Fig. 1. The 0- to 20-cm mean (n = 4) soil (A) oxalate-extractable Al, (B) oxalate-extractable Fe, (C) oxalate-extractable P, and (D) oxalate-extractable–based phosphorus saturation index (PSI_ox) from biosolids plots amended with 0, 6.7, 13, 27, or 40 Mg ha^–1 biosolids. The 0, 6.7, 13, and 27 Mg ha^–1 biosolids rates were applied in 1982, 1984, 1986, 1988, 1990, 1992, 1994, 1996, 2000, and 2002. The 40 Mg ha^–1 biosolids rate was applied at 6.7 Mg ha^–1 in 1982 and at 40 Mg ha^–1 in 1984, 1986, 1988, and 1990. Above the bars, same letters are not significantly different at = 0.05, determined by Fisher's Protected LSD. Error bars represent 1 SE of the mean.