Phosphorus availability in sites archeological black earth in Oriximiná, Brazil

Abstract

Most of the Amazonian soils are generally acidic, with low cation exchange capacity and low fertility, which makes them limiting for increasing productivity and sustainability of agricultural systems in this region. Because of this, many family farmers are using archeological black earth (ABE) areas for their crops, as these have high levels of nutrients, mainly phosphorus (P). In this sense, the objective in the work was to analyze the availability of P in the soils of five archaeological sites in the Municipality of Oriximiná, Brazil. ABE samples were evaluated at depths 0-0.20 and 0.20-0.40 m from the archaeological sites (Maracajá, Faissal, Praia, Juquirizinhos I and II). The levels of available P were high, ranging from 4 to 304 mg kg^-1. The archeological site that had the highest average content was Juquirizinho I, ranging from 17 to 202 mg kg^{- 1} P and the one with the lowest average content was Praia, ranging from 5 to 20 mg kg^-1 of P. There was great variation in the levels of P between the sites, with emphasis on Juquirizinho I, which presented values between 17 to 202 mg kg^-1. Four of the five sites evaluated showed high availability of P, but some areas sampled showed values below 30 mg kg^-1, in this sense, they did not present an anthropic A horizon. There was a great variation in the levels of phosphorus in depth, considering the same archaeological site.