Land-Use Change Enhances Organic Phosphorus Pools in Oxisols in Brazil's New Agricultural Frontier

Abstract

Land-use types and management systems can affect the availability of phosphorus (P) by modifying its compartments. The aim of this study was to evaluate the organic and inorganic fractions of P in an Oxisol in the Cerrado region of Brazil, considering various land-use types and management systems and the period of application. Nine different land-use types and management systems were evaluated in the district of Uruçuí, in the Cerrado region of the state of Piauí: no-tillage (NT3 and NT6, under cultivation for 3 and 6 years, respectively), pasture (PA2 and PA6, under cultivation for 2 and 6 years, respectively), eucalyptus (EU6 and EU12, under cultivation for 6 and 12 years), conventional tillage (CT2 and CT8, under cultivation for 2 and 8 years) and native Cerrado (NV), representing a balanced system. Sequential P fractionation was carried out on soils collected at depths of 0–0.1, 0.1–0.2, 0.2–0.3 and 0.3–0.4 m, resulting in organic and inorganic P fractions of different availability (Hedley sequential fractionation). Across most systems and depths, organic P (Po) predominated over inorganic P (Pi), especially in the labile and moderately labile pools. Pasture systems (PA2 and PA6) showed the highest levels of biological P, reaching 762 mg dm−3 in PA6, with biological P representing 82% and 85% (average of both PA2 and PA6) of the labile and moderately labile P pools, respectively. No-tillage and eucalyptus systems also accumulated significant Po in moderately labile fractions, indicating that conservationist systems promote long-term P stabilisation. Conversely, conventional tillage reduced total and recalcitrant P pools, highlighting its unsustainable nature. These findings suggest that land management practices promoting organic matter inputs and nutrient cycling enhance P retention and efficiency, contributing to sustainable agriculture in the MATOPIBA region.