Integrated agroforestry system affects the dynamics of inorganic phosphorus fractions in the savanna of Brazilian Northeast

The savanna (Cerrado) of northeastern Brazil has undergone significant transition in land use to expand agricultural activities. In this region, soils are highly weathered, with phosphorus (P) commonly bound to aluminum (Al) and iron (Fe), creating conditions that demand the supply of P fertilizers to build soil fertility. Conservation systems, such as integrated agroforestry, can increase the inorganic P lability. The aim of this study was to evaluate soil P availability in components of an integrated agroforestry system. Four systems were studied from a 3-year experiment: eucalyptus ( E. urophylla × E. tereticornis) rows (ER), sabiá ( Mimosa caesalpiniifolia) rows (SR), inter-planted maize, and inter-planted soybean in addition to an area of native Cerrado (NC) used as a control. Inter-planted soybean and maize components showed an increase in available P in relation to NC, as a response to a liming-induced increase in soil pH and phosphate fertilization. Eucalyptus and sabiá row components showed an increase in available P in soil because of higher P recycling promoted by forest species and lower P adsorption onto Fe and Al due to the high concentrations of organic matter. Phosphorus forms, following a descending order for all components of the agroforestry system, are P–Al > P–Fe > P–Ca. This information can be used to improve management and soil quality of agricultural production in the Cerrado of the Brazilian northeast region.