The prediction of trace elements plant availability in biosolid-treated soils by extractants in a single extraction is seldom achieved and depends on the soil and biosolid properties, as well as the plant and environmental factors, such as temperature, humidity, and light. The method of trace elements extraction proposed in this work tries to mimic the rhizosphere environment by using both mono and divalent ions, different organic acid composition and several successive extraction kinetics to assess the total trace element “availability” that should be achieved after several plant growths in the same spot until that “available” fraction is depleted. The plots were fitted with the first order kinetic model and the kinetic parameters for Zn, Cd, Ni, Cr, and Cu were compared. The Zn ultimate metal release (Co) values due to the first order dissolution reaction from the 1, 10, and 100 mM complete organic acid solution (COAS) presented the same magnitude. The more appropriated extraction method was found to be the use of one and a half-grams of soil in 30 mL of 0.1 M of a modified organic acid solution (MOAS), pH 4.8±0.1, performing 15 successive extractions, each one every 24 hours.
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