1,721,037 research outputs found
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
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
Retention of coumaric-acid by soil and its colloidal components
No full textIn this study of the behavior of coumaric acid added to soil, the disappearance of the acid was found to be due to adsorption plus microbial degradation, and was influenced by the concentration and contact time. Adsorption experiments set up with soils varying widely in their chemical and physical properties, showed that the Freundlich isotherm fits the data quite well and that among the different soil factors, only the pH was closely and negatively correlated with coumaric acid adsorption. Approximately at pH > 7 no adsorption occurred, perhaps due to the repulsion between the negatively charged soil colloids and the dissociated acidic groups of coumaric acid. Adsorption experiments carried out with different adsorbents showed that the hydroxy-Fe compound was the most effective in retaining coumaric acid, followed by humic acid, illite, kaolinite and vermiculite, in this order.
In this study of the behavior of coumaric acid added to soil, the disappearance of the acid was found to be due to adsorption plus microbial degradation, and was influenced by the concentration and contact time. Adsorption experiments set up with soils varying widely in their chemical and physical properties, showed that the Freundlich isotherm fits the data quite well and that among the different soil factors, only the pH was closely and negatively correlated with coumaric acid adsorption. Approximately at pH > 7 no adsorption occurred, perhaps due to the repulsion between the negatively charged soil colloids and the dissociated acidic groups of coumaric acid. Adsorption experiments carried out with different adsorbents showed that the hydroxy-Fe compound was the most effective in retaining coumaric acid, followed by humic acid, illite, kaolinite and vermiculite, in this orde
Organic acids as seed germination inhibitors
No full textPhytotoxicity of aromatic and aliphatic acids was tested by a wheat seed bioassay. Wheat seed germination was found to be influenced by the number of hydroxy and methoxy groups, the molecular position of single and double hydroxy groups, the length of the aliphatic chain, as well as by the pK(a) of the acid solutions. Orto and meta coumaric, ferulic and orto hydroxybenzoic among phenolic acids, and butyric acid among aliphatic acids showed the most inhibitory activity; toxicity was found to increase exponentially with the increasing acid concentrations. levels of 0.25 and 1.8mM resulted in a 10 and 50% toxicity, respectively
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
No full text
- …
