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Biochar Enhances Seed Germination in a Legacy Mining Soil
Citation:
Olszyk, D, T Shiroyama, R. Coulombe, G. King, M. Polcher, J. Novak, AND M G Johnson. Biochar Enhances Seed Germination in a Legacy Mining Soil. Annual North American meeting of the Society of Environmental Toxicology and Chemistry, Sacramento, CA, November 04 - 08, 2018.
Impact/Purpose:
Past mining activities in the United States have left a legacy of heavy metal contaminated soils, which need to be cleaned up to allow for healthy plants on the site, and to prevent water and soil pollution. The EPA has regulatory authority, especially under Comprehensive Environmental Response, Compensation, and Liability Act (Superfund) to oversee cleanup of these sites; and responsibility to regions, states and local communities under the Office of Research and Development’s Safe and Healthy Community Research Program to develop new techniques to assist in this cleanup. Of special concern to EPA’s Region 7 is the historic lead and zinc mining occurred in southwestern Missouri, southeastern Kansas, and northeastern Oklahoma known as the Tri-State mining district, which has a large area of degraded soils where it is difficult to establish vegetation. This research was designed to determine if a newly developed technique, addition of biochar to soils, could assist revegetation efforts. Biochar is the carbon-rich material remaining heating of waste organic materials in a no, or low oxygen atmosphere, which has been shown to improve soil chemistry such as acidity (pH), tie up contaminants such as heavy metals, and improve soil characteristics favorable to plants such as water-holding capacity and fertility. We evaluated the potential for biochar made from local waste materials to enhance seed germination and early seedling growth for six native grass species that could be used in revegetation. Nearly all types of biochar significantly increased early seedling growth, measured as an increase in dry weight. The plant species, switchgrass and Indiangrass especially grew better with biochar. Canada and Virginia wildrye growth also was increased by some biochars, but big bluestem and little bluestem growth was largely unaffected by biochar. Increased seedling growth with biochar was associated with an increase in soil pH, and increases in soil electrical conductivity and phosphorus concentration, especially with the higher nutrient content barnyard manure and prairie hay biochars. Thus, this study specifically indicated candidate plant species and biochar types useful for revegetation of the locally important sites in the Tri-State Mining area, providing immediately useful information to alleviate a soil pollution problem in Region 7. More broadly, the study illustrated the potential for techniques developed under ORD’s biochar research program to enhance plant growth by improving soil chemistry, thus increasing the potential for success of vegetation reestablishment to degraded soils across the United States.
Description:
Biochar, the carbon-rich material remaining after pyrolysis (heating in low oxygen atmosphere) of cellulosic feedstocks, has the potential as a soil amendment to sequester contaminants, improve soil water-holding capacity, and increase nutrient retention thereby enhancing soil conditions to benefit plant growth. Thus the benefits of biochar could enhance the establishment and growth of plants for mine site revegetation. We evaluated the potential for different biochar types and application rates on grassland species being considered for revegetation of land affected by historic lead and zinc mining in southwestern Missouri. We used a seed germination test to determine the effects of biochar on seed germination and early seedling growth for six plant species, as well as key soil characteristics, pH and EC for plants growing in a lead/zinc mine soil, with the lead-containing wastes removed. This study was a preliminary screening of plants growing on amended mine soil before full-fledged greenhouse and field studies. Plant species were Andropogon gerardii (ANGE, big bluestem), Elymus Canadensis (ELCA, Canada wildrye,), Elymus virginicus (ELVI, Virginia wildrye), Panicum virgatum (PAVI, switchgrass), Schizachyrium scoparium (SCSC, little bluestem), and Sorghastrum nutans (SONU, Indiangrass). Biochar was made from barnyard manure (BM), yard debris (YD), hardwood pellets (HP), cedar wood (CW) and prairie hay (PH) pyrolyzed at 350, 500 and 700 °C, and applied at rates of 1, 2.5 and 5% by weight. While there were few effects of biochar on seedling emergence, early seedling growth measured as dry weight was significantly increased by a number of the biochars. Species responded differently, as growth of PAVI and SONO seedlings growth was increased by nearly all biochars, ELCA and ELVI growth was increased by some biochars, and ANGE and SCSC growth was largely unaffected by biochar. Soil pH was increased by all biochars, and soil extractable phosphorus (EP) was increased by some of the biochar treatments, but especially by the higher nutrient content BM and PH biochars. Soil electrical conductivity (EC) was increased by BM and PH. Nearly all effects of biochar on pH, EP and EC were greatest at the 5% biochar application rate. This study indicated the potential for biochar to enhance early seedling growth in mine affected soils, largely by improving soil chemical characteristics.