Wastewater disposal can be challenging for municipalities. Before the 1950s, wastewater was disposed of in bays, lakes, and rivers, which resulted in high levels of pollution [U.S. Environmental Protection Agency (USEPA), 1979]. In response to government regulations, alternative methods of processing and using municipal sewage have been developed. Specifically, methods have been developed to process sewage sludge from municipalities into a soil amendment, termed “biosolids.” The quality of the biosolids varies among municipalities because of incoming sewage, runoff water quality, and processing methods. Therefore, biosolids are graded based on strict safety requirements established by the USEPA in the 1970s. Regulated characteristics include pathogen content, the extent to which it attracts vectors (e.g., birds, insects, rodents, etc.), and the concentration of trace elements [e.g., arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), mercury (Hg), etc.], and nutrients. USEPA Grade A, exceptional quality (EQ) biosolids exceed all of these safety requirements and are cleared for most agricultural applications including use on edible crops with exception of all USDA-certified organic production. Grade B biosolids do not meet all of the safety requirements and are restricted in their use and access by the general public (Lu et al., 2012; USEPA, 1995).
Biosolids can be a valuable source of plant nutrients. In contrast with most conventional fertilizers, biosolids typically have lower levels of nitrogen (N), phosphorus (P), and potassium (K), but supply organic matter and micronutrients, such as boron, magnesium (Mg), Cu, and zinc (Zn) (Warman and Termeer, 2005). The ratio of N to P tends to be lower in composted biosolids because ≈15% of N is lost during the composting process through ammonia volatilization (Tubail et al., 2008). The application rate of biosolids is often limited by the concentration of P in the soils. Similar to land application of manures, repeated application of biosolids may result in soil P concentrations that exceed plant requirements (Lu et al., 2012). In addition, agricultural soil with excessive phosphorus can lead to P contamination of surface waters (Sharpley et al., 1993).
In the United States, ≈60% of biosolids are land applied, but less than 0.1% of agricultural lands are treated with biosolids annually (National Research Council, 2002; North East Biosolids and Residuals Association, 2007). About 40% of biosolids are typically disposed of in landfills. Almost no biosolids are land applied in the state of Mississippi, despite its potential use in agricultural, forestry, and horticultural landscapes. Two municipalities in Mississippi use a unique European system to produce Grade A, EQ biosolids (P. Fisher, personal communication). This is accomplished by placing pressed, dewatered, sewage solids into an enclosed greenhouse where the biosolids are aerobically digested under hot and humid conditions. Autonomous tillers continually turn the biosolids until the desired moisture content is achieved. At that point, the biosolids are removed from the greenhouse and tested for quality and contaminants. Although this soil amendment has been made available to the public for pick up, most of it has been disposed of at the landfill. Awareness of this product could increase demand, but the effects of biosolids from these municipalities on soil fertility in this region and on plant size have not been tested. The goal of this research is to measure the effectiveness of these biosolids as a fertilizer and soil amendment and compare their performance with conventional and slow-release fertilizers.
Espinoza, L., Slaton, N.A. & Mozaffari, M. 2013 Understanding the numbers on your soil test report. Univ. Arkansas Dept. Agr. Coop. Ext. Serv. FSA2118PD112RV
Franzluebbers, A.J. 2005 Soil organic carbon sequestration and agricultural greenhouse gas emissions in the southeastern USA Soil Tillage Res. 83 120 147
Funderburg, E. & Crouse, K.K. 1987 Procedures used by the Mississippi soil testing and plant analysis laboratory. Mississippi State Univ. Ext., Mississippi State University, Starkville, MS
Kidd, P.S., Domínquez-Rodríquez, M.J., Díez, J. & Monterroso, C. 2006 Bioavailability and plant accumulation of heavy metals and phosphorus in agricultural soils amended by long-term application of sewage sludge Chemosphere 66 1458 1467
Kolář, J. & Seňková, J. 2008 Reduction of mineral nutrient availability accelerates flowering of Arabidopsis thaliana J. Plant Physiol. 165 1601 1609
Marschner, H. 1995 Mineral nutrition of higher plants. 2nd ed. Academic Press, London, UK
McCracken, R.J. 1959 Certain properties of selected southeastern United States soils and mineralogical procedures for their study. Virginia Agr. Expt. Sta. Southern Regional Bul. 61
National Research Council 2002 Biosolids applied to land: Advancing standards and practices. Natl. Acad. Press, Washington, DC
North East Biosolids and Residuals Association 2007 A national biosolids regulation, quality, end use and disposal survey: Final report. North East Biosolids Assn., Tamworth, NH
Overstreet, L.F. & DeJong-Hughes, J. 2009 The importance of soil organic matter in cropping systems of the northern Great Plains. 28 Sept. 2017. <http://www.extension.umn.edu/agriculture/soils/soil-properties/importance-of-soil-organic-matter/>
Ozores-Hampton, M., Stansly, P.A. & Salame, T.P. 2011 Soil chemical, physical, and biological properties of a sandy soil subjected to long-term organic amendments J. Sustain. Agr. 55 245 259
Sharpley, A.N., Chapra, S.C., Wedepohl, R., Sims, J.T., Daniel, T.C. & Reddy, K.R. 1993 Managing agricultural phosphorus for protection of surface waters: Issues and options J. Environ. Qual. 23 437 451
Tubail, K., Chen, L., Michel, F.C. Jr, Keener, H.M., Rigot, J.F., Klingman, M., Kost, D. & Dick, W.A. 2008 Gypsum additions reduce ammonia nitrogen losses during composting of dairy manure and biosolids Compost Sci. Util. 16 285 293
U.S. Environmental Protection Agency 1979 A history of land application as a treatment alternative. U.S. Environ. Protection Agency Publ. MCD-40
U.S. Environmental Protection Agency 1995 Guide to the biosolids risk assessments for the EPA Part 503 Rule. U.S. Environ. Protection Agency Publ. EPA/832-B93-005
Wada, K.C., Yamada, M., Shiraya, T. & Takeno, K. 2010 Salicylic acid and the flowering gene FLOWERING LOCUS T homolog are involved in poor-nutrition stress-induced flowering of Pharbitis nil J. Plant Physiol. 167 447 452
Warman, P. & Termeer, W. 2005 Evaluation of sewage sludge, septic waste and sludge compost applications to corn and forage: Yields and N, P and K content of crops and soils Bioresour. Technol. 96 955 961