Fig. 1. Effects of Al (Al-WTR) and Fe (Fe-BP) mineral by-products (A) and composting (B) on the distribution of P fractions in poultry manure. Treatment means for each extracted P fraction (DRP, FEP, CBDP, and H₂SO₄–P) followed by the same letter are not significantly different at the 0.05 level of probability. DRP = dissolved reactive P; FEP = 0.5 M NH₄F–extractable P; SHEP = 0.1 M NaOH–extractable P; CBDP = citrate–bicarbonate–dithionite extractable P; and H₂SO₄–P = 0.25 M H₂SO₄–extractable P.