LES EFFETS DE LA MISE EN CULTURE ET DE LA PRAIRIE PROLONGEE SUR LE CARBONE, L'AZOTE ET LA STRUCTURE DE QUELQUES SOLS DU QUEBEC

Abstract

The effects of cultivation (cultivated vs. non-cultivated soils) and the age of cultivated meadows (from 5 to 25 yr) on the evolution of carbon, nitrogen and soil structure were studied on some Quebec soils. The soil series used were Beaurivage, Charlevoix, Greensboro and Kamouraska which are important agricultural soils for Eastern Quebec. The air- and water-stability of soil aggregates were used to characterize the soil structure. As a result of cultivation, the Kamouraska soil lost 33% of the carbon and 8% of the nitrogen originally present in the virgin soil, while the decrease in the water-stable aggregates was 84%. Charlevoix and Greensboro soils showed losses varying from 30 to 35% for carbon and from 21 to 31% for nitrogen while the water-stable aggregates decreased by 50%. Under continuous meadow for 25 yr, the Kamouraska soil showed an increase of up to 36% for carbon and 64% for nitrogen whereas the Beaurivage soil did not show much variation. Such a cultural practice improved the soil structure mainly in the Kamouraska soil, as a result of the increase not only in carbon content but likely in the root biomass with time.