Implication of sludge stabilization process and polymeric material addition on nitrogen and carbon mineralization

Soil fertility deterioration has been a challenge limiting crop productivity. Recycling municipal sludge in agroecosystems proved to be an effective soil nutrient source. However, due to varied nutrient content emanating from wastewater sources and treatment processes, sludges require application rate optimization for sustainable reuse. A laboratory incubation study was conducted over 90 days to quantify carbon (C) and nitrogen (N) mineralization rate from sludge amended soils. Aerobic (AeD) sludge, anaerobic digested sludges without polymer (AnDP0) and with polymer (AnDP1) treatments were applied at 10 tons ha-1. N fractions and other parameters varied significantly with sludge treatment. AeD had significantly higher total N than AnD sludges. AeD sludge mineralized significantly higher cumulative CO2 – C than AnD. AnD sludges had higher final N mineralization rates of 43% (AnDP0) and 54% (AnDP1) against 41% from AeD sludge. Polymeric material addition increased net N mineralization rate by 10%. Cumulative mineralized N showed to be driven by the size of applied organic N pool. Applied organic N was higher in AeD relative to AnD sludges, leading to higher net N mineralized. N mineralization was faster within first 30 days of sludge application, suggesting that, for efficientmineral N utilization fromsludge, plantingmust be planned to synchronize crop N needs with this high biosolids N release period. The study showed the importance of basing sludge application rates on N content and mineralization rate rather than a single and generalized recommendation rate; a strategy that limits excess nutrient application and reducing pollution whilst enriching agroecosystems.Water Research Commission.http://www.elsevier.com/locate/crsustam2022Plant Production and Soil Scienc

Sludge stabilization process, drying depth and polymeric material addition : implication on nitrogen content, selected chemical properties and land requirement in sand drying beds

Drying beds are a simple and economical means to dewater municipal sludge and are widely used in places with a suitable climate for air-drying. However, research-based information on drying thickness/drying depth effects on nutrient content and land size requirements for sludge drying is scarce. In this study, aerobically digested (AeD), and anaerobically digested without polymer (AnDP0) and with polymer (AnDP1) sludge types were dried in sand drying beds at 5, 10, 15, 20 and 25 cm depths in South Africa. Measured nitrogen (N) fractions and other parameters were more strongly influenced by sludge types than by drying depth. Total N content followed the order of AeD > AnDP1 > AnDP0. Polymeric material addition tended to increase total and inorganic N content and reduce the length of sludge drying period and land size requirement. The study showed that larger land size is required to dry sludge at shallower depths, even though the sludge dried more quickly. Drying sludge at 15 cm was the best option across sludge types in winter, taking an average land area between 261 and 383 m2 over the fewest days of sludge drying, whereas in spring, drying at 20 to 25 cm depth was most favorable. The findings suggest that drying bed management can be based on land area requirements with little concern for biosolid quality changes. For wastewater treatment plants relying on drying in beds, adding polymeric materials may be beneficial where land area for drying beds is limited, but not otherwise. Therefore, land availability is critical in decision making for sustainable sludge drying thickness.Water Research Commission (WRC) of South Africa and EnviSafeBioC, a project financed by the Polish National Agency for Academic Exchange.http://www.mdpi.com/journal/energiespm2021Plant Production and Soil Scienc

Estimating Nitrogen Availability of Heat-Dried Biosolids

As heat-dried biosolids become more widely produced and marketed, it is important to improve estimates of N availability from these materials. Objectives were to compare plant-available N among three different heat-dried biosolids and determine if current guidelines were adequate for estimating application rates. Heat-dried biosolids were surface applied to tall fescue (Festuca arundinacea Schreb.) in Washington State, USA, and forage yield and N uptake measured for two growing seasons following application. Three rates of urea and a zero-N control were used to calculate N fertilizer efficiency regressions. Application year plant-available N (estimated as urea N equivalent) for two biosolids exceeded 60% of total N applied, while urea N equivalent for the third biosolids was 45%. Residual (second-year) urea N equivalent ranged from 5 to 10%. Guidelines for the Pacific Northwest USA recommend mineralization estimates of 35 to 40% for heat-dried biosolids, but this research shows that some heat-dried materials fall well above that range

Field microplot estimates of soil N mineralization for manured and non-manured soils

