EFFETS DU SOUS-SOLAGE ET DU LABOUR PROFOND SUR LES PROPRIETES PHYSIQUES DU SOL ET LE RENDEMENT DE LA LUZERNE ET DU MAIS SUR LOAM SABLEUX CHALOUPE

Following deep plowing and subsoiling treatment in 1971, alfalfa and corn silage were grown continuously during a 5-yr period on Chaloupe soils which have an indurated layer at 40 cm or deeper. These soils were formed from laminated particles of very fine sand and loam of recent sedimentary origin. Measurements taken in 1972 and 1975 included bulk density, resistance to penetration, permeability, organic matter content and soil texture. Subsoiling did not significantly change soil physical properties; only a slice of soilless than 10 cm wide at depth 50 cm and deeper on each side of and in the furrow made by the ripper showed modifications, without affecting crop yields. Deep plowing, however, in turning the soil by 120° to 150° resulted in redistribution of the organic matter and the soil texture down the profile, a diminution in resistance to penetration in the subsoil. But it did not change the porosity or the permeability of the lower layers. Physical modifications brought by deep plowing were still persistent after more than a 3-yr period. Improvement in physical and hydrodynamic soil properties following deep plowing did not have any beneficial effect on corn and alfalfa yields.