Caractérisation de l'espace poral d'un sol argileux: effets de ses constituants et du travail du sol

Abstract

The objective of this study was to compare the effects of three tillage treatments and soil constituents on soil porosity characteristics. The experiment was initiated in the fall of 1987 on a Kamouraska clay (Orthic Humic Gleysol). Moldboard plowing, chisel plowing and no-till were compared during the fourth growing season of a continuous barley (Hordeum vulgare L.) system. Surface soil samples were taken in late May 1991 after seeding and at the beginning of October before primary tillage. Soil porosity was characterized by measuring the total porosity and its textural, structural and shrinkage components. The tillage treatments had no significant effect on total porosity. In May, however, the structural porosity was 25% larger under moldboard plowing than under no-till. On average for the two sampling dates, the interclod porosity was 51% larger under moldboard plowing than under no-till. In addition, this component of the structural porosity increased during the growing season under all treatments. In May, the shrinkage porosity decreased progressively from moldboard plowing to chisel and to no-till whereas the reverse trend was observed in the fall. Textural porosity was positively correlated with clay and organic carbon contents. This study shows that tillage affects mainly the structural porosity and in particular its interclod and shrinkage components. Key words: Tillage, total porosity, structural porosity, textural porosity, shrinkage porosity