Impacts of biosolids application on soil quality under alternate year no-till corn-soybean rotation

Biosolids are a source of recycled organic matter and nutrients. To evaluate the impact of biosolids application (1984-2008) on soil quality, composite soils (Genesee silt loam, fine loamy, mixed, nonacid, and mesic typic udifluvent) were randomly sampled at geo-referenced sites from 0 (control), 2, 5, and 25 years of lime-stabilized anaerobically digested biosolid- applied fields. Results showed that microbial biomass C( Cmic), N (Nmic), and P (Pmic) contents were signifi- cantly higher at both depths of the 5 and 25 years of biosolid-appliedfieldscomparedtothecontrol.Biosolid application significantly enlarged the biologically labile C( Cmic over total organic C, Cmic:Corg )a nd N( Nmic overtotalN,Nmic:TN)poolswithanassociateddecrease in metabolic C loss (20-53 %) by specific maintenance respiration (qCO2) relative to the control. The Corg, active (AC) and soluble C (SC), TN and reactive N (RN), and reactive P (RP) contents were significantly higher in the long-term biosolid-applied fields than in the control. However, there was an indication of leaching of SC, RN, and RP between depths. Years of biosolidapplicationsignificantlyincreasedsoilmoisture content (θv at −0.03 MPa) by 20-40 %, macroaggregate stability (MaA) by 2-44 %, and mean weight diameter (MWD) of aggregates by 7-51 %, respectively. Conse- quently, there was a decrease in soil bulk density (ρb) and microaggregate stability (MiA) at both depths. Re- sults confirmed that biosolids application at rates rec- ommended is a viable management option to improve soil quality for crop production. However, long-term and repeated biosolid applications above the recom- mended agronomic N and P rates may be responsible for accumulation and consequent leaching and runoff of SC,RN,and RP tocause groundwaterandsurface water pollution with environmental consequences.