Browsing by Author "Pawlett, Mark"

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    Agricultural intensification reduces selection of putative plant growth-promoting rhizobacteria in wheat
    (Oxford University Press (OUP), 2024-01-01) Reid, Tessa E.; Kavamura, Vanessa N.; Torres-Ballesteros, Adriana; Smith, Monique E.; Abadie, Maïder; Pawlett, Mark; Clark, Ian M.; Harris, Jim A.; Mauchline, Tim H.
    The complex evolutionary history of wheat has shaped its associated root microbial community. However, consideration of impacts from agricultural intensification has been limited. This study investigated how endogenous (genome polyploidization) and exogenous (introduction of chemical fertilizers) factors have shaped beneficial rhizobacterial selection. We combined culture-independent and -dependent methods to analyze rhizobacterial community composition and its associated functions at the root–soil interface from a range of ancestral and modern wheat genotypes, grown with and without the addition of chemical fertilizer. In controlled pot experiments, fertilization and soil compartment (rhizosphere, rhizoplane) were the dominant factors shaping rhizobacterial community composition, whereas the expansion of the wheat genome from diploid to allopolyploid caused the next greatest variation. Rhizoplane-derived culturable bacterial collections tested for plant growth-promoting (PGP) traits revealed that fertilization reduced the abundance of putative plant growth-promoting rhizobacteria in allopolyploid wheats but not in wild wheat progenitors. Taxonomic classification of these isolates showed that these differences were largely driven by reduced selection of beneficial root bacteria representative of the Bacteroidota phylum in allopolyploid wheats. Furthermore, the complexity of supported beneficial bacterial populations in hexaploid wheats was greatly reduced in comparison to diploid wild wheats. We therefore propose that the selection of root-associated bacterial genera with PGP functions may be impaired by crop domestication in a fertilizer-dependent manner, a potentially crucial finding to direct future plant breeding programs to improve crop production systems in a changing environment.
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    Amenity grassland quality following anaerobic digestate application
    (Wiley, 2018-06-19) Pawlett, Mark; Owen, Andy; Tibbett, Mark
    Anaerobic digestate applied to land is a source of readily available nutrients, yet there is a paucity of knowledge regarding effects on grassland. To address this, we investigated the viability of using digestate as an alternative to mineral fertilizer for Lolium perenne L. grassland maintenance. We present findings of two independent field‐trials, where food‐waste digestate was applied over two growing seasons at two rates (100 and 200 kg N ha−1 year−1) and compared to mineral fertilizer (N:P:K‐12:4:6 at 100 kg N ha−1 year−1) and control (no additions) plots. L. perenne nutrition (N, P and K), chlorophyll and sward composition were assessed in the summer and autumn to observe treatment and seasonal effects. The sward benefited from digestate application in the summer with reduced occurrence of dead L. perenne. Both the digestate and mineral fertilizer shifted the sward composition similarly and in favor of Poa annua L. in summer and L. perenne in autumn, with reduced broad‐leaved weeds and bare soil coverage regardless of season. Quantities of foliar N and K uptake were similar between the digestate and mineral fertilizer; however, the highest rate of digestate application was required to supply similar quantities of P to the grass compared to the mineral fertilizer. Grass chlorophyll was not adversely affected by the high ammonium‐N in the digestate. These broadly positive results for digestate present opportunities for the development of digestate use as a fertilizer on amenity grassland such as outfields in sports facilities, parks, and road verges as well as showing potential for supplementing the fertility of pasture systems.
