Fig. 3. Relationship between water soluble P (WSP) or Mehlich-3 P (M3P) in the surface 5-cm layer of soil and dissolved reactive P (DRP) in runoff. Values are the average of four replications ± SE. CTL, control; CF, commercial fertilizer; PL, poultry litter; PLC, poultry litter-yard waste compost; BSC, biosolids compost.