35 Ill. Adm. Code 391.412
Phosphorus
Section 391
Section 391.412 Phosphorus
a) The phosphorus content of the soil may govern loading rates
for the sludge. It is recommended that the available phosphorus content in
soils and total phosphorus in the sludge be analyzed every 2 years.
b) After five years of sludge application the phosphorus level in
the soil shall be monitored and sludge application shall cease if the plant
available phosphorus content in the soil exceeds 400 pounds per acre for sandy
soils or 800 pounds for non-sandy soils.