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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 177 (1995), S. 175-181 
    ISSN: 1573-5036
    Keywords: aerobic incubation ; nitrogen mineralization potential ; Stanford and Smith
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Soil is often incubated under controlled conditions to assess its capacity to mineralize nitrogen and to define the N mineralization potential (No) by fitting a negative exponential curve to N mineralization data. The specificity of No for a given soil and its relevance in N mineralization studies was examined as part of an overall study of the N mineralization process. Soil mixed with an equal amount of sand was aerobically incubated at 35 °C and leached at specific time intervals. Upon leaching, ammonium and nitrate were measured in the extract. It was found that N mineralization data did not always follow first-order kinetics making it difficult to calculate No. The computed No value was influenced by the shape of the curve, the duration of the incubation experiment and was reciprocally related to the N mineralization constant (kexp). No did not always give an adequate indication of the amount of N mineralized and was not soil specific as the time of sampling largely affected its size. The usefulness of No in the simulation of the N mineralization process with a kexp value valid for all soils was limited and a kexp value specific for each soil was required. A value combining the soil specific No and kexp values and reflecting the amount of N mineralized over one year was proposed as a suitable alternative to the use of No in comparative studies of the N mineralization process. It was concluded that a calculated No could not be used in studies comparing the N mineralization of different soils. In addition, the simulation of the N mineralization required the use of the soil specific kexp and could not be carried out with a kexp valid for all soils.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5036
    Keywords: aerobic incubation ; C and N mineralization ; crop residues ; soil organic matter pools ; Stanford and Smith
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Fitting a double negative exponential function to N mineralization data can be used to characterize two organic nitrogen pools; an ‘easily’ decomposable (Ndpm) and a ‘resistant’ one (Nrpm). The relevance of those two calculated N mineralization pools was investigated by adding ‘easily’ decomposable organic material to soils. Soil amended with crop residues of sugar-beet or bean was mixed with an equal amount of coarse sand, incubated at 35 °C and leached at specific time-intervals. Upon leaching, NH4 + and NO3 - were measured in the extracts. A double negative exponential function was fitted to the data and two organic N pools were defined. Fitting a double negative exponential function to N mineralization data to characterize an active and resistant organic N pool was sometimes impossible; the N mineralization data did not always resemble a negative exponential function. Additionally, the size of the two pools calculated were not constant with time and were often meaningless; the Nrpm pool was greater than the soil organic N content, the size of the Nrpm pool was smaller than the Ndpm pool or one of the N pools was negative. Relevant values for both Nrpm and Ndpm which were consistent with incubation time were only obtained when excessive amounts of organic material, normally not dealt with in the field, were applied.
    Type of Medium: Electronic Resource
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