Credits for available N from past manure applications are often used in nutrient management planning. However, it is difficult to verify the accuracy of these credits. The major objective of this study was to estimate long-term effects of manure application on soil N mineralization. Specific objectives were to: 1) estimate the quantity and timing of N mineralized in manured vs. non-manured soils via an field microplot incubation method, 2) to compare N mineralized in the microplots to N mineralized in an adjacent field soil, and 3) to apply our research findings to a predictive N mineralization model. We collected soils (0-8 in depth) from sites with and without a history of manure application. Soils were incubated at a single field site in 2 inch i.d. x 8 in. long open-ended PVC microplots. A nylon bag containing ion exchange resins was placed in the bottom of each microplot to capture leached NO3- and NH4+. Microplots were installed in April, and harvested 1-2 times per month through October. Cumulative N mineralization data for each soil was fit to a sigmoid function. We then used a linear fit between cumulative net N mineralized and degree days to determine a “mineralization rate constant” for each soil. In both years, the maximum mineralization rates of 0.4 to 1.9 lb/acre per day occurred in July, corresponding to maximum soil temperatures. Over the two year study, cumulative net N mineralization per season averaged 85 ppm for three manured soils and 63 ppm per season for three non-manured soils. For the 8-inch depth measured, this amounted to an average of 152 lb N/acre for manured soils vs. 114 lb/acre for non-manured soils. Seasonal net N mineralized for the Puyallup soil in the incubation microplots (35 to 53 ppm) was similar to that measured for adjacent Puyallup soil in the field. This suggests that the microplot incubation procedure gave values that are realistic for field conditions. The mineralization rate constants developed by this study show promise in making our data transferable to other soil temperature conditions, or to portions of a growing season. However, much work remains to be done before this technique is implemented for routine use for nitrogen management

Soil and plant test calibration to improve nutrient management

Addendum to final report, Abbotsford-Sumas Aquifer Nitrate Management Project G9500254.This project evaluated soil and plant tissue tests for nitrogen monitoring in silage corn fields in Whatcom County, WA. Soil tests evaluated included the Pre-Sidedress Nitrate Test (PSNT), and the Post-Harvest Nitrate Test

Agronomic biosolids application rates for dryland wheat across a range of northwest climate zones

Predicting agronomic rates is important to derive optimum economic and environmental benefits from biosolids fertilizer applications. We conducted this research to 1) evaluate dryland wheat response to biosolids applications over a range of climate zones in the Pacific Northwest and 2) compare agronomic application rates predicted from yield curves with those predicted from published extension guidance. We applied a range of biosolids rates during the fallow year in ten on-farm dryland wheat experiments located in five counties in central and eastern Washington and in one county in north-central Oregon. Grain yield, protein, and post-harvest soil nitrate were determined. Recommended nitrogen rates for each site were calculated from Extension nutrient management guidance, and compared with biosolids agronomic rate estimates based on 95% maximum yield from the regressions generated for each site. Eight of the ten sites had quadratic yield responses. The two non-responsive sites had high pre-application levels of soil nitrate-N. Protein response was linear at most sites, while soil nitrate accumulation was variable, with the greatest increases at the least responsive sites. Field agronomic rates were within 20 lb N/acre (0 to 0.6 dry tons biosolids/acre) of recommended rates at six of the 10 sites. Greater differences at the other sites resulted from leaching, drought, or high pre-application soil N. At the eight sites that responded to N application, a median biosolids application rate of 2.2 dry ton/acre (approx 200 lb biosolids total N per acre) was required for 95% of maximum grain yield. This research demonstrated that the use of a WA fertilizer guide together with a PNW worksheet for estimating available N from biosolids gave reasonable estimates for biosolids application rates. We suspect that one of the benefits of biosolids for dryland wheat production is that wet crop years increase both grain yield potential and N mineralized from biosolids

Comparison of Raw Dairy Manure Slurry and Anaerobically Digested Slurry as N Sources for Grass Forage Production

