Evaluation of dredge fines material in manufactured soil blends on soil health parameters

Solutions are needed to address increasing concerns over degraded land and global food insecurity. One solution is to design soil blends that can restore soil quality and fertility. Dredge material has many soil-like properties, which makes it a good candidate for the main component of manufactured soil blends. Questions have arisen over contaminants of concern (heavy metals and polyaromatic hydrocarbons [PAH]) in dredge fines precluding them from reuse. One approach is to remove the fine fraction of dredge to lower the contaminant concentration; however, it may result in a lower quality soil substitute for land reclamation. In this study, soil blends were designed to compare the use of whole dredge to dredge fines (e.g., dredge with silt and clay fraction) and to assess the benefits of compost material, clay, and fertilizer additions. Dredge fines blends led to increases in soil quality, dry matter growth, plant available water, total and active C, potentially mineralizable N, and micronutrients. The addition of compost material led to better soil quality for a vast majority of the tested parameters. Dredge fines were below regulatory standards for contaminants of concern (e.g., carinogenic polyaromatic hydrocarbon and heavy metals), allowing their reuse in soil blends. Removal of fines from dredge decreases the quality of soil blends and should not be removed from dredge material for use as topsoil or in topsoil blends. The 80% (v/v) dredge fines blend with 20% (v/v) additions of compost material resulted in the greatest improvements in the assessed soil health parameters.