Field-based investigations on phytostabilization of a contaminated military site using biofuel crop and soil amendments

Z. Almasarya, Ganga M. Hettiarachchia, K. L. Roozebooma, L. C. Davisb, L. E. Ericksonc, T. Toddd, V. Pidlisnyuke, T. Stefanovskaf and J. Trogle

aDepartment of Agronomy, Kansas State University, Manhattan, KS 66506, USA

bDepartment of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS 66506, USA

cDepartment of Chemical Engineering, Kansas State University, Manhattan KS 66506, USA

dDepartment of Plant Pathology, Kansas State University, Manhattan KS 66506, USA

eJan Evangelista Purkyne University, Faculty of the Environment, Usti nad Labem, Czech Republic

fNational University of Life and the Environment, Faculty of Plant Protection and Biotechnology, Kyiv, Ukraine

ganga@ksu.edu

Extensive areas of productive land can be contaminated by potentially toxic substances due to military activities. The most common and widespread metal contaminant in military lands is lead (Pb). Field experiments were begun at Fort Riley, Kansas U.S.A. in 2015 with a pilot experiment evaluating different propagules in an area with soil total Pb concentration of about 1000 mg/kg and neutral pH. In 2016, another field study was initiated to evaluate soil amendments and planting procedures using a randomized complete block design with four replications. The main objectives of these studies were to determine feasibility of using miscanthus (a second generation biofuel crop) for phytostabilization of this contaminated military site and to evaluate the effect of soil amendments on miscanthus growth, soil-plant Pb transfer, bioaccessibility of soil Pb, and soil health. Based on soil characteristics, five treatments were selected: (i) control plots without tillage and left with natural vegetation, (ii) no tillage, no additional amendments and planted with miscanthus, (iii) tilled soil, no additional amendments and planted with miscanthus, (iv) tilled soil amended with inorganic P (triple superphosphate applied at 5:3 Pb:P molar ratio) and planted with miscanthus, and (v) tilled soil amended with organic P source (class B biosolids applied at 45 Mg/ha, the organic amendment rate used by Kansas Department of Health and Environment for other remediation plots in Kansas) and planted with miscanthus. Soil samples were collected before planting and after each harvest. The above-ground biomass was harvested in early December each year, and dry matter yield was determined. Subsamples of plant material were analyzed for nutrients and Pb. Results from the first year (2016) showed that tilling and soil amendments increased the dry matter yield, and that effects of soil amendments on plant Pb concentration and bioaccessibility of soil Pb were promising. Although there were no differences in the biomass harvested in the second year of growth (2017), both total Pb uptake and Pb concentrations in plant tissues were significantly lower in the miscanthus grown in plots amended with biosolids compared to the miscanthus grown in plots with no added P. Soil extracellular enzyme activities and relative abundances of various nematode family groupings were also measured as soil health parameters, and the results will be discussed. Analysis of samples from the third year of growing season (2018) is underway.

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