High Quality Biosolids: Assessment of Nitrogen Mineralization and Potential for Improving Highway Soils

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Zhu, Chenglin
Felton, Gary K
Biosolids production is increasing with increase in human population. Over the years, the quality of biosolids has been improving with the upgrading of most wastewater treatment plants (WWTP) as dictated by a need to meet discharge limits in receiving water bodies. Applying biosolids to agricultural soils to improve crop production has been practiced for decades. With increased regulation on land application in agricultural lands, biosolids industry has been exploring ways to use biosolids in specific situations such as highway roadside soils to improve soil properties. Roadside soils are known to be compacted and contaminated due to vehicular traffic and typically have low organic matter and nutrients. The objective of this study was to investigate the efficacy of high quality biosolids (i.e. Bloom) to improve soil physical and chemical properties. Results showed that Bloom and its mixture can significantly improve soil bulk density and hydraulic conductivity. Bloom-amended soils had a higher nitrogen mineralization rate than the control (2.45 times faster in simulated roadside soil and 1.21 times faster in agricultural soil) and compost amended soil. Further, soils amended with cured Bloom had relatively slower N mineralization than those applied with uncured Bloom since the curing process will decrease organic matter (OM) content and facilitate the loss of N as ammonium. The take home message is that bloom is more effective than inorganic fertilizer in terms of improving soil physical properties for roadside soils and bloom mixed with sand and sawdust is more effective than pure bloom. Bloom addition can significantly increase soil organic nitrogen mineralization. Further study and analysis will be needed to conclude on the effect of deer compost on soil physical properties and the mineralization rate of Orgro amended soil.