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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    European journal of soil science 52 (2001), S. 0 
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The turnover of organic matter determines the availability of plant nutrients in unfertilized soils, and this applies particularly to the alkaline saline soil of the former Lake Texcoco in Mexico. We investigated the effects of alkalinity and salinity on dynamics of organic material and inorganic N added to the soil. Glucose labelled with 14C was added to soil of the former Lake Texcoco drained for different lengths of time, and dynamics of 14C, C and N were investigated with the Detran model. Soil was sampled from an undrained plot and from three drained for 1, 5 and 8 years, amended with 1000 mg 14C-labelled glucose kg−1 and 200 mg NH4+-N kg−1, and incubated aerobically. Production of 14CO2 and CO2, dynamics of NH4+, NO2– and NO3–, and microbial biomass 14C, C and N were monitored and simulated with the Detran model. A third stable microbial biomass fraction had to be introduced in the model to simulate the dynamics of glucose, because 〉 90 mg 14C kg−1 soil persisted in the soil microbial biomass after 97 days. The observed priming effect was mostly due to an increased decay of soil organic matter, but an increased turnover of the microbial biomass C contributed somewhat to the phenomenon. The dynamics of NH4+ and NO3– in the NH4+-amended soil could not be simulated unless an immobilization of NH4+ into the microbial biomass occurred in the first day of the incubation without an immediate incorporation of it into microbial organic material. The dynamics of C and a priming effect could be simulated satisfactorily, but the model had to be adjusted to simulate the dynamics of N when NH4+ was added to alkaline saline soils.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0789
    Keywords: Key words Alkaline saline soils ; Micro-organisms ; Characteristics ; C and N mineralization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Soils from the former Lake Texcoco are alkaline saline and were artificially drained and irrigated with sewage effluents since the late 1980s. Undrained soil and soil drained for 1, 5 and 8 years were sampled, characterized and incubated aerobically for 90 days at 22±1  °C while production of CO2, available P and concentrations of NH4 +, NO2 – and NO3 – were monitored. Artificial drainage decreased pHH2O, water holding capacity, organic C, total N, and Na+, K+, Mg2+, B, Cl– and SO4 2– concentrations, increased inorganic C and Ca2+ concentrations more than 5-fold while total P was not affected. Microbial biomass C decreased with increased length of drainage but bacteria, actinomycetes, denitrifiers and cellulose-utilizing bacteria tended to show opposite trends. CO2 production was less in soils drained ≥5 years compared to undrained soil but more than in soils drained for 1 year. Emission of NH3 was negligible and concentrations of NH4 + remained constant over time in each soil. Nitrification, as witnessed by increases in NO3 – concentrations, occurred in soil drained for 8 years. NO2 – concentrations decreased in soils drained ≤1 year in the first 7 days of the incubation and remained constant thereafter. It was found that artificial drainage of soils from the former Lake Texcoco profoundly affected soil characteristics. Decreases in pH and Na+, K+, Cl– and SO4 2– concentrations made conditions more favourable for plant growth, although low concentrations of inorganic N and available P might be limiting factors.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0789
    Keywords: Key words Mesquite ; Carbon dioxide production ; Nitrogen mineralization ; Microbial biomass carbon ; Nitrous oxide production
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  In the central highlands of Mexico, the vegetation is dominated by mesquite (Prosopis spp.), a leguminous tree or shrub. An experiment was carried out to investigate how cultivating the land and the disappearance of the natural ecosystem affected the biological functioning of the soil. Soil was sampled from under the canopy of isolated (MESQ treatment) and densely growing mesquite trees (DENS treatment), from the surrounding soil not covered by the canopies of the trees (BARE treatment) and from adjacent land cultivated with maize (ARABLE treatment). Soil was characterized and then incubated aerobically for 39 days at 22±1  °C and CO2, N2O production, microbial biomass C and inorganic N concentrations were monitored. The organic C content was 2.3 times and 1.1 times greater in the MESQ and the BARE treatments, respectively, than in the ARABLE treatment, while microbial biomass C was 3.5 times and 1.3 times greater. The microbial biomass activity as expressed by CO2 production was 5.9 times and 3.9 times greater in the MESQ and the BARE treatments, respectively, than in the ARABLE treatment, while N mineralization, as witnessed by the increase in NO3 – concentrations, was 3.4 times and 1.7 times greater. No significant amounts of N2O were produced in any of the treatments. It was found that cultivating land characterized by the presence of mesquite changed its characteristics profoundly, and even soil not covered by tree canopies had higher microbial biomass C, and C and N mineralization than soil cultivated with maize and beans.
    Type of Medium: Electronic Resource
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