We conducted a 3-year field study to determine how raw dairy slurry and anaerobically digested slurry (dairy slurry and food waste) applied via broadcast and subsurface deposition to reed canarygrass (Phalaris arundinacea) affected forage biomass, N uptake, apparent nitrogen recovery (ANR), and soil nitrate concentrations relative to urea. Annual N applications ranged from 600 kg N ha−1 in 2009 to 300 g N ha−1 in 2011. Forage yield and N uptake were similar across slurry treatments. Soil nitrate concentrations were greatest at the beginning of the fall leaching season, and did not differ among slurry treatments or application methods. Urea-fertilized plots had the highest soil nitrate concentrations but did not consistently have greatest forage biomass. ANR for the slurry treatments ranged from 35 to 70% when calculations were based on ammonium-N concentration, compared with 31 to 65% for urea. Slurry ANR calculated on a total N basis was lower (15 to 40%) due to lower availability of the organic N in the slurries. No consistent differences in soil microbial biomass or other biological indicators were observed. Anaerobically digested slurry supported equal forage production and similar N use efficiency when compared to raw dairy slurry

SARS-CoV-2 Omicron is an immune escape variant with an altered cell entry pathway

Vaccines based on the spike protein of SARS-CoV-2 are a cornerstone of the public health response to COVID-19. The emergence of hypermutated, increasingly transmissible variants of concern (VOCs) threaten this strategy. Omicron (B.1.1.529), the fifth VOC to be described, harbours multiple amino acid mutations in spike, half of which lie within the receptor-binding domain. Here we demonstrate substantial evasion of neutralization by Omicron BA.1 and BA.2 variants in vitro using sera from individuals vaccinated with ChAdOx1, BNT162b2 and mRNA-1273. These data were mirrored by a substantial reduction in real-world vaccine effectiveness that was partially restored by booster vaccination. The Omicron variants BA.1 and BA.2 did not induce cell syncytia in vitro and favoured a TMPRSS2-independent endosomal entry pathway, these phenotypes mapping to distinct regions of the spike protein. Impaired cell fusion was determined by the receptor-binding domain, while endosomal entry mapped to the S2 domain. Such marked changes in antigenicity and replicative biology may underlie the rapid global spread and altered pathogenicity of the Omicron variant

Investigation of hospital discharge cases and SARS-CoV-2 introduction into Lothian care homes

Background The first epidemic wave of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) in Scotland resulted in high case numbers and mortality in care homes. In Lothian, over one-third of care homes reported an outbreak, while there was limited testing of hospital patients discharged to care homes. Aim To investigate patients discharged from hospitals as a source of SARS-CoV-2 introduction into care homes during the first epidemic wave. Methods A clinical review was performed for all patients discharges from hospitals to care homes from 1st March 2020 to 31st May 2020. Episodes were ruled out based on coronavirus disease 2019 (COVID-19) test history, clinical assessment at discharge, whole-genome sequencing (WGS) data and an infectious period of 14 days. Clinical samples were processed for WGS, and consensus genomes generated were used for analysis using Cluster Investigation and Virus Epidemiological Tool software. Patient timelines were obtained using electronic hospital records. Findings In total, 787 patients discharged from hospitals to care homes were identified. Of these, 776 (99%) were ruled out for subsequent introduction of SARS-CoV-2 into care homes. However, for 10 episodes, the results were inconclusive as there was low genomic diversity in consensus genomes or no sequencing data were available. Only one discharge episode had a genomic, time and location link to positive cases during hospital admission, leading to 10 positive cases in their care home. Conclusion The majority of patients discharged from hospitals were ruled out for introduction of SARS-CoV-2 into care homes, highlighting the importance of screening all new admissions when faced with a novel emerging virus and no available vaccine

Genomic epidemiology of SARS-CoV-2 in a UK university identifies dynamics of transmission

AbstractUnderstanding SARS-CoV-2 transmission in higher education settings is important to limit spread between students, and into at-risk populations. In this study, we sequenced 482 SARS-CoV-2 isolates from the University of Cambridge from 5 October to 6 December 2020. We perform a detailed phylogenetic comparison with 972 isolates from the surrounding community, complemented with epidemiological and contact tracing data, to determine transmission dynamics. We observe limited viral introductions into the university; the majority of student cases were linked to a single genetic cluster, likely following social gatherings at a venue outside the university. We identify considerable onward transmission associated with student accommodation and courses; this was effectively contained using local infection control measures and following a national lockdown. Transmission clusters were largely segregated within the university or the community. Our study highlights key determinants of SARS-CoV-2 transmission and effective interventions in a higher education setting that will inform public health policy during pandemics.</jats:p