Environmental Science & Technology
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Item High Quality Biosolids: Assessment of Nitrogen Mineralization and Potential for Improving Highway Soils(2019) Zhu, Chenglin; Felton, Gary K; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)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.Item BLOOM BIOSOLIDS: WHAT IS THEIR MICROBIAL COMMUNITY AND HOW DO THEY AFFECT SOIL AND PLANT HEALTH?(2019) Baballari, Eni; Yarwood, Stephanie; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Biosolids are rich in nutrients and organic matter, and are known to improve and maintain productive soils and stimulate plant growth. D.C. Water’s new Class A biosolids product, Bloom, was evaluated for its impact on plant and soil health. Using molecular tools, Bloom was examined for the presence of functional genes that would indicate the presence of microbes capable of improving plant growth (i.e.nitrifiers, N- fixers). Using greenhouse and laboratory experiments, we determined Bloom’s effect on plant growth, carbon and nitrogen cycling. Bloom has both nitrifying and N-fixing microbes, but their gene numbers vary depending on the stage of production. We show that plants, such as cucumber and tomato, grown in soil amended with Bloom produce more leaves and stems and have higher aboveground biomass, and soybeans produced more bean pods. Lastly, we found that N-mineralization is higher in soil amended with Bloom, even after one growing season, providing increased nutrients.Item SOIL ORGANIC CARBON IN MID-ATLANTIC REGION FOREST SOILS: STOCKS AND VERTICAL DISTRIBUTION(2019) Colopietro, Daniel John; Weil, Ray R; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Soil contains the largest terrestrial pool of organic carbon (Boschi et al., 2018) and temperate forest soils have been a major sink for atmospheric carbon; however, determining the size of the soil organic carbon stock can be problematic. Sampling practices vary for sampling depth, and determining the density of the soil. The aforementioned standard practices need to be revised if the size of SOC stocks are to be accurately quantified, to establish a global SOC baseline. A soil monitoring of 414 forested sites within 11 national parks in the National Capital Region (Schmit, 2014) was conducted over 10 years. Samples were collected from the leaf litter and each soil horizon to 1 meter depth. Soil bulk density (Db) was determined by the core method for the A horizons, and proxy Db values were investigated for the subsoil. The vertical distribution of SOC concentration and stocks were evaluated with respect to soil order, physiographic region/landform, drainage class and parent material.Item DEEP SOIL NITROGEN CAPTURE AND RECYCLING BY EARLY-PLANTED, DEEP-ROOTED COVER CROPS(2018) Hirsh, Sarah Marie; Weil, Ray R; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The overall purpose of this study was to improve the efficiency of nitrogen (N) cycling in Mid-Atlantic cropping systems through the use of cover crops. Our focus was on describing soil inorganic N pools (0-210 cm deep) and investigating the potential for cover crops to scavenge and recycle deep soil N. Few agronomic studies consider soil properties and processes deeper than the upper 20 to 30 cm, as the majority of roots, amendments, and practices such as fertilizer application or tillage occur on the soil surface or in the topsoil. We 1) assessed amounts of deep soil N on 29 farms in the Mid-Atlantic region, 2) used 15N tracer to investigate the capacity of various cover crops with early- or late-planting dates to capture and recycle deep soil N, and 3) investigated early-planted cover crop systems on 19 farm trials to assess their performance on farms with various soils with diverse management practices. We found that on average 253 kg N ha-1 of inorganic N remained in the soil following summer crops, 55% from 90-210 cm deep. Soil following soybean had the same amount or more of inorganic N than soil following corn throughout the soil profile. Using 15N isotopic tracer, we determined that radish, rye, and radish/rye mixes with and without crimson clover all could capture N from deep soil (60+ cm), but in order for cover crops to capture agronomically meaningful amounts of nitrate-nitrogen (NO3-N) from deep soil, they had to be planted by early-September. Cover crop trials on 19 farms indicated that, while variable site-by-site, early-planted cover crops tended to accumulate substantial N in the fall and reduce residual soil NO3-N levels substantially in the fall and spring. Cover crops also impacted subsequent corn growth and yield, with winter cereal tending to cause lower yields or increased corn N fertilizer needs compared to a no cover crop control, and forage radish sometimes leading to higher yields compared to the control. Overall, cover crops are effective at scavenging deep soil N in the fall, before winter leaching occurs, and under certain conditions, can release N for subsequent crops.Item Novel Applications in Wetland Soils Mapping on the Delmarva Coastal Plain(2018) Goldman, Margaret Anne; Needelman, Brian A; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)On the Delmarva Peninsula, depressional wetlands provide a range of ecosystem services, including water purification, groundwater recharge, provision of critical habitat, and carbon storage. Concern for the health of the Chesapeake Bay and the establishment of the Bay Total Maximum Daily Load have led to growing interest in restoring depressional and other wetland types to mitigate agricultural nitrogen inputs. The ability of natural resource managers to implement wetland restoration to address nonpoint source pollution is constrained by limited spatial information on hydrogeologic and soil conditions favoring nitrogen removal. The goal of this study was to explore the potential of new digital soil mapping techniques to improve identification of wetland soils and map soil properties to improve assessment of wetland ecosystem services, including removing excess nitrogen, and inform natural resource decision making. Previous research on digital soil mapping has focused largely on the development of medium to low-resolution general purpose soil maps in areas of heterogeneous topography and geomorphology. This study was unique in its focus on mapping wetland soils to support wetland restoration decisions in a low relief landscape. A digital soil mapping approach involving the spatial disaggregation of soil data map units was used to create maps of natural soil drainage and texture class. The study was conducted in the upper part of the Choptank River Watershed on central Delmarva, where depressional wetlands occur in high densities and historical loss of wetlands is estimated to be high compared to similar Maryland watersheds. The soil disaggregation techniques developed in this study were successful in creating a more refined representation of natural soil drainage and texture class in forested depressional wetlands. Comparison of the disaggregated soils map with recently developed time-series inundation maps of the region demonstrate the need for further research to understand how indicators of historic and current hydrologic conditions can guide operational soils and wetland mapping and inform wetland restoration decisions.Item Impact of Restoration Activity on Wetland Soil Properties and Functions(2018) Palardy, Christopher Andrew; Rabenhorst, Martin C; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Due to the essential nature of wetlands and their historic losses, wetland restoration has been a recent focus of conservation activity. The objective of this study was to compare selected physical soil properties and those properties and processes associated with carbon sequestration in restored and natural freshwater depressional wetlands on the Delmarva Peninsula. Three distinct hydrological zones within nine restored and five natural wetlands were sampled and monitored over the course of a year. As a result of earthmoving activities, restored wetlands demonstrated significant compaction, potentially limiting root and hydrological infiltration. Restored wetlands also demonstrated shorter periods of saturation, which led to increased carbon decomposition rates. As a result of soil disturbance, restored wetlands had significantly lower carbon stocks than natural wetlands. Restored wetlands also demonstrated no difference in carbon content across the three hydrological zones, the time since restoration being too short for carbon stocks to appreciably accumulate.Item Identifying Problematic Hydric Soils Derived from Red Parent Materials in the United States(2018) Mack, Sara Christine; Rabenhorst, Martin C; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Hydric soils derived from some red parent materials are “problematic” to identify during wetland delineations because they resist redox-induced color changes. These (PRPM) soils can be identified using the F21 – Red Parent Material field indicator, but the distribution and cause of the phenomenon, remains uncertain. The objectives of this study were to identify locations where PRPM occurs for appropriate use of the F21 field indicator throughout the country, and to better understand why PRPM soils resist redox-induced color changes. We found that PRPM is associated with sedimentary, hematite-rich, “red bed” formations and the deposits derived from them. Guidance maps have been developed showing where use of F21 is appropriate to support hydric soil (and therefore wetland) delineations impacted by PRPM. We also demonstrated that the cause of PRPM appears to be related to larger crystallite sizes of hematite in PRPM soils.Item Release, Survival, And Removal of Bovine Manure-Borne Indicator Bacteria Under Simulated Rainfall(2017) Stocker, Matthew Daniel; Hill, Robert L; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The effects of simulated rainfall intensities and its interactions with manure consistency and weathering on the release, survival, and removal of fecal indicator bacteria, Escherichia coli and enterococci, from land-applied dairy manure were evaluated. Rainfall intensity had significant effects on the number of bacteria in the soil following rainfall. Bacteria concentrations in soil decreased with increased soil depths and the topmost centimeter of soil accounted for the greatest proportion of bacteria. Escherichia coli persisted longer than enterococci once removed from manure. Manure consistency was not a significant factor in the removal of bacteria when manure was fresh, but as manure weathering progressed, consistency became a significant factor. The Vadas-Kleinman-Sharpley model was preferred over the exponential model for simulating the removal of manure-borne bacteria. Results of this work will be useful for improving predictions of the human health risks associated with manure-borne pathogenic microorganisms.Item Evaluating Soil Phosphorus Dynamics over Time(2017) Lucas, Emileigh Rosso; Coale, Frank J; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Agricultural nutrient management became mandatory in Maryland (MD) due to water quality concerns. Phosphorus (P) management is complex due to the stability of P in the soil, nutrient mass imbalance, and “legacy” P. To explore how potential P application bans impact historically manured fields, agronomic and environmental soil tests were conducted on plots treated with five manure-P rates, then no P applications, spanning 15 years. Mehlich-3 extractable P (M3P) declined slowly and then generally did not change during the last six years. Phosphorus saturation declined slowly or not significantly. Excessive P soils had sufficient P for crop growth in solution. Phosphorus saturation and M3P were compared in fifty sites across MD pre- and post- nutrient management planning. Results showed an increase in P concentration of Maryland agricultural fields. This response was logical, as better management would increase below-optimum P concentrations, and the regulations were not designed to draw down P.Item NITROUS OXIDE EMISSIONS IN COVER CROP-BASED CORN PRODUCTION SYSTEMS(2016) Davis, Brian Wesley; Needelman, Brian A; Mirsky, Steven B; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Nitrous oxide (N2O) is a potent greenhouse gas; the majority of N2O emissions are the result of agricultural management, particularly the application of N fertilizers to soils. The relationship of N2O emissions to varying sources of N (manures, mineral fertilizers, and cover crops) has not been well-evaluated. Here we discussed a novel methodology for estimating precipitation-induced pulses of N2O using flux measurements; results indicated that short-term intensive time-series sampling methods can adequately describe the magnitude of these pulses. We also evaluated the annual N2O emissions from corn-cover crop (Zea mays; cereal rye [Secale cereale], hairy vetch [Vicia villosa], or biculture) production systems when fertilized with multiple rates of subsurface banded poultry litter, as compared with tillage incorporation or mineral fertilizer. N2O emissions increased exponentially with total N rate; tillage decreased emissions following cover crops with legume components, while the effect of mineral fertilizer was mixed across cover crops.
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