Biochemical origin and refractory properties of humic acid extracted from the maize plant

Humic acids (HA) contribute to soil fertility because of their chemical, physical, and biological properties. The origin of HAs in soils has puzzled scientists for decades, and what HAs are and what their origin is remain unclear. The isolation of HAs in plants, which have characteristics close to soil HAs, suggests the probable origin of soil-HA is the preservation of plant tissue, indicating biochemical origin. In this paper HA from maize plant at different stages of maturity is isolated, from which it was found that the evolution of this fraction depends on and is derived from cell wall formation. Evidence was also found that HA was above all composed of lignin and cutin residues, and was characterized by low surface area. After 8 months of incubation in both mineral-artificial and natural soils, humic acid isolated form maize plant could be recovered intact

Organic matter evolution during co-composting of the organic fraction of municipal waste and poultry manure

The study concerned the evolution of organic matter, and the humification process, during the co-composting of the organic fraction of municipal solid waste (OMSW) and poultry manure (PM); the study was made with two different mixtures (OMSW:PM ratios of 3:2 and 2:3, wet weight:wet weight) and two different particle sizes (1 and 0.2 cm). The results suggested that the composting process proceeded unhindered throughout the degradation of easily degradable materials like hemicellulose, and that of the rather less degradable cellulose and lipids, and the concentration of recalcitrant material, i.e. a ligno-humic (LU) fraction. These processes were more evident for mixtures with lower particle size. Throughout the composting, in all mixtures studied, humification proceeded by the formation of a new HA fraction, which was probably the result of the partial degradation and solubilization of more complex insoluble organic molecules, i.e. humin fraction. (copyright) 2005 Elsevier Ltd. All rights reserved

Precision determination for the specific oxygen uptake rate (SOUR) method used for biological stability evaluation of compost and biostabilized products

This work represents the first attempt to evaluate the precision of the specific oxygen uptake rate method expressed in terms of repeatability (r) and reproducibility limits (R). Three laboratories were involved in an inter-laboratory test for the validation of respiration analyses on six biomass samples (three composts and three biostabilized products) having different degrees of biological stability. Both the maximum specific oxygen uptake rate peak (SOUR) and the cumulative oxygen demand after 12h (OD(12)) and 20h (OD(20)) of respiration test were investigated. Precisions expressed as the relative standard deviation were in the range of 9-41%. Linear regressions found for r and R, versus OD(12) and OD(20), enabled derivation of precision values (r and R) for all respirometric levels within the operating range. The OD(12) and OD(20) indices were found to be more adequate to indicate biological stability since they were less influenced by random errors than the SOUR index

Nanometer scale structure of alkali-soluble bio-macromolecules of maize plant residues explains their recalcitrance in soil

The quantity and the quality of plant litter returned to the soil play an important role in the soil organic matter balance. Besides other pedo-climatic aspects, the recalcitrant molecules content of plant residue and theirs chemical composition play a main role in determining plant residue preservation. In this study we report that intrinsically resistant alkali-soluble bio-macromolecules extracted from maize plant (plant-humic acid) (plant-HA) contribute directly to the soil organic matter by just addition and conservation in the soil, and that a high syringyl/guaiacyl (S/G) ratio in the lignin residues composing plant tissue, modifying the microscopic structure of the plant alkali-soluble biopolymers enhances theirs recalcitrance because of lower accessibility of molecules to degrading enzymes. These results suggested in agreement with more recent literature that humic substance of soil consist of mixture of identifiable biopolymers coming directly from plant tissue that are added annually by maize plan residue

Clinical investigation of cognitive styles in patients with acquired brain damage.

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Precision determination for the specific oxygen uptake rate (SOUR) method used for biological stability evaluation of compost and biostabilized products

Abstract Test validation needs to assure results quality when new methods are proposed as routinely matter. This work represents a first attempt to validate the Specific oxygen uptake rate method (SOUR) by precision, i.e. repeatability (r) and reproducibility limits (R), detection. Three laboratories were implied in an inter-laboratories test for respirometric analysis by SOUR on six biomasses (3 composts and 3 biostabilized) of different degree of biological stability. Both maximum specific oxygen uptake rate (SOUR peak) and cumulative data registered for 12 h (OD12) and 20 h (OD20) were investigated. Precision values expressed as relative standard deviation, were in the range of 9 and 41%. Linear regressions found for r and R, versus OD12 and OD20 allowed deriving precision values (r and R) for all levels contained in the operating range. OD12 and OD20 indexes seemed to be preferred to indicate biological stability as they are less influenced by random errors than SOUR index