Guedes, Rafael Silva creator Alleoni, Luís Reynaldo Ferracciú creator Correia, Benedito Luiz creator Alves, Luis Wagner Rodrigues creator Ramos, Sílvio Junio creator Fernandes, Antonio Rodrigues creator text periodical abstract or summary bl. continuing eng ABSTRACT: Due to the large extent of degraded areas in the Amazon, the use of conservation systems is very important to contain the advance of the agricultural frontier, and may favor the availability of nutrients such as phosphorus (P). This study evaluated effect of tillage systems on and cover plants distribution of organic P fractions (Po) in oxisol under soybean and grasses in crop successions. The experimental design was completely randomized with four replicates and five treatments: (i) conventional tillage (CT) with annual soil tillage; (ii) no-till (NT) in succession with Urochloa ruziziensis (NT1); (iii) NT in succession with U. brizantha (NT2); (iv) NT in succession with Panicum maximum (NT3); and (v) a control consisting of a fragment of native vegetation (NV). The Po fractions were quantified at depths of 0-5, 5-10, and 10-20 cm, before and after soybean cultivation and the P fractions were analyzed. The samples at a depth 0-5 and 5-10 cm had increased levels of biomass P in the NT1 and NT2. In addition, at depths of 0-5 and 5-10 cm, the treatments in no-tillage systems accumulated the most of the Po labile fractions. These results showed that conservation systems tend to accumulate most of the P fractions in soil through decomposition of organic residues. Thus, no-tillage system was shown to be important for Po supply, where the use of U. brizantha ‘Piatã’ (NT2) favored higher levels of organic P in labile and moderately labile fractions in soil, which was considered the best alternative for Po supply among the species tested. Key words: Glycine max, organic phosphorus fractionation, humic fractions, no-till. Publicação on-line; 43 ref.; 4 tables; Sumaries (En) SOJA GRAMÍNEA ANÁLISE DO SOLO SISTEMA DE CULTIVO AMAZÔNIA PLANTA DE COBERTURA Campinas-SP Instituto Agronômico - Coordenadoria da Pesquisa Agropecuária 1941 2024-4959 0006-8705 BR2025001025 v. 49 p. 434-446; (2020) https://www.scielo.br/j/brag/a/LpmjtN9mSswVdJdncWGSDvb/?format=pdf&lang=en https://www.scielo.br/j/brag/a/LpmjtN9mSswVdJdncWGSDvb/?format=pdf&lang=en BR-BrBNA 250508 20250508122623.0 eng