Incorporação de Resíduos Urbanos e as Propriedades Físico-Hídricas de um Latossolo Vermelho Amarelo. / Urban Residues Incorporation and Soil Physico-Hidric Properties of a Red Yellow Latosol

AUTOR(ES)
DATA DE PUBLICAÇÃO

1999

RESUMO

An experiment was carried out during two years on a Red Yellow Latosol cropped with sugar-cane, located in the country of Piracicaba-SP (22o41’00" S; 47o39’00" W; 554 m high). Nine treatments with 4 replications were used in a random-block experimental design. The treatments were: tr1 – mineral fertilization + CaCO3; tr2, tr3; tr4 and tr5 - levels of sewage sludge (respectively, 0; 33; 66 and 99 Mg ha-1, in the first year, and 0; 37; 74 and 112 Mg ha-1, in the second year); tr6, tr7; tr8 and tr9 - levels of composed of garbage (respectively, 0; 20; 40 and 60 Mg ha-1, in the first year, and 0; 24; 48 and 72 Mg ha-1, in the second year). The residues were manually applied on the soil surface and incorporated with a rotative plough. In the first year, the incorporation was done on the total area; in the second year only in inter-rows. The following soil parameters were determinated in each plot: particle size distribution (samples collected before the installation of the experiment); organic carbon content (15 samplings along the two years); natural clay content, soil bulk density and total soil porosity (sampling at the end of the first and second years of the growing cycle); water retention curves, saturated hydraulic conductivity and relative unsaturated hydraulic conductivity (samples collected at the end of the first year of the growing cycle); and saturated and unsaturated hydraulic conductivity (determined in situ at the end of the first and second years of the growing cycle, using tension infiltrometer). Results show a decrease the soil bulk density and increase of total porosity as the levels of residue application increased, for the 0 to 0.15 m soil layer, in the second year of application. On the plots that received applications of both residues, there was increase of the hydraulic conductivity near the soil saturation and decrease for the 0 to 1 kPa matric potential range. The decline of the relative hydraulic conductivity starting from the saturation, was initially more accentuated in the plots that received applications of both residues as compared with the ones that did not. It was also verified, through analyses of multiple regression, that differences in the water retention and in the natural clay content, that they would be attributed exclusively to the treatments by the conventional variance analysis, they were partially or totally owed to non casual variations in the particle size distribution of the soil. It could be concluded that the soil application of urban residues causes modifications of soil physical properties as saturated and unsaturated soil hydraulic conductivity. It could also be concluded that the randomization of the treatments in the experimental area does not guarantee the covariance absence between the treatments and other independent variables, which can interfere in the properties of interest (dependent variables) and, consequently, in the efficiency of the variance analysis done in a conventional way.

ASSUNTO(S)

densidade do solo sewage sludge water retention infiltrômetro de tensão porosidade do solo condutividade hidráulica do solo lodo de esgoto composto de lixo soil density tension infiltrometer soil porosity retenção de água soil hydraulic conductivity urban waste compost

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