Accumulation of organic matter in soils is an important strategy to improve both soil and environmental quality. We evaluated the medium-term effect (5-yr) of four maize cropping systems [maize: M; M+Canavalia ensiformes; M+Cajanus cajan; M+Stizolobium niveum; and M+Glicine sp] on the stocks of organic carbon (OC) and total nitrogen (TN) on a southern Brazilian Oxisol under reduced tillage. The previous soil cultivation during 23-yr under conventional tillage determined a decrease on soil organic matter stocks equivalent to 50-60% of the stocks in the adjacent native forest soil. In comparison with maize system, legume based maize cropping systems resulted in accumulation rates from 0.39 to 2.23Mg ha¹yr¹ of OC, and from 0.15 to 0.22Mg ha¹yr¹ of TN. In addition to environmental benefits of carbon sequestration in soils, the increase of soil organic matter contributed to increase of the cation exchange capacity, which represents an important improvement on the quality of this low activity clay soil.
Soil organic matter; cover crops; soil quality
