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  • CO2 evolution  (1)
  • Chloroform fumigation incubation  (1)
  • redox  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Freeze-dried soil extraction method for the measurement of microbial biomass C (1997)
    Springer
    Biology and fertility of soils 24 (1997), S. 205-210 
    Details
    ISSN: 1432-0789
    Keywords: Key words Freeze-drying ; Microbial biomass C ; K2SO4 extractable C ; NaHCO3 extractable C ; Chloroform fumigation incubation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A new method for the measurement of microbial biomass C by direct extraction of freeze-dried soil with either 0.5M K2SO4 or 0.5M NaHCO3 was evaluated. The underlying principle of the method is that rehydrating a freeze-dried soil releases cytoplasmic organic compounds from desiccated and disrupted microbial cells. Nineteen soils under various management regimes were sampled to test the proposed method, in which each soil sample was split into two subsamples. One subsample was kept in the field-moist condition at 4°C. The other subsample was brought to 100% water-holding capacity and frozen at –20°C for 24h. The frozen soil was then freezedried. Both subsamples were extracted with 0.5M K2SO4 or 0.5M NaHCO3 at a soil-to-extractant ratio of 1-to-4 (w/v) and organic C determined in the extract (CK2 SO4 or CNaHCO3). The net freeze-dry stimulated increase in extracted C was correlated (r 2=0.98 for CK2 SO4 or 0.93 for 〈$〉\rm C_{NaHCO_3})〈$〉 more closely with microbial biomass C (CMB) measured as net evolution of CO2–C by chloroform fumigation incubation (CFI) than with total C (r 2=0.42 for CK2 SO4 or 0.47 for CNaHCO3). Based on linear regression equations, extraction efficiency coefficients (K EC) were used to calculate CMB from CK2 SO4 or CNaHCO3 as follows: CMB=CK2 SO4/0.152±0.004 CMB=CNaHCO3/0.257±0.01 The relationship between the CMB and the flushes of C extracted after rehydration of freeze-dried soil showed that the K EC values were more consistent for CK2 SO4 than CNaHCO3. The freeze-dried soil extraction was a fast, precise, reliable and safe method for measuring microbial biomass C in soil.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050232
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Microwave irradiation of soil for routine measurement of microbial biomass carbon (1998)
    Springer
    Biology and fertility of soils 27 (1998), S. 408-416 
    Details
    ISSN: 1432-0789
    Keywords: Key words Microwave irradiation ; Microbial biomass C ; CO2 evolution ; K2SO4 extractable C ; Chloroform-fumigation incubation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Microwave irradiation was evaluated as a non-toxic alternate to chloroform fumigation for routine measurement of soil microbial biomass C. Microwave energy was applied to moist soil to disrupt microbial cells. The flush of C released was then measured after extraction or incubation. Microwave irradiation at 800 J g–1 soil was optimal because this level resulted in an almost instantaneous rise in soil temperature (≥80  °C), an abrupt reduction in microbial activity, maximal release of biomass C, and minimal solubilization of humic substances. Both incubation-CO2 titration and extraction-colorimetry methods were used on separate 20-g subsamples to compare the labile C in the microwave-treated and untreated soil samples. The incubation-titration method was also used to measure C in chloroform-fumigated soil samples. Averaged across soils, the chloroform fumigation yielded 123.3±5.1 mg CO2-C kg–1. Microwave irradiation yielded 93.6±3.9 mg CO2-C kg–1 soil determined by incubation and 52.4±2.4 mg C kg–1 soil determined by extraction, accounting for 76% and 42% of the net flush of C measured by the chloroform fumigation. Microwave-stimulated net flushes of C were correlated closely (r 2=0.974 for incubation or 0.908 for extraction) with microbial biomass C measured by the chloroform fumigation. Little correlation was found with the total soil organic C (r 2=0.241 for incubation or for 0.166 extraction). Mean efficiency factors for incubation (K MI) or extraction (K ME) were used to calculate microbial biomass C from net flushes of C between microwaved and unmicrowaved soils. Values of K MI and K ME were not affected by soil pH, bulk density or clay contents. Extraction of microwaved soil by 0.5M K2SO4 proved to be a simple, fast, precise, reliable, and safe method to measure soil microbial biomass C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050451
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of submergence on availability of certain plant nutrients in three Ultisol catenas (1989)
    Springer
    Plant and soil 114 (1989), S. 147-157 
    Details
    ISSN: 1573-5036
    Keywords: copper ; DTPA ; flooded ; iron ; manganese ; redox ; rice ; soil catena ; waterlogged ; zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Soil samples from surface and sub-surface horizons in the well-drained and poorly-drained members of three soil catenas were incubated under submergence or at field capacity to study the effects of these incubation conditions and prior natural drainage on the solubility of four plant micro-nutrients. Iron, Mn, Zn and Cu were extracted by water using a 1∶1 water:soil ratio. The four micronutrient metals were also extracted by DTPA solutions buffered at either pH 5.3 or pH 7.3 to compare the effectiveness of these two extractants under these incubation conditions with acid soils. Generally the extractability of the nutrients was much affected by the horizon (A, E or B) with A horizons having the greatest amounts of all nutrients and undergoing greater changes in water- and DTPA-extractability during incubation. Soil drainage class (wellvs. poorly drained) had few effects. Incubation moisture regime had major effects on water extractable Fe and Mn with lesser effects on Zn and Cu. Submerged soils generally had the greatest levels of water extractable nutrients, though rice uptake did not reflect this. DTPA at pH 5.3 extracted 2 to 3 times as much Fe, Mn, Zn and Cu as did DTPA at pH 7.3 and about 50 to 100 times as much as did water. Correlations between DTPA extractable nutrients and rice uptake were significant only for Fe and Cu and declined during incubation. The changes in all variables during incubation were complex, being related to soil properties such as organic matter content, pH and mineralogy as well as to incubation conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02220793
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    Paper (German National Licenses)
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