Phosphorus (P) is considered the most expensive and limiting nutrient for agricultural production in the tropics, due to the limitations of phosphate reserves and adsorption phenomenon. In the Amazon agricultural production may be limited by 90% due to P deficiency. In recent decades the introduction of monocutives, such as oil palm (Elaeis guineensis) in the state of Pará, has caused changes in land use, affecting nutrient availability and environmental dynamics. In this context, the insertion of oil palm into an alternative soil management model and conservationists such as the Agroforestry System (AS), can help reduce dependence on imported P, ensure greater use of P in the soil through organic sources and increase plant uptake through arbuscular mycorrhizae symbiosis. However, there is little information on the contribution of AS to P availability and mycorrhizal colonization in perennial crops like an oil palm in tropical agrosystems, especially in the Amazon. The aim of this study was to evaluate the labile and moderately P (organic and inorganic) fractions in soil and arbuscular mycorrhizal colonization in oil palm planted in biodiverse and monoculture agroforestry systems in the Brazilian Amazon. The P fractions were determined by sequential extraction method described by Hedley and mycorrhizal colonization was evaluated by intersection magnification method. Mycorrhizal colonization was generally 3.5 times higher in oil palm cultivated in Agroforestry in relation to monoculture and Agroforestry did not differ from monoculture in the supply of labile P and have a larger pool of moderately labile P in the soil. The results of the study showed that the adoption of Agroforestry Systems in oil palm cultivation in the Amazon is a promising practice to increase mycorrhizal colonization in this species and represents a type of advantageous management for the supply of available P and for the maintenance of P reserves compared to monoculture.
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