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Water extracts of fresh and mature farmyard manure
No full textWater extracts of fresh and 3-month stabilized FYM were examined. The maturation process produced a significant increase in the water-soluble dry matter, organic C and N, pH and EC. No significant difference was found in phenol content, whereas spectroscopic measurements of the extract indicated a higher condensation of organic components with the ageing of the materials. Germination index values, higher in the mature samples, show the persistence in nearly all samples of long-lasting toxicity. Molecular weight distribution in water extract shifts markedly to the high molecular weight side as the stabilization occurs
Carbon mineralization kinetics as influenced by soil properties
No full textIn a short-term laboratory study C mineralization potentials were determined on soil samples obtained from some representative agricultural soils in Tuscany, Italy. All the kinetic models tested to describe the mineralization process provided a good fit to the experimental data. A modified first-order model best described C mineralization in the soil. Both potentially mineralizable C and the mineralization rate (k) varied considerably among soils, reflecting the differences in soil properties. Potentially mineralizable C was positively related to C evolved as CO2 and to the exchange capacity. Normalized values (potentially mineralizable C divided by organic C), representing on average about 2% of the total soil C, was positively correlated to soil pH and negatively to the soil C pool, the soil N pool, and total microbial activity. Values for k ranged between 0.050 and 0.104 day-1, being higher in fine-textured soils and in soils with a large free Fe content. A low C:N ratio was indicative of a high k value. Turnover times for mineralized C were relatively rapid, ranging from 10 to 20 days
Maturity evaluation of organic wastes
No full textIt seems to be possible to evaluate chemical stabilization of organic wastes on the basis of various humification indexes determined in the laboratory, i.e., a place in which controls can be applied more rigorously than in the field. Among the parameters tested, the HI seems to be the most appropriate, even though it is less simple and rapid. Before defining which among the parameters is the most suitable for evaluating the degree of maturity of organic wastes and utility in crop production, a much greater number of wastes of the same kind but composed under different conditions must be tested.
Among the chemical criteria required for the characterization of an organic waste stabilization product (e. g. , compost), humus content and quality rank high. This aspect was investigated by several authors each following a different experimental approach. The objectives of the present study were to attempt to follow the course of the maturation process in composting through the use of various humification parameters; and to evaluate suitability of the parameters for statistically assessing the maturity of different organic wastes
Effetto dello spandimento delle acque reflue dei frantoi oleari su alcune proprietà del terreno agrario
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Carbon mineralization in soil amended with different organic materials
No full textLaboratory incubation experiments were conducted (for 21 days) to determine the rate and extent of decomposition of 3 animal wastes (farmyard manure, pig slurry and poultry manure), 2 urban wastes (sewage sludge and municipal refuse compost) and one crop residue (rye straw) in a sandy loam soil. The extent of amendment decomposition was found to be a power function of time, related to the incubation temperature and chemical composition of the organic material. The different rates of application used, revealed the pronounced effect of straw on loss of native soil carbon. Farmyard manure and municipal refuse compost were found to be the materials most resistant to short-term decomposition
Mineralization parameters from organic materials added to soil as a function of their chemical composition
No full textCarbon mineralization of different organic materials added to soil was monitored over a short time in a laboratory incubation experiment. Several kinetic models were evaluated for their suitability in describing the decomposition processes. A modified first-order model best described carbon mineralization for each material. Parameters derived from such a model were tested as indexes for assessing the relationships between the decomposition in soil of the organic materials and their chemical compositions. The term 'initial potential rate of C mineralization', especially when normalized to total C added to soil, was found to be the most effective index for assessing the above-mentioned relationship.
Carbon mineralization of different organic materials added to soil was monitored over a short time in a laboratory incubation experiment. Several kinetic models were evaluated for their suitability in describing the decomposition processes. A modified first-order model best described carbon mineralization for each material. Parameters derived from such a model were tested as indexes for assessing the relationships between the decomposition in soil of the organic materials and their chemical compositions. The term 'initial potential rate of C mineralization', especially when normalized to total C added to soil, was found to be the most effective index for assessing the above-mentioned relationship
The effect of forty years of continuous corn cropping on soil organic matter characteristics
No full textChanges in humus and some of the major extractable components of soil organic matter were examined, following forty years of conventionally tilled continuous corn cropping compared with those of an adjacent untilled native grassland soil. Results indicate that long-term continuous cropping caused a significant reduction in the content of alkali extractable and water soluble carbon, as well as in the phenolic and chloroform extractable compounds, while no differences in volatile acids and n-hexane extractable substances were found. On the basis of organic C, corn cropping led to a relative enrichement of phenolic compounds, volatile acids and substances extractable by Na4P2O7, but it did not affect the substances extractable by water. Except for the humification ratio (HR), the humification parameters, such as humification degree (HD), the extracted humic and fulvic acids, the C(HA)/C(FA) ratio and the humification index (HI) revealed a higher degree of humification of the organic matter in native grassland than in the continuous corn cropping system. IR spectra of n-hexane, chloroform, alkaline and water extracts failed to show significant differences between sites under native grassland and sites under continuous corn
Soil quality under the energetic crop giant reed (Arundo donax L.), cropping sequence and natural grassland
No full textThe objective of this study was to determine, on the same pedological, topographic and climatic conditions, the effect of a continuous giant reed cropping (GR), a cropping sequence (CS) as well as of untilled native grassland (NG) on some soil quality characteristics. Between the examined parameters, total soil organic carbon (TOC), light fraction carbon (LFC), dissolved organic carbon (DOC) cumulative mineralized carbon (Cm), microbial biomass carbon (MBC), basal respiration, metabolic quotient (qCO2), potentially mineralizable carbon (C0), dehydrogenase (DHA), catalase (CA) and ß-glucosidase (GL) activities, as well as fluorescein diacetate hydrolysis (FDA), biological index of fertility (BIF) and initial potential rate of carbon mineralization (C0•k), were higher in the continuos giant reed cropping than in the cropping sequence. The C mineralization rate (k) was lower in GR than in CS, while the metabilc potential (MP) was similar in the two sites.
For what concerns the difference between GR and NG, this last usually considered as a reference or base line in evaluating attributes of soil quality, GR showed higher values for TOC, LFC, DOC and catalase activity. TOC and catalase, also for their analytical semplicity, may be suggested as the most suitable soil biochemical indicators for differentiating the effects of different crop management systems
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