State Water Resources Research Institute Program


Project Id: 2010NC149B
Title: Mineralization, Plant Availability, and Water Quality Consequences of Nitrogen and Phosphorus in Land-Applied Municipal Biosolids
Project Type: Research
Start Date: 3/01/2010
End Date: 2/28/2011
Congressional District: NC 02
Focus Categories: Wastewater, Nutrients, Non Point Pollution
Keywords: biosolids, mineralization, nitrogen, phosphorus, land application, water quality
Principal Investigators: White, Jeffrey G; Hardy, David H.; Israel, Daniel; Lindbo, David L; Osmond, Deanna
Federal Funds: $ 38,000
Non-Federal Matching Funds: $ 32,720
Abstract: The ultimate goal of this project is to develop improved nitrogen (N) and phosphorus (P)availability coefficients that are needed to determine agronomically appropriate rates for application of different types of municipal biosolids to different receiver crops growing on North Carolina's diverse soils. Biosolids are the largely organic solids, semisolids, or liquid suspensions generated via treatment plant processing of municipal wastewater. Wastewater solids are first processed into sludge which receives additional treatment to produce biosolids for application to agricultural and forest lands and reclamation sites. As North Carolina's population continues to increase, our wastewater treatment plants generate ever-increasing quantities of biosolids, the majority of which are recycled via application to agricultural land. Biosolids are valuable sources of organic matter, which can improve soil chemical and physical properties for crop growth, and of nutrients, especially N and P, to fertilize crops. The majority of biosolids N is in organic forms that need to be mineralized into plant-available N (PAN: nitrate + ammonium) prior to plant uptake. Biosolids P is largely inorganic and may become unavailable after contact with soil; biosolids organic P requires mineralization to permit uptake. Research is needed to determine the biosolids N and P mineralization-availability coefficients required to determine appropriate rates of biosolids to apply to North Carolina agricultural lands. This will optimize crop nutrient uptake efficiency and minimize the quantities of excess N and P available to potentially contaminate ground and surface waters, thus protecting North Carolina water quality.

The specific objectives of this project are to:

  1. Evaluate several biological incubations and chemical analyses for their ability to estimate and predict N and P availability from several types of municipal biosolids in several representative receiving soils with a range of chemical and physical properties;
  2. Conduct short term greenhouse experiments to determine N and P and other nutrient and heavy metal uptake by representative receiving crops (bermudagrass, fescue, corn) from contrasting biosolids applied at several rates to several representative receiving soils with contrasting chemical and physical characteristics;
  3. Initiate field trials to determine N and P and other nutrient and heavy metal uptake by representative receiver crops (fescue, bermudagrass, corn) from contrasting biosolids applied at several rates to several representative receiving soils with contrasting chemical and physical characteristics. (An objective in subsequent years will be to develop laboratory, greenhouse, and field-based estimates of plant-available N and P for the second and third years after biosolids applications both in plots receiving biosolids only in the first year as well as those receiving biosolids in the second and third years.);
  4. Analyze and interpret the results from the three-pronged research effort outlined above in order to develop improved N and P mineralization-availability coefficients to be used to guide N and P rate determinations for land application of different biosolids on different soils for different receiver crops, with N rates based on realistic yield expectations for N, and P rates guided by the Phosphorus Loss Assessment Tool determination of P pollution risk.
  5. Use the information gleaned from this three pronged approach to estimate potential improvements in N- and P-use efficiency which will translate into less excess N and P available to contaminate ground and surface waters;
  6. Examine relationships between the laboratory analyses, greenhouse trials, and field trials with respect to the plant availability and uptake of heavy metals from the various biosolids on the various soils.
Progress/Completion Report, 2010, PDF

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