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  • 1
    ISSN: 1432-0789
    Schlagwort(e): Key words Humic substances ; Cucumber ; Iron nutrition ; Iron deficiency ; Root acidification
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The capacity of Fe-deficient cucumber plants to utilise water-extractable and pyrophosphate-extractable humic substances as a source of Fe was investigated. Plants were grown for 13 days in nutrient solution in the presence or absence of Fe and during the last 7 days water-extractable and pyrophosphate-extractable humic substances were added to the solution at a final concentration of 5 μg organic C ml–1. The water-extractable humic fraction did not significantly modify leaf area and dry matter accumulation, leaf total Fe or chlorophyll content of cucumber plants adequately supplied with Fe. In contrast, pyrophosphate-extractable humic substances caused a slight but significant decrease of all the leaf parameters considered, with the exception of the chlorophyll content. Root Fe content of Fe-sufficient plants was decreased by more than 50% in the presence of each humified fraction. Addition of each humic fraction to Fe-deficient plants led to a partial disappearance of leaf chlorosis symptoms with a significant increase in chlorophyll and leaf Fe content. Fe content of roots was also significantly increased in Fe-deficient plants by the addition of humic substances to the nutrient solution. These results show that Fe-deficient cucumber plants can utilise Fe contained in the two fractions of humified organic matter. However, by calculating the amount of total Fe accumulated per plant in the presence of water-extractable or pyrophosphate-extractable humic substances, it could be seen that Fe contained in the water-extractable humic fraction was almost totally used by Fe-deficient cucumber plants, while that present in the pyrophosphate-extractable fraction could only be partially absorbed. The results strongly support a role of humified organic matter in Fe nutrition of plants and are discussed in terms of a possible interaction between soil humic substances and the biochemical mechanisms involved in the plant response to Fe deficiency.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    ISSN: 1432-0789
    Schlagwort(e): Key words Organic fertilization ; Soil microbial biomass carbon ; Metabolic quotient ; Bioavailability ; Heavy metals
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract  We studied the long-term effects (12 years) of municipal refuse compost addition on the total organic carbon (TOC), the amount and activity of the microbial biomass (soil microbial biomass C, BC and metabolic quotient qCO2) and heavy metal bioavaiability in soils as compared to manuring with mineral fertilizers (NPK) and farmyard manure (FYM). In addition, we studied the relationships between among the available fraction [Diethylenetriaminopentacetic acid (DTPA) extractable] of heavy metals and their total content, TOC and BC. After 12 years of repeated treatments, the TOC and BC of control and mineral fertilized plots did not differ. Soils treated with FYM and composts showed a significant increase in TOC and BC in response to the increasing amounts of organic C added. Values of the BC/TOC ratio ranged from 1.4 to 2, without any significative differences among soil treatments. The qCO2 increased in the organic-amended soil and may have indicated microbial stress. The total amounts of metals in treated soils were lower than the levels permitted by the European Union in agricultural soils. DTPA-extractable metals increased in amended soils in response to organic C. A multiple regression analysis with stepwise selection of variables was carried out in order to discriminate between the influence exerted on DTPA-extractable metals by their total content, TOC and BC. Results showed that each metal behaved quite differently, suggesting that different mechanisms might be involved in metal bioavailability
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 105 (1988), S. 41-46 
    ISSN: 1573-5036
    Schlagwort(e): extraction ; numification index ; isoelectric focusing ; organic matter ; worm cast
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The humification index (HI) values of three different manures and earthworm casts were calculated for three different extractant solutions (0.5M sodium hydroxide, 0.1M sodium pyrophosphate pH 7 and 0.1M sodium pyrophosphate plus 0.1M NaOH). The alkaline sodium pyrophosphate solution was found to be the most suitable because of both its extraction efficiency and the quality of the organic matter extracted which allows a good characterization of the stabilization degree attained by composting. Neutral sodium pyrophosphate extracts also show characteristic HI values for different samples but lower extraction efficiencies. The HI values for sodium hydroxide extracts show only little differences between manures and composts. The good correspondence found between HI data and isoelectric focusing (IEF) patterns confirmed on one side that humification indexes give a quantitative measure of the humification degree, on the other side that IEF is a suitable technique in order to obtain qualitative informations on organic matter stabilization in earthworm casts.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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