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    Bioengineering remediation of former industrial sites contaminated with chemical mixtures
    (Elsevier, 2023-05-18) Atai, Emmanuel; Jumbo, Raphael; Andrews, Richard; Cowley, Tamazon; Azuazu, Ikeabiama; Coulon, Frederic; Pawlett, Mark
    Former gasworks sites are known to be contaminated with complex chemical mixtures that require remediation before redevelopment. Bioamendments such as biochar and spent mushroom compost (SMC) offer a green and sustainable remediation approach to help tackle this issue. However, the effectiveness of different biochar types and their interactions with the soil microbial community is still not well understood. To address this, a full factorial microcosm experiment was carried out using biochar derived from rice husk (RHB) and wheat straw (WSB) mixed with soil from a former gasworks site at varying concentrations (0%, 2.5%, and 5%), with and without SMC. The experiment aimed to evaluate the fate of contaminants including alkanes, PAHs, and metals, and their effect on the soil microbial community, as well as the implications for remediation endpoints. The results showed that the bioamendments had an average TPH reduction of 92%, with SMC and WSB-SMC having the highest degradation rates at 93%. While the bioamendments did not significantly affect the extent of TPH removal compared to the control, they did improve the degradation of high molecular weight (HMW) PAHs, particularly in RHB-SMC for EC17-20 (60%) and EC21-35 (62%) of total PAH concentration, and in WSB-SMC for HMW bioavailable PAH concentration (89%). The bioamendments also affected the partitioning and distribution of metals after 120 days of treatment, leading to decreased available phase fractions. The treatments increased microbial abundance in the soil, with Gram positives, Gram negatives, and fungi increasing by 4%, 8%, and 38%, respectively, after 120 days, particularly in SMC and mixed treatments. This was mirrored in increased microbial soil respiration. After 120 days, low metal (178 ± 5 mg/kg) and TPH (21 ± 7 mg/kg) bioavailability translated into higher EC50 (10624 ± 710 mg/L), indicating lower toxicity. There was a strong correlation between bioavailability and toxicity of TPH and metals with microbial relative abundance and activity. In summary, while green and sustainable remediation may accelerate the remediation process, monitored natural attenuation may be sufficient for site reclamation. However, this strategy, as demonstrated here, can reduce metal bioavailability, and promote the biodegradation of HMW PAHs.
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    The contribution of natural burials to soil ecosystem services: review and emergent research questions
    (Elsevier, 2023-11-22) Pawlett, Mark; Girkin, Nicholas T.; Deeks, Lynda K.; Evans, Daniel L.; Sakrabani, Ruben; Masters, Peter; Garnett, Kenisha; Marquez-Grant, Nicholas
    The modern funeral industry faces many environmental risks and challenges, such as the use of sustainable materials for coffins, the release of potentially damaging materials and organisms to the soil and groundwater, and reduced space available for cemeteries. “Natural burial” proposes an alternative and more sustainable funeral practice, omitting the use of preservatives that inhibit body decomposition, thus proposing to reduce environmental degradation and benefit soil ecosystem services. This study conducted a literature review to identify proposed risks and benefits of “natural” compared to “traditional” burial practices, identifies knowledge gaps, and proposes further research questions. The approach was multidisciplinary, including literature from soil, environmental, forensic, and archaeological sciences, and the Humanities. Results identified that here are some clear environmental benefits to natural burial, such as habitat creation and aboveground biodiversity. However, there is a substantial deficit of research that compares the unseen risks and benefits of natural burial practice. Multiple potential risk factors include: (i) groundwater contaminated with biochemical products of decomposition, pathogens, and pharmaceutical products, (ii) atmospheric emissions, including greenhouse gases (CO2, CH4, N2O). There is also a deficit of information related to the release of cadaver decomposition products to soil ecological processes. More detailed scientific research is required to identify the risks and benefits of funeral options, thus develop fit for purpose regulations and legislation and to describe the cultural incentives for natural burial. This paper identifies key areas of research required to understand and mitigate the potential environmental and cultural implications of human burial practices.
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    Cover crops for sustainable maize production.
    (2017-12) Mancini, Agnese; Pawlett, Mark; Deeks, Lynda K.
    Conventional maize-after-maize in the UK is frequently associated with soil compaction, runoff and soil erosion, due to a late autumn harvest and a post-harvest management that leaves minimal soil protection. Consequently, maize cultivation leads to on-site soil degradation and off-site environmental pollution. Soil conservation practices such as cover cropping could improve the sustainability of maize. Two field experiments were established within commercially grown maize (Herefordshire) in two consecutive years to investigate the role of different species of cover crops in reducing runoff, preventing soil erosion and enhancing soil microbial community. Experiment 1 compared common non-cover crop post-harvest managements with Lolium multiflorum and Secale cereale. Experiment 2 compared Lolium multiflorum and the mixtures Lolium multiflorum & Vicia villosa and Lolium multiflorum & Trifolium alexandrinum with the traditional method of post-harvest wintered maize stubbles without cover crops. Runoff and soil loss were monitored using enclosed erosion plots periodically sampled. Soil was tested for chemical parameters such as organic matter, organic carbon, total nitrogen, available phosphorus, and biological parameters such as microbial and fungal biomass, phospholipid fatty acid analysis and multiple substrates induced respiration. Additionally, during Experiment 2 easily available glomalin related soil proteins and aggregate stability were measured. Results showed a trend in the reduction of runoff and soil erosion. However, no significant differences were recorded. Overall, the impact of cover crops on soil microbiology was limited. Cover crops had a priming effect during Experiment 1 that led to a reduction of organic matter and organic carbon due to microbial activity. In Experiment 2 the relative abundance of fungi increased in the cover crop treatments. This was possibly due to the decrease of easily available nutrients and the increase of plant root debris, which are more available to fungi rather than bacteria. Cover crops seemed a practical option to improve the sustainability of maize production due to lack of an adverse impact on maize yield and the encouraging results on runoff, soil erosion and soil fungi. However, the effects were limited and further investigation is needed to prove the impact of cover crops in the long-term.
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    Data - Immobilisation of anaerobic digestate supplied nitrogen into soil microbial biomass is dependent on lability of high organic carbon mat
    (Cranfield University, 2024-03-11 09:09) Van Midden, Christina; Harris, Jim; Shaw, Liz; Sizmur, Tom; Morgan, Hayden; Pawlett, Mark
    Research data for a 150 day incubation study to determine the effects of mixing high organic carbon materials into anaerobic digestate on soil microbial immobilisation of digestate supplied nitrogen and on soil microbial communities. This dateset contains raw data on microbial biomass carbon and nitrogen, soil available nitrogen (ammonium-N and total oxides of nitrate-nitrite), total soil nitrogen, and PLFA biomarkers.
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    Data supporting 'Bioengineering remediation of former industrial sites contaminated with chemical mixtures'
    (Cranfield University, 2023-05-19 09:56) Atai, Emmanuel; Pawlett, Mark; Coulon, Frederic
    Research data for a 120-day incubation study to determine the effects and influence of rice husk and wheat straw biochar, as well as spent mushroom compost, on the fate and behaviour of hydrocarbons and metals, as well as their influence on soil microbial communities in a genuinely contaminated former gasworks soil. Specifically, the data included are the changes in alkanes and PAH, metals (total and bioavailable distribution and partitioning), PLFA, Respiration, Microtox, and the respective statistics outputs including anova, principal component analysis and correlation (presented as draftsman charts)
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    Data Supporting 'Efficacy of bioadmendments in reducing the influence of salinity on the bioremediation of oil-contaminated soil'
    (Cranfield University, 2023-06-16 15:49) Atai, Emmanuel; Pawlett, Mark; Coulon, Frederic
    Data to support the paper: 'Efficacy of bioadmendments in reducing the influence of salinity on the bioremediation of oil-contaminated soil', which include hydrocarbon alkanes and PAHs, PLFA Mol% to give the microbial community dynamics and abundance of the groups, basal and multisubstrate respiration, and the correlation of the entire datasets. Some statistics and Charts were included in the data.
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    Dataset for paper: Microbial community composition of translocated ancient woodland soil: a case study
    (Cranfield University, 2022-01-07 11:50) Hannam, Jacqueline; Pawlett, Mark; Borchers, Nicolas
    Raw data for study Microbial community composition of translocated ancient woodland soil: a case study. Includes soil pH, organic matter, available N, available P, microbial biomass, microbial activity, PLFA biomarkers
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    Defining and quantifying the resilience of responses to disturbance: a conceptual and modelling approach from soil science
    (Nature Publishing Group, 2016-06-22) Todman, Lindsay; Fraser, Fiona; Corstanje, Ronald; Deeks, Lynda K.; Harris, Jim A.; Pawlett, Mark; Ritz, Karl; Whitmore, A. P.
    There are several conceptual definitions of resilience pertaining to environmental systems and, even if resilience is clearly defined in a particular context, it is challenging to quantify. We identify four characteristics of the response of a system function to disturbance that relate to “resilience”: (1) degree of return of the function to a reference level; (2) time taken to reach a new quasi-stable state; (3) rate (i.e. gradient) at which the function reaches the new state; (4) cumulative magnitude of the function (i.e. area under the curve) before a new state is reached. We develop metrics to quantify these characteristics based on an analogy with a mechanical spring and damper system. Using the example of the response of a soil function (respiration) to disturbance, we demonstrate that these metrics effectively discriminate key features of the dynamic response. Although any one of these characteristics could define resilience, each may lead to different insights and conclusions. The salient properties of a resilient response must thus be identified for different contexts. Because the temporal resolution of data affects the accurate determination of these metrics, we recommend that at least twelve measurements are made over the temporal range for which the response is expected.
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    Demonstration of a multi-technique approach to assess glacial microbial populations in the field
    (Cambridge University Press, 2016-04-04) Barnett, Megan J.; Pawlett, Mark; Wadham, Jemma L.; Jackson, Miriam; Cullen, David C.
    The ability to perform microbial detection and characterization in-field at extreme environments, rather than on returned samples, has the potential to improve the efficiency, relevance and quantity of data from field campaigns. To date, few examples of this approach have been reported. Therefore, we demonstrate that the approach is feasible in subglacial environments by deploying four techniques for microbial detection: real-time polymerase chain reaction; microscopic fluorescence cell counts, adenosine triphosphate bioluminescence assay and recombinant Factor C assay (to detect lipopolysaccharide). Each technique was applied to 12 subglacial ice samples, 12 meltwater samples and two snow samples from Engabreen, Northern Norway. Using this multi-technique approach, the detected biomarker levels were as expected, being highest in debris-rich subglacial ice, moderate in glacial meltwater and low in clean ice (debris-poor) and snow. Principal component analysis was applied to the resulting dataset and could be performed in-field to rapidly aid the allocation of resources for further sample analysis. We anticipate that in-field data collection will allow for multiple rounds of sampling, analysis, interpretation and refinement within a single field campaign, resulting in the collection of larger and more appropriate datasets, ultimately with more efficient science return.
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    Distinct respiratory responses of soils to complex organic substrate are governed predominantly by soil architecture and its microbial community
    (Elsevier, 2016-10-13) Fraser, Fiona; Todman, L. C.; Corstanje, Ronald; Deeks, Lynda K.; Harris, Jim A.; Pawlett, Mark; Whitmore, A. P.; Ritz, Karl
    Factors governing the turnover of organic matter (OM) added to soils, including substrate quality, climate, environment and biology, are well known, but their relative importance has been difficult to ascertain due to the interconnected nature of the soil system. This has made their inclusion in mechanistic models of OM turnover or nutrient cycling difficult despite the potential power of these models to unravel complex interactions. Using high temporal-resolution respirometery (6 min measurement intervals), we monitored the respiratory response of 67 soils sampled from across England and Wales over a 5 day period following the addition of a complex organic substrate (green barley powder). Four respiratory response archetypes were observed, characterised by different rates of respiration as well as different time-dependent patterns. We also found that it was possible to predict, with 95% accuracy, which type of respiratory behaviour a soil would exhibit based on certain physical and chemical soil properties combined with the size and phenotypic structure of the microbial community. Bulk density, microbial biomass carbon, water holding capacity and microbial community phenotype were identified as the four most important factors in predicting the soils’ respiratory responses using a Bayesian belief network. These results show that the size and constitution of the microbial community are as important as physico-chemical properties of a soil in governing the respiratory response to OM addition. Such a combination suggests that the 'architecture' of the soil, i.e. the integration of the spatial organisation of the environment and the interactions between the communities living and functioning within the pore networks, is fundamentally important in regulating such processes.
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    Effect of different organic amendments on actual and achievable yields in a cereal-based cropping system
    (Springer, 2023-02-27) Albano, Xavier; Whitmore, Andrew P.; Sakrabani, Ruben; Thomas, Cathy L.; Sizmur, Tom; Ritz, Karl; Harris, Jim A.; Pawlett, Mark; Watts, Chris; Haefele, Stephan M.
    Soil fertility is at risk in intensive cropping systems when using an exclusive regime of inorganic fertilisers without returning sufficient organic matter to the soil. Our objective was to evaluate the long-term effects of commonly used organic amendments interacting with different rates of inorganic nitrogen fertiliser on crop yields of winter wheat. Yield data from winter wheat were collected for five seasons between 2013 and 2019 from a continuous field trial based at Rothamsted Research, SE England. Organic amendments (anaerobic digestate, compost, farmyard manure, and straw at a rate of 0 and 2.5 ton C per hectare) and five rates of inorganic nitrogen fertiliser (NH4NO3 at 0, 80, 150, 190, 220 kg N ha−1) were applied to winter wheat grown in an arable rotation. At the same inorganic N rate, grain yields for the different organic amendment treatments (excluding the straw treatment) were statistically similar but significantly greater than the unamended control treatment. The nitrogen rate required for optimum yields tended to be lower in plots receiving a combination of organic amendments and mineral fertiliser. Based on the observed and modelled response functions, organic amendments excluding straw increased maximum achievable yields compared to non-amended controls. The size of the effect varied between seasons and amendments (+4.6 to +19.0% of the control yield), increasing the mean maximum achievable yield by 8.8% across four seasons. We conclude that the application of organic amendments can increase the yield potential in winter wheat substantially over what is achievable with inorganic fertiliser only.
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    Effects and influence of the urea component of an organomineral fertiliser on phosphorus mineralisation in a low-P index arable and grassland soil
    (Cranfield University, 2016) Abubakar, Musa Ahmad; Sakrabani, Ruben; Pawlett, Mark
    Addition of organic waste such as sewage sludge (biosolids) has been recognised as one of the cost effective method of waste recycling practice of maintaining levels of organic matter in agriculture. Biosolids are a slow-release nutrient (N and P) which also improves soil physical and microbiological properties and as such offer a promising plant nutrient with less impact on soil than mineral fertilisers. Implementation of wastewater treatment directive 91/271//EC has caused large amount of sewage sludge production and availability. Hence, management of biosolids to provide available phosphorus through soil recycling would reduce reliance on finite rock phosphates (over 85% P-fertilisers) extraction, protect or minimise environmental problems such as eutrophication and also help the resource-limited farmers particularly in developing countries, to mitigate P-fertiliser limitation in the soil. More awareness of the impact of different agricultural fertiliser management practices on soil quality and sustainability has led to more interest of combining organic residuals with inorganic fertilisers to prevent further fertility decline and degradation of soil. Amongst recent nutrient integration, was the nutrient-balanced sludge-based (biosolids with urea and potash) called organomineral fertiliser (OMF), which shows agronomic efficiency of phosphorus management when applied to the field crops such as winter wheat. However, to manage phosphorus mineralisation effectively in the organomineral fertiliser treated soil, it is important to understand the effects of urea components in OMF during mineralisation of phosphorus in soil. This research aimed to understand the influence that the urea component of an organomineral fertiliser (OMF) has during phosphorus mineralisation in soil. Therefore urea granules were grounded into powdered form and mixed with grounded biosolids pellets as a source of phosphorus to obtain organomineral fertilisers. This whole research included two different control soil incubation experiments (1a & 1b) both observed over a 60 days period. Incubation experiment 1a (involved mixing various rates of biosolids and urea in soil) had two different soil samples from the grassland (sandy clay loam) and arable (clay loam) sites. In terms of initial soil phosphorus content, the grassland and arable soils are classified as P-index 1 and 2 respectively. Soil samples were analysed for pH, mineralisable nitrogen (NH4 + , NO3 - ), available phosphorus, microbial biomass carbon and phosphorus and phospholipids fatty acids profiles during 0, 6, 15, 20, 35, 45 and 60 days incubation period. While in the incubation experiment 1b (mixing different rates of urea with fixed quantity of biosolids in soil), soil from the same grassland, were being sampled at 10 day intervals (10, 20, 30, 40, 50, and 60) after taking the initial sample of day 0 and analysed for pH, mineralisable P and phosphomonoesterase enzyme activities. The incubation experiments showed that, mineralisation of available phosphorus were significantly (p<0.001) higher in the biosolids and organomineral (OMF) fertiliser treated soils compared to control during 20 and 30 days period. The mean values of mineralisable P from OMF treatment for the incubation experiment 1a were 14.5 and 19.5 mg/kg in the grass and arable soils respectively. The mineralisation rates of biosolids-P from organomineral fertiliser (OMF) amended soils were also reduced significantly, as the dosages of urea component were increased according to the 50, 150 and 250Kg/N equivalents during the 60 days incubation experiment 1b. The mean available P values from the OMF amendments were 28.0, 25.7 and 23.4mg/kg respectively; according to the increasing amount of urea content at 50, 150 and 250Kg/N equivalents respectively. The overall trend of organomineral fertiliser phosphorus (OMF-P) mineralisation rate have shown significant (p<0.001) reduction with increased doses of urea components, with the fixed biosolids equivalent rate of 250Kg/ha during the incubation experiment 1b. There were no significant (p>0.01) changes in pH from both soil incubation experiment 1a and 1b, except for the urea only treated samples at the 250KgN/ha equivalent rate from the sandy clay loam grassland soil, which shows up to 1 unit increase (pH=8.1) compared to other treatments, just a day after kick-starting the incubation experiment, but eventually becomes reduced to the original pH (6.9) during the incubation period. Microbial community change in both arable and grassland soil from initial day zero showed distinct and consistent shifts in trends through the 20 and 45 days respectively, irrespective of their treatments, and then gradually shifted towards the original starting point at the final incubation study of day 60. This was however attributed to the function of change with time, since it could not be categorically assigned to the OMF application effects only, but perhaps community change effects with time could be the main factor. Even though there was no any important patterns or trends observed between the indigenous treatments, but the wide spreading and shift distances amongst treatments during 20 and 45 days were higher compared to the 0 and 60 days, and this is probably because there were more phosphorus mineralisation when microorganisms were able to access more dissolved organic carbon as shown by high biomass carbon during 20 and 35 days incubation time, and utilise it to generate energy that kept them more active within those period before it gradually becomes exhausted, since there was no external source of energy being added. Similarly, phosphomonoesterase enzyme activities in the soil treatments except for the urea only amended samples, showed significant (p<0.01) differences between days 20, 30 and 40 compared to days 0, 50 and 60 and the phosphatase activities in the OMF amendments had significantly higher acid than alkaline phosphatase activities. Organomineral phosphorus (OMF-P) mineralisation in soil during 60 days incubation in this short-term study have shown potential P release in both soils, and the OMF-P mineralisation rate was highest in the formulation having fixed biosolids with urea at 150KgN/ha equivalent compared to other formulations (50KgN/ha and 250KgN/ha) and therefore effects of urea component of the organomineral fertiliser is an important factor when considering OMF as a promising P alternative or source in low-P soil during phosphorus management. Appropriate product formulation depending on the crop needs is therefore very important for soil phosphorus nutrient management and sustainability.
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    The effects of a thermal conditioning treatment forweed control upon soil biological properties
    (Cranfield University, 2009-09) Amis, K. S.; Ritz, Karl.; Pawlett, Mark
    Weeds, and their associated control, are often significant in limiting production within organic farming due to restrictions on herbicide use within such systems. Organic farmers rely on alternative weed control methods, including soil thermal treatments. Preliminary research has shown soil steaming to be a potentially effective weed control method, but procedures have yet to be fully explored and implemented. One issue is the effect steam treatment has upon the non-targeted components of the soil system. This study considered the magnitude and persistence of the effects that soil steaming had on biological aspects of soil systems within the organic production of Daucus carota, sativus (L) (carrots). A field-based study was conducted whereby soil treated with steam was sampled at intervals of 1 hour, and 14 and 42 days following treatment. Impacts upon the soil system were then assessed by measuring a range of chemical and biological properties related to carbon and nitrogen cycling. Immediately following steaming, actual nitrification was inhibited with an associated accumulation of ammonium-N, displaying an initial low resistance to the thermal treatment. However, recovery of this process was apparent at approximately 14 days post-treatment with a significant rise in both nitrate-N and potential nitrification, indicating a degree of resilience of the nitrification process. Overall, other measured components of the soil system, including microbial activity and organic carbon, also demonstrated signs of resilience, indicating that the system still had the ability to function and provide its regulatory and provisioning services within the short-term following soil steaming treatment.
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    Effects of hotter, drier conditions on gaseous losses from nitrogen fertilisers
    (Elsevier, 2023-07-26) Drame, Marieme; Carswell, Alison; Roberts, William; Hood, Jess; Jemo, Martin; Heuer, Sigrid; Kirk, Guy; Pawlett, Mark; Misselbrook, Tom
    Global warming is expected to cause hotter, drier summers and more extreme weather events including heat waves and droughts. A little understood aspect of this is its effects on the efficacy of fertilisers and related nutrient losses into the environment. We explored the effects of high soil temperature (>25 °C) and low soil moisture (<40% water filled pore space; WFPS) on emissions of ammonia (NH3) and nitrous oxide (N2O) following application of urea to soil and the efficacy of urease inhibitors (UI) in slowing N losses. We incubated soil columns at three temperatures (15, 25, 35 °C) and three soil moisture contents (20, 40, 60% WFPS) with urea applied on the soil surface with and without UIs, and measured NH3 and N2O emissions using chambers placed over the columns. Four fertiliser treatments were applied in triplicate in a randomised complete block design: (1) urea; (2) urea with a single UI (N-(n-butyl) thiophosphoric triamide (NBPT); (3) urea with two UI (NBPT and N-(n-propyl) thiophosphoric triamide; NPPT); and (4) a zero N control. Inclusion of UI with urea, relative to urea alone, delayed and reduced peak NH3 emissions. However, the efficacy of UI was reduced with increasing temperature and decreasing soil moisture. Cumulative NH3 emission did not differ between the two UI treatments for a given set of conditions and was reduced by 22–87% compared with urea alone. Maximum cumulative NH3 emission occurred at 35 °C and 20% WFPS, accounting for 31% of the applied N for the urea treatment and 25%, on average for the UI treatments. Urease inhibitors did not influence N2O emissions; however, there were interactive impacts of temperature and moisture, with higher cumulative emissions at 40% WFPS and 15 and 25 °C accounting for 1.85–2.62% of the applied N, whereas at 35 °C there was greater N2O emission at 60% WFPS. Our results suggest that inclusion of UI with urea effectively reduces NH3 losses at temperatures reaching 35 °C, although overall effectiveness decreases with increasing temperature, particularly under low soil moisture conditions.
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    Effects of organic matter additions on the soil microbial population and associated stoichiometry in horticultural systems.
    (Cranfield University, 2023-01) Hasler, Rachel; Pawlett, Mark; Harris, Jim A.
    Organic matter addition influences soil function (respiration/ decomposition) and community structure (PLFA/ NLFA community profiles) which result in changes to the provision of soil derived ecosystem services. Additions of organic matter to gardens (e.g. composts, mulches, soil conditioners) is a widespread practice both globally and in the UK. Research on the long-term cumulative impact of annual additions to UK gardens is limited. A field trial, set-up in 2007, at the Royal Horticultural Society’s Wisley Gardens site, was used to examine the changes to soil chemical, physical and biological soil quality indicators following 12 years of different soil organic matter additions. Additions varied in carbon-to-nitrogen ratios (C/N), physical structure and macro/ micro-nutrient profiles. The amendments used in the trial included composted bark, bracken, stable manure, garden compost, spent mushroom growing compost, peat, fertiliser (rate adjusted each year to meet plant growth requirements) and controls; no organic matter addition and no plant sown, no organic matter addition and plant sown. Lab studies were designed following analyses of amendment legacy effects in field trial plots to further examine the effects of addition on microbiological indicators of soil function, health and quality. Reviewing long term chemical and physical data from the field trial highlighted significant effects of organic matter additions on soil micro- and macro-nutrients. Recommendations for garden industry were made from the findings and include the need for labelling standards for compost material packaging to reduce unwanted environmental impacts of use. Organic matter treatment to clay-loam textured soil significantly increased microbial respiration and shifted microbial community structure. The effects were distinct and dependent on composition of the organic matter applied. The horticultural sector has outlined targets for reducing the impact of garden practise on drivers of climate change. This study aligns with literature which seeks to understand common practise in order to improve economic and environmental sustainability.
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    Efficacy of bioadmendments in reducing the influence of salinity on the bioremediation of oil-contaminated soil
    (Elsevier, 2023-06-16) Atai, Emmanuel; Jumbo, Raphael; Cowley, Tamazon; Azuazu, Ikeabiama; Coulon, Frederic; Pawlett, Mark
    This study aimed to investigate the potential of three bioamendments (rice husk biochar, wheat straw biochar, and spent mushroom compost) to enhance microbial degradation of crude oil in saline soil. A soil microcosm experiment was conducted, comparing the response of soil microorganisms to crude oil under saline (1 % NaCl) and non-saline conditions. The soils were amended with different bioamendments at varying concentrations (2.5 % or 5 %), and degradation rates were monitored over a 120-day period at 20 °C. The results showed that the bioamendments significantly influenced the degradation of total petroleum hydrocarbons (TPH) in both non-saline and saline soils by 67 % and 18 % respectively. Non-saline soils exhibited approximately four times higher TPH biodegradation compared to saline soils. Among the bioamendments, rice husk biochar and spent mushroom compost had the greatest impact on biodegradation in saline soil, while wheat straw and rice husk biochar combined with spent mushroom compost showed the most significant effects in non-saline soil. The study also revealed that the bioamendments facilitated changes in the microbial community structure, particularly in the treatments with rice husk biochar and wheat straw biochar. Actinomycetes and fungi were found to be more tolerant to soil salinity, especially in the treatments with rice husk biochar and wheat straw biochar. Additionally, the production of CO2, indicating microbial activity, was highest (56 % and 60 %) in the treatments combining rice husk biochar or wheat straw biochar with spent mushroom compost in non-saline soil, while in saline soil rice husk biochar treatment (50 %) was the highest. Overall, this research demonstrates that the application of bioamendments, particularly rice husk biochar and wheat straw biochar combined with spent mushroom compost, can effectively enhance the biodegradation of crude oil in saline soil. These findings highlight the potential of such bioamendments as green and sustainable solutions for soil pollution, especially in the context of climate change-induced impacts on high-salinity soils, including coastal soils.
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    Engineering difference: Matrix design determines community composition in wastewater treatment systems
    (Elsevier Science B.V., Amsterdam., 2012-03-01T00:00:00Z) Harris, Jim A.; Baptista, J. D. C.; Curtis, T. P.; Nelson, A. K.; Pawlett, Mark; Ritz, K.; Tyrrel, Sean F.
    There is a growing view that the application of ecological theory has the potential to facilitate a transition from a descriptive to a predictive framework in wastewater engineering. In this study we tested the hypotheses that: (i) it is possible to engineer consistent differences between microbial communities in wastewater treatment modules; (ii) there is a positive relationship between structural complexity and genetic diversity; (iii) such interactions are modulated by the availability of energy. We developed four treatment modules of increasingly complex support material (matrix) design, and pumped a synthetic wastewater through them for 16 weeks. We then disassembled the modules and assessed the phylogenetic (general eubacteria and ammonium diversity of the communities present on the support materials. We found that different genotypic and phenotypic community structures were reliably generated by the engineering of their physical environment in terms of structural complexity (as determined by particle size distribution and therefore pore size distribution). Furthermore, there was a notably consistent response of the phenotypic structure to such circumstances, and also to the presence of organic matter. However, we found no significant relationships between genetic diversity and structural complexity either for eubacterial or ammonia-oxidiser microbial groups. This work demonstrates that is it possible to engineer modules of differing microbial community composition by varying their physical complexity. This is an essential first step in testing relationships between system diversity and treatment resilience at a process level.oxidisers, by DGGE profiling) and phenotypic (by PLFA profiling)
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    Estimating soil organic matter: a case study of soil physical properties for environment-related issues in southeast Nigeria
    (2021-10-17) Ofem, Kokei Ikpi; John, Kingsley; Pawlett, Mark; Eyong, Michael Otu; Awaogu, Chukwuebuka Edwin; Umeugokwe, Pascal; Ambrose-Igho, Gare; Ezeaku, Peter Ikemefuna; Asadu, Charles Livinus Anija
    The different deposition periods in sedimentary geological environment have made the build-up and estimation of soil organic matter ambiguous to study. Soil organic matter has received global attention in the ambience of international policy regarding environmental health and safety. This research was to understand the inter-relationship between soil organic matter and bulk density, saturated hydraulic conductivity (Ksat), total, air-filled and capillary porosities for organic matter estimation, via different multiple linear regression functions (i.e., leapbackward, leap forward, leapseq and lmStepAIC), in soils developed over the sedimentary geological environment. Eight mapping units were obtained in Ishibori, Agoi Ibami and Mfamosing via digital elevation model. Two pits were sited within each mapping unit, and 53 soil samples were used for the study. In soils over shale–limestone–sandstone, two pits were sited, six in alluvium, four in sandstone–limestone and four in limestone. Overall correlation between SOM with Ksat (r = 0.626) and BD (r = − 0.588) was significant (p < 0.001). The strongest correlation was obtained for SOM with BD (r = − 0.783) and Ksat (r = 0.790) in soils over limestone. In contrast, soils over shale–limestone and sandstone geological environment gave the weakest relationship (r < 0.6). Linear regression gave a similar prediction output. The best performing was leapbackward (RMSE = 11.50%, R2 = 0.58, MAE = 8.48%), which produced a smaller error when compared with leap forward, leapseq and lmStepAIC functions in organic matter estimation. Therefore, we recommend applying leapback linear regression when estimating soil organic variation with physical soil properties for solving soil–environmental issues towards sustainable crop production in southeast Nigeria.