hereafter referred to EC3.8, EC11 and EC21) were kept at optimal water content for 14 days. After this pre-incubation, the soils were either left at optimal water content or dried to achieve water potentials of ?2.33, ?2.82, ?3.04 and ?4.04 MPa. Then, the soils were amended with 20 g?kg?1 pea or wheat residue to increase nutrient supply. Carbon dioxide emission was measured over 14 days; microbial biomass C was measured at the end of the experiment. Cumulative respiration decreased with decreasing water potential and was significantly (P?<?0.05) lower in soils at water potential ?4 MPa than in soils at optimal water content. The effect of residue type on the response of cumulative respiration was inconsistent; with residue type having no effect in the saline soils (EC11 and EC21) whereas in the non-saline soil (EC3.8), the decrease in respiration with decreasing water potential was less with wheat than with pea residue. At a given water potential, the absolute and relative (in percentage of optimal water content) cumulative respiration was lower in the saline soils than in the non-saline soil. This can be explained by the lower osmotic potential and the smaller microbial biomass in the saline soils. However, even at a similar osmotic potential, cumulative respiration was higher in the non-saline soil. It can be concluded that high salt concentrations in the soil solution strongly reduce microbial activity even if the water content is relatively high. The stronger relative decrease in microbial activity in the saline soils at a given osmotic potential compared to the non-saline soil suggests that the small biomass in saline soils is less able to tolerate low osmotic potential. Hence, drying of soil will have a stronger negative effect on microbial activity in saline than in non-saline soils.  相似文献   

20.
Abstract

A micro-plot 15N-tracer experiment was established in three different soils of a long-term soil fertility field experiment. The nutrient-poor loam sand has been subjected to various treatments over the years and this has resulted in different organic C (0.35% – 0.86%), microbial biomass (38.3 – 100.0 µg C mic g?1 soil), clay and fine silt contents. Using the 15N-pool dilution technique, we assessed gross N-transfer rates in the field. Gross N mineralization rates varied strongly among the three plots and ranged between 0.4 and 4.2 µg N g?1 soil d?1. Gross nitrification rates were estimated to be between 0 and 2.1 µg N g?1 soil d?1. No correlation between gross N mineralization rates and the organic matter content of the soils was established. However, gross nitrate consumption rates increased with increasing soil C content. The 15N-pool dilution technique was successfully used to measure gross N transfer rates directly in the field.  相似文献   

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