Physical Quality and Porosity Aspects of Amazon Anthropogenic Soils under Different Management Systems

Archaeological Dark Earth (ADE) soils are rich in organic matter and highly fertile, but when used for farming or grazing activities, they generally lose chemical and physical quality, becoming more susceptible to erosion. In this context, this study aimed to evaluate the changes in physical properties of the soil in different management systems adopted in ADE areas of the Amazon. The study area is located in the municipality of Novo Aripuanã, in the mesoregion of Madeira, south of the state of Amazonas. Three ADE areas were selected: 1—native forest (Amazon forest fragment); 2—area covered with Brachiaria (Urochloa brizantha cv. Marandu), without the addition of fertilizers or soil improvers; and 3—area covered with pigeon pea (Cajanus cajan) and other commercial crops (corn, beans, and watermelon). The following soil characteristics were evaluated: soil resistance to penetration, soil bulk density, macroporosity and microporosity, and total soil porosity in the 0–0.20 m and 0.20–0.40 m layers. The results showed that the pasture area presented a smaller amount of total pores and complex pores, which are important for water flow in the soil. The areas analyzed in this study presented no critical obstacle to plant root development with the low value of resistance to penetration (<2.00 MPa) in all areas.