Estimation of Potential Nitrogen Mineralization From Class-B Centrifuge Cake Biosolids and Lagoon-Aged Air Dried Biosolids.

Beneficial use of biosolids through land application as a source of nutrients for growing crops is a very popular biosolids management option. One challenge in land application of biosolids as a nutrient source is predicting nitrogen (N) mineralization rates so that crop nutrient requirements are met with minimal potential for contamination of receiving waters from biosolids-derived N. We amended a field moist silty clay loam and a sandy soil adjusted to 80% field capacity water content with Class B centrifuge cake biosolids (fresh cake) and Class A lagoon aged air-dried biosolids (aged biosolids) obtained from the Calumet and Stickney Water Reclamation Plants of the Metropolitan Water Reclamation District of Greater Chicago at a rate of 18 Mg ha^-1. Milorganite biosolids were also used as a reference in addition to non-amended control soils. Biosolids-amended and non-amended control soils were incubated for 100 days at 20°C and periodically soil samples were removed and analyzed for 2 M KCl-extractable ammonia-N and nitrate-N. Nitrogen mineralization ranged from 28 to 37% of total N in the fresh cake and from 9 to 14% in the aged biosolids, depending on soil type and source of biosolids (Stickney or Calumet). Nitrogen mineralization in Milorganite ranged from 40 to 46%. The data showed that N mineralization in fresh cake is much higher than the rate used in calculating agronomic N rate for biosolids in Illinois and that N mineralization rate in aged biosolids is much lower than in the fresh cake.