Physical-chemical characterization and comparison of digestion methods of organic residues / CaracterizaÃÃo fÃsico-quÃmica e comparaÃÃo de mÃtodos de digestÃo de resÃduos orgÃnicos

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

The use of residues in agriculture can be a viable alternative from the point of view of the environment and economics purposes. However, it is necessary characterize in an adequate way the different residues available, in order to establish correct application rate, improve use efficiency, and avoid environmental pollution. The objective of this work was to characterize the organic matrix and evaluate the different methods of digestion, using two samples mass, commonly used for chemical characterization of organic residues. Physical and chemical analyses were accomplished at the Department of Soil Science/UFLA. It was analyzed samples of sewage sludge, poultry manure, commercial compost, pig manure, quail manure, bovine manure, commercial organic substrate and commercial humic material with predominance of the humic acid. To evaluate the agronomic value, the samples were analyzed for: pH, electric conductivity, cation exchange capacity (CEC), concentration of N-total and N-mineral, organic matter (OM), total organic carbon (TOC) and the following fractions of the TOC: C-fraction humic acid (C-FHA); C- fraction fulvic acid (C-FFA), water soluble carbon (WSC), C-labile and concentration and types of low mass molecular organic acids. Two samples mass (100 and 200 mg) were used, in combination with four different organic residues digestion methods: 1) nitric-perchloric digestion (HNO3+HClO4); 2) aqua-regia digestion (HCl:HNO3, 3:1); 3) microwave digestion with nitric-acid; 4) dry ashing with solubilization of final extract with nitric-acid. The higher the C-humic acid fraction, the more elevated is the CEC of the organic residues. According to the humification index (HI), humification reason (HR) and the CEC, samples of pig manure, bovine manure, poultry manure, quail manure, organic compost and sludge sewage 1 could be classified as residues not completely humificated. The factor utilized to convert TOC to OM is different of that used for soils. Nitric-perchloric digestion method, in combination with 200 mg of sample mass, recovers the higher nutrients contents, for the majority of organic residues analyzed. The nitric-perchloric method, using 100 and 200 mg of sample mass, recovered the lowest levels of K, comparing to the others digestion methods tested. In this case, digestion method using aqua-regia and microwave are technically more adequate for quantifying K contents.

ASSUNTO(S)

resÃduo orgÃnico caracterizaÃÃo quÃmica mÃtodos de digestÃo organic residues chemical characterization ciencia do solo digestion methods

ACESSO AO ARTIGO

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