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The Effectiveness of Amendments in Promoting Hydric Soil Conditions in Mitigation Wetlands – Phase II

Wetland mitigation is required by Maryland Department of the Environment (MDE) to offset wetland losses due to development. Wetland creation or restoration can also be initiated to promote beneficial hydrological, biogeochemical, and biological functions or ecosystem services. In order to determine if wetland has been successfully established, hydrologic, vegetation and hydric soil indicators must be met. The three methods to demonstrate hydric soils (α,α’-dipyridyl, IRIS tubes, and redox potential) are all measures of microbially mediated iron-reducing conditions. Iron may be a key process in wetland carbon sequestration (Shimizu et al. 2013) and controlling unwanted nitrous oxide and methane emissions (Huang, Yu, and Gambrell 2009). In fiscal year 2019, the research team plans to carry out the field experiment that was originally scheduled for 2018. The general approach in field and laboratory experimentation will be to test the effectiveness of four organic matter amendments: #1 wood mulch that meets the MDOT SHA criteria for Type C compost, # 2 cow manure that meets the MDOT SHA criteria for Type A compost, #3 BLOOM a class A biosolid sourced from DC water, and # 4 switchgrass hay. The research team has obtained samples of #1 and #2 from a local contractor. The switchgrass was harvested in October 2018 from the Central Maryland Research and Education Center in Clarksville, Maryland. After addition of the amendments in field plots, the research team will be monitoring hydric soil indictors (iron-reducing conditions) using the three standard methods listed previously. Additionally, groundwater levels will be monitored in all plots. The research team will also measure microbial growth and respiration to determine the fate of carbon and nitrogen.