Physical properties of a humic cambisol under tillage and cropping systems after twelve years

Soil is the basis underlying the food production chain and it is fundamental to improve and conserve its productive capacity. Imbalanced exploitation can degrade agricultural areas physical, chemical and biologically. The objective of this study was to evaluate some soil physical properties and their relation with organic carbon contents of a Humic Dystrudept under conventional tillage (CT) and no-tillage (NT), for 12 years in rotation (r) and succession (s) cropping systems. The experiment was carried out in Lages, SC (latitude 27 º 49 ' S and longitude 50 º 20 ' W, 937 m asl), using crop sequences of bean-fallow-maize-fallow-soybean in conventional tillage rotation; maize-fallow in conventional tillage succession; bean-oat-maize-turnip-soybean-vetch in no-tillage rotation; and maize-vetch in no-tillage succession. The experimental design was completely randomized with four replications. The soil samples were collected in the layers 0-2.5, 2.5-5, 5-10, and 10-20 cm. The following properties were analyzed: soil density, porosity, aggregate stability, degree of flocculation, water retention, infiltration, mechanical strength, and total organic carbon. Soil aggregation in the surface layer (0-5 cm) was better in the no-tillage than the conventional system, related to higher microporosity, organic carbon contents and water retention capacity, indicating that a periodical tillage of this soil is unnecessary. Infiltration was highest in no-tillage with crop succession. O solo é a base da cadeia produtiva de alimentos, por isso tornam-se necessárias a conservação e manutenção de sua capacidade produtiva. Muitas áreas exploradas de forma incorreta podem apresentar degradação física, química e biológica. O objetivo deste estudo foi avaliar alguns atributos físicos e suas relações com os teores de carbono orgânico de um Cambissolo Húmico alumínico nos sistemas de preparo convencional (PC) e semeadura direta (SD), após 12 anos com rotação (r) e sucessão (s) de culturas. O experimento foi conduzido em Lages - SC, situado a 27 º 49 ' de latitude sul e 50 º 20 ' de longitude oeste, com altitude média de 937 m. As sequências de cultivo foram: feijão-pousio-milho-pousio-soja no preparo convencional rotação; milho-pousio no preparo convencional sucessão; feijão-aveia-milho-nabo-soja-ervilhaca na semeadura direta rotação; e milho-ervilhaca na semeadura direta sucessão. O delineamento experimental foi inteiramente casualizado, com quatro repetições. As amostras de solo fora