Fig. 2. The molar ratio of P_ox/[Al+Fe]_ox (i.e., plotted against P_w of the soil samples taken from various depths of the control, pig slurry, poultry manure, and poultry manure mixed with litter treatments. The data points represented by the filled symbols (i.e., the samples from the 0- to 5- and 5- to 10-cm soil layers of the poultry manure and poultry manure mixed with litter treatments) were not included in calculating the Langmuir equation, because of these soil samples exceeded the theoretical maximum of 0.4 to 0.6.