Resumo

RODRIGUEZ, Belkis; ESPANA, Mingrelia  e  CABRERA DE BISBAL, Evelyn. Propiedades químico-estructurales de la materia orgánica del suelo en un agro sistema de los llanos centrales venezolanos bajo diferentes prácticas de manejo. INCI [online]. 2004, vol.29, n.8, pp.461-467. ISSN 0378-1844.

Land use and agricultural management cause differences in the structure and composition of soil organic matter (SOM). The relative abundance of volatile organic products was determined to evaluate chemical-structural properties of SOM under different agronomical practices: conventional tillage (CT), no tillage (NT), no tillage with previous chisel (ChNT), maintenance (MR) and export of crop residues (ER), continuous maize (M-M) and maize-soybean cropping (M-S). The experiment was carried out on a Typic Hapluster Af soil, in the Central Llanos (9º23'33''N and 66º38'30''W), Venezuela. The chemical structural composition of SOM was measured by a degradative technique of pyrolysis gas chromatography (Py Gc) in soils and extracts. Individual treatments did not result in different SOM structures. The products were characterized by a high degree of humified and biologically altered compounds. In MRM-S and ERM-M the organic matter was enriched in material resistant to biodegradation. MR showed the least SOM humification and mineralization indexes under these conditions. The reduction of furfural, acetic acid and phenol at 20 days after harvest (dah), like to pyrrole at 35dah reflected to a considerable high rate of biodegradation of SOM in the 20dah. The lowest value of mineralization index was found in the NTMRM-M combination, while the structure of humic substances from soil extracts indicated no difference for NTMRM-M, ChNTMRM-M and CTMRM-M.

Palavras-chave : Labranza; Maíz; Materia Orgánica del Suelo; Pirólisis; Suelo.