EFFECT OF CROPPING SYSTEMS ON SOIL CHEMICAL CHARACTERISTICS, WITH EMPHASIS ON SOIL ACIDIFICATION

The soil under intensive cultivation and low addition of crop residues is exposed to erosion and reduction of organic matter. Increases in s oil organic matter, cation exchange capacity (CEC) and nutrient availa bility may occur in no-till systems with legumes and with large additi ons of organic residues. Nevertheless, some legumes may increase soil acidification through the carbon and nitrogen cycles. An experiment wa s carried out over 10 years, with 10 cropping systems on a Dark Red Po dzolic soil (Paleudult) to evaluate the effect of no-till cropping sys tems on soil chemical characteristics. Legume cropping systems resulte d in the greatest soil organic C gain and the highest ECEC to a depth of 17.5 cm. The increase was greatest at 0 - 2.5 cm layer. Clover syst ems resulted in the highest soil acidification at 2.5 - 7.5 and 7.5 - 17.5 cm depths. The rate of soil pH decrease at 2.5 - 7.5 cm depth und er clover+ Spergula/maize system was 0.1 unit year(-1). Differences in soil acidification affected soil ECEC. Soil exchangeable cation data indicate that nitrate leaching increased soil acidification. Maize yie lds were greatest in legume systems due to increased N supply.