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Under climate change and local and global food security pressures conversion to agricultural lands on Podzols developed under boreal forests is accelerating across the global north. After conversion Podzols, acid and sandy, are infertile requiring significant management to allow economic production. Biochar, while less useful on fertile soils, may accelerate fertility gains on such marginal lands; it is already considered or land-applied by local farmers, under minimal guidance. A multi-year experiment assessed the utility of single or split application of biochar (BC), and of BC doses, for beet yields and nutrient uptake on newly converted Podzols. Time and rate-dependent progression of yields, macro- and micro-nutrients uptake, all parameters identified of interest by northern farmers, were evaluated. Kiln-derived hardwood biochar was added at 0, 10, 20, 40 or 80 Mg BC-C ha−1 (BC 0 to 80) either as single or as double application. Beet yields and elemental compositions were assessed over 4 years after biochar application. Work was done on a private farm in Labrador, Canada, under a scenario relevant to the boreal north. BC 0 could not sustain significant crop growth, suggesting that post-conversion mineralization of residual soil organic matter cannot support plant growth. In the first one to three years after application of biochar yields increased above the control, but statistically independent of application rates. A statistically significant positive biochar-rate to yield dependency was verifiable only in year 4. Nevertheless, biochar's positive effect on yields declined with time after application: e.g., BC 10 matched BC 0 yields in year 4. For the first three years, root nitrogen (N) concentrations were inversely correlated to yields and plant N% declined with biochar rate. In year 4 plant N% was directly correlated to plant biomass. In general, partitioning of nutrients between beet leaves and roots was not discernibly affected by the rate of biochar; an exception was boron whose preferential accumulation in leaves was directly related to the rate of biochar, indicating a role for the biochar for its mobilization. Biochar had an immediate positive effect on the beet yields and affected plant stoichiometry. Initially this was independent of the biochar rate. Biochar's utility declined with time at a rate inversely related to its application rate. Biochar is a recommendable fertility management tool for infertile, newly converted boreal Podzols; rates in the range of 10 Mg BC-C ha-1 may be repeated annually or every few years as practically feasible. Long term utilization requires further monitoring of micronutrients availability and uptake to inform any necessary management adjustments. Fertilizer management must consider the time since biochar's addition to soil. • Unmanaged Podzols on freshly converted boreal forest are infertile. • Biochar addition increases beet yield and yield quality, initially rate-independent. • A rate-dependent impact of biochar on yields and yield quality was noted in year 4. • Biochar's benefit fades over time at a rate inverse to its application rate. • Repeated, small biochar doses are recommendable over large single applications. [ABSTRACT FROM AUTHOR]

The spatial variability in soil physical and hydraulic properties for a managed podzol was assessed using soil apparent electrical conductivity (ECa). Two EMI sensors, the multi-coil (MC) and multi-frequency (MF), were adopted for measurement of ECa on a silage- corn experimental plot in western Newfoundland, Canada. Results demonstrated a significant relationship between the ECa mean relative differences (MRD) and the soil moisture content MRD (R2 = 0.33 to 0.70) for both MC and MF sensors. The difference in depth sensitivity between MC and MF sensors accounted for the variation (0.015 to 0.09) in ECa standard deviation of the relative differences. A significant linear relationship was found between the ECa MRD and sand (R2 = 0.35 and 0.53) or silt (R2 = 0.43), but not with clay (R2 = 0.06 and 0.16). The spatial variability of the ECa-based predictions (CV = 3.26 to 27.61) of soil properties was lower than the measured values (CV = 5.56 to 41.77). These results inferred that the temporal stability of ECa might be a suitable proxy to understand the spatial variability of soil physical and hydraulic properties in agricultural podzols. [ABSTRACT FROM AUTHOR]

Plant clusters govern soil microbiology in desert systems. Female Acanthosicyos horridus plants in the Namib Desert are preferentially accessed by grazers, especially during fruit availability. We hypothesized that this differential grazing affects the taxonomic diversity of soil bacterial populations. Sampling was carried out at three locations on a northwest-to-southeast transect starting at the Kuiseb Delta, near the shores of the Atlantic in the western Namib Desert, and extending inland over a distance of 140 km. Analyses of the soil samples showed that proximity to the sea had a strong impact on soil salinity. Soil pH and organic matter content were generally not significantly correlated with the presence or absence of plants and varied little and non-uniformly along the transect. A. horridus presence led to distinct under-canopy bacterial-community diversity in contrast with the non-vegetated spaces between shrubs. However, plant gender has only a marginal, statistically insignificant impact on the bacterial-diversity properties, thus not supporting our hypothesis. Therefore, the taxonomic diversity of the bacterial community in Namib Desert soils vegetated with A. horridus is primarily governed by the presence or absence of plants and by proximity to the ocean. [ABSTRACT FROM AUTHOR]

Highlights • Human trampling on soil biota and abiota in Oulanka Natural Reserve was evaluated. • Soil compaction affected functional and taxