Bioretention cells (BRCs) are effective tools for treating urban stormwater, but nitrogen removal by these systems is highly variable. Improvements in nitrogen removal are hampered by a lack of data ...directly quantifying the abundance or activity of denitrifying microorganisms in BRCs and how they are controlled by original BRC design characteristics. We analyzed denitrifiers in twenty-three BRCs of different designs across three mid-Atlantic states (MD, VA, and NC) by quantifying two bacterial denitrification genes (nirK and nosZ) and potential enzymatic denitrification rates within the soil medium. Overall, we found that BRC design factors, rather than local environmental variables, had the greatest effects on variation in denitrifier abundance and activity. Specifically, denitrifying populations and denitrification potential increased with organic carbon and inorganic nitrogen concentrations in the soil media and decreased in BRCs planted with grass compared to other types of vegetation. Furthermore, the top layers of BRCs consistently contained greater concentrations and activity of denitrifying bacteria than bottom layers, despite longer periods of saturation and the presence of permanently saturated zones designed to promote denitrification at lower depths. These findings suggest that there is still considerable potential for design improvements when constructing BRCs that could increase denitrification and mitigate nitrogen export to receiving waters.
Biofuel production from crop residues is widely recognized as an essential component of developing a bioeconomy, but the removal of crop residues still raises many questions about the sustainability ...of the cropping system. Therefore, this study reviews the sustainability effects of crop residues removal for biofuel production in terms of crop production, soil health and greenhouse gas emissions. Most studies found little evidence that residue management had long‐term impacts on grain yield unless the available water is limited. In years when water was not limiting, corn and wheat removal rates ≥90% produced similar or greater grain yield than no removal in most studies. Conversely, when water was limiting, corn grain yield decreased up to 21% with stover removal ≥90% in some studies. Changes in soil organic fractions and nutrients depended largely on the amount of residue returned, soil depth and texture, slope and tillage. Reductions in organic fractions occurred primarily with complete stover removal, in the top 15–30 cm in fine‐textured soils. Soil erosion, water runoff and leaching of nutrients such as total nitrogen (N) and extractable soil potassium decreased when no more than 30% of crop residues were removed. Stover management effects on soil bulk density varied considerably depending on soil layer, and residue and tillage management, with removal rates of less than 50% helping to maintain the soil aggregate stability. Reductions in CO2 and N2O fluxes typically occurred following complete residue removal. The use of wheat straw typically increased CH4 emissions, and above or equal to 8 Mg/ha wheat straw led to the largest CO2 and N2O emissions, regardless of N rates. Before using crop residues for biofuel production, it should therefore always be checked whether neutral to positive sustainability effects can be maintained under the site‐specific conditions.
Biofuel production from crop residues is widely recognized as an essential component of developing a bioeconomy, but the removal of crop residues still raises many questions about the overall sustainability of the cropping system. Before using crop residues for biofuel production, it should therefore always be checked whether neutral to positive sustainability effects can be maintained under the site‐specific conditions.
Application of organic amendments (e.g., biosolidsBS, composts) to soil may provide an effective method for accumulating considerable amounts of C, but the long term stability of such C is not well ...known. We investigated study sites in Virginia to determine the amounts of C remaining in soils 7 to 27 yr following amending with biosolids and composts. The first study employed a Fauquier silty clay loam (fine, mixed, active, mesic Ultic Hapludalf) to which four treatments (control, poultry litter‐yard waste compost, biosolids compost, and poultry litter) were continuously applied during 2000–2004. The second study was conducted on a Davidson clay loam (fine, kaolinitic, thermic, Rhodic Kandiudult) to which six rates of aerobically digested biosolids (0, 42, 84, 126, 168, and 210 Mg ha–1) were applied in 1984. The third study was on a Pamunkey sandy loam (fine‐loamy, mixed, semiactive, thermic Ultic Hapludalfs) to which five rates of anaerobically digested biosolids (0, 14, 42, 70, and 98 Mg ha–1), with and without sawdust, were applied in 1996. Total soil organic C concentration and bulk density were measured to calculate C accumulation. The organic amendment‐treated soils increased C in the surface soil depth (<15 cm), ranging from 2 to 12% of C across all three sites. Soil C movement was limited to a depth of 15 cm. Evidence of C saturation was revealed in the third study site. These results demonstrate that organic amendments applied over a long time remain in soil and may contribute to C sequestration in the Mid‐Atlantic region.
Biosolids are used to improve soil physical and chemical properties. Analysis of biosolids-amended soils from multiple regions of United States using consistent analytical methods is lacking. This ...Study determined long-term biosolids application on soil pH, electrical conductivity (EC), carbon, cadmium, copper, lead, and zinc concentrations in soils from two regions in United States. At one region, little difference was observed in pH and EC between biosolids-amended surface soils and control, the second region ranged from 5.46 to 7.87 and 50.2 to 402 µS cm
−1
respectively. Trace metal levels at this region ranged from 0.76 to 3.79, 8.7 to 54.1, 15.2 to 53.9, and 26 to 207 mg kg
−1
for Cadmium, Copper, lead and Zinc respectively; with its carbon levels ranging from 14.5 to 90.0 g kg
−1
. Metal levels were within the standards for residential occupation with the 40 Code of Federal Regulations (CFR) Part 503 and should not affect soil and groundwater quality.
Exceptional Quality (EQ) biosolids may be developed into products that can rehabilitate disturbed urban soils for the production of garden vegetables. The objectives of this study were to compare ...newly developed EQ biosolids products specially tailored for urban soil use with those of established products for the purpose of identifying their capability to support germination and plant growth, as well as to quantify their plant available nitrogen (N) and phosphorus (P). Seven EQ biosolids products and an inorganic fertilizer control were compared in greenhouse bioassays employing soybean (Glycine max L.) and tall fescue (Festuca arundinacea Schreb.) to assess product quality and nutrient availability. The EQ biosolids were derived from treatment processes such as thermal drying, composting, and blending with complementary organic and mineral materials. The EQ biosolids products applied at an estimated equivalent agronomic N rate enabled adequate germination and plant growth. The N uptake by tall fescue grown with the biosolids amendments compared with known rates of inorganic N confirmed organic N availability to be approximately 40%, 20%, and 15% for thermally dried, blended, and composted EQ biosolids products, respectively. The application of these products at agronomic N rates to a soil testing adequate in P increased soil P saturation to 20%-35%, a normal range for soil not excessively enriched with P. The availability of N and P in the EQ biosolids products will permit their agronomically beneficial and environmentally sound use in urban soils.
Human wastewater biosolids, hereafter referred to as biosolids, are produced in significant quantities around the world and often applied to an extensive land mass including agricultural fields, ...forests, mine lands, and urban areas. Land-application of biosolids has been reported in peer-reviewed and non-peer-reviewed work to change soil organic carbon stocks in varying amounts. Determining the potential of soil organic carbon (SOC) stock change and sequestration from biosolids land application is critical for biosolids producers and users to gain access to carbon credit markets. Our review question is, "what is the impact of biosolids application on long-term soil carbon sequestration rates?" We look to explore this main question with the follow-up, "does biosolids processing methods and characteristics, application method, soil properties, land management and other modifiers affect rates of carbon accumulation from land-applied biosolids?" Searches will be conducted using online databases (i.e., Web of Science Core Collection, CAB Abstracts, Scopus, ProQuest Dissertations & Theses Global), search engines (Google Scholar and Microsoft Academic), and specialist websites to find primary field studies and grey literature of biosolids land-application effects on soil organic carbon stocks. We will use English search terms and predefined inclusion criteria of: (1) a field study of at least 24 months that reports soil organic carbon/matter (SOC/SOM) concentrations/stocks; (2) has two types of treatments: (i) a control (non-intervention AND/OR synthetic fertilizer) AND (ii) a biosolids-based amendment; and (3) information of amendment properties and application dates and rates to estimate the relative contribution of the applied materials to SOC changes. We will screen results in two stages: (1) title and abstract and (2) full text. A 10% subset will be screened by two reviewers for inclusion at the title and abstract level and use a kappa analysis to ensure agreement of at least 0.61. All results in the full text stage will be dual screened. Data will be extracted by one person and reviewed by a second person. Critical appraisal will be used to assess studies' potential bias and done by two reviewers. A meta-analysis using random effects models will be conducted if sufficient data of high enough quality are extracted.
Greenhouse gas (GHG) emissions from crop residue management have been studied extensively, yet the effects of harvesting more than one crop residue in a rotation have not been reported. Here, we ...measured the short-term changes in methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2) emissions in response to residue removal from continuous corn (Zea mays L.) (CC) and corn–wheat (Triticum aestivum L.)–soybean (Glycine max L. Merr.) (CWS) rotations in the Mid-Atlantic USA. A first experiment retained five corn stover rates (0, 3.33, 6.66, 10, and 20 Mg ha−1) in a continuous corn (CC) in Blacksburg, VA, in 2016 and 2017. Two other experiments, initiated during the wheat and corn phases of the CWS rotation in New Kent, VA, utilized a factorial combination of retained corn (0, 3.33, 6.66, and 10.0 Mg ha−1) and wheat residue (0, 1, 2, and 3 Mg ha−1). Soybean residue was not varied. Different crop retention rates did not affect CO2 fluxes in any of the field studies. In Blacksburg, retaining 5 Mg ha−1 stover or more increased CH4 and N2O emissions by ~25%. Maximum CH4 and N2O fluxes (4.16 and 5.94 mg m−2 day−1) occurred with 200% (20 Mg ha−1) retention. Two cycles of stover management in Blacksburg, and one cycle of corn or wheat residue management in New Kent did not affect GHG fluxes. This study is the first to investigate the effects of crop residue on GHG emissions in a multi-crop system in humid temperate zones. Longer-term studies are warranted to understand crop residue management effects on GHG emissions in these systems.
Exceptional quality (EQ) biosolids may be used to rehabilitate disturbed urban soils for vegetable production in urban gardens. The objectives of this study were to investigate the effects of various ...EQ biosolids products on urban soil properties and vegetable yield. Field research was conducted at Blacksburg, VA, in an urban subsoil fill from a nearby construction site. Three EQ biosolids products were applied biannually at agronomic nitrogen (N) rates (fall 2016–2017, and summer 2017–2018) and annually at land reclamation rates (5× agronomic N rate; fall 2016–2017). A heat‐dried and pelletized EQ biosolids product and inorganic fertilizer were applied biannually at agronomic N rate only. Biosolids increased soil C storage vs. the control by 37 to 84% after 2 yr. Soil N availability was less than expected based on previous greenhouse research even after cumulative biosolids rates. Lower N availability likely was due to low organic matter and high clay concentrations that reduced organic N mineralization. Cabbage Brassica oleracea L. var. capitata L. (∼3.1 kg m –2 ) and Siberian kale Brassica napus L. subsp. napus var. pabularia (DC.) Alef. (∼1.1 kg m –2 ) yields were greater with reclamation rates than with the inorganic fertilizer (1.0 kg m –2 and 0.4 kg m –2 , respectively) in fall 2017. Despite limiting soil physicochemical conditions, biosolids addition at reclamation rates showed greater potential to increase vegetable yield after 2 yr of application.
Current trends in agriculture have moved toward more sustainable cultivation systems with higher efficiency of input use. A variety of materials, derived from different resources, can serve as a crop ...nutrient sources. An Integrated Plant Nutrition System (IPNS) uses the combined and harmonious use of inorganic, organic and biological nutrient resources to maximize efficiency of inputs. We evaluated the effects of commercial nitrogen (N) fertilizer, humic acid compounds (HA), compost/manure teas and bioinoculants as inorganic, organic and biological resources, respectively and their synergy over three years on corn (Zea mays L.) in the Mid-Atlantic USA. The individual and combined application of HA and biofertilizer following the IPNS influenced corn height and leaf greenness to varying degrees, most likely due to biostimulant effects. In 2017, corn height, NDVI, greenness and vigor responded positively to biostimulant application to varying magnitudes and growth stages, however grain yield and nutrient content were not affected. In combined studies from 2018 and 2019 corn height was not impacted by biostimulant application but NDVI, photosynthetic efficiency, greenness and vigor were increased at different doses and corn growth stages. The combined use of HA + biofertilizer (Microlife Humic + Microgeo) was the only treatment leading to increased grain yield. This study demonstrates that the individual and combined application of HA and biofertilizer can influence corn growth and vigor at various points during the growing season. However, the current study cannot conclusively confirm that the integrated use of HA and biofertilizers (IPNS) is a better practice than the application of each compound individually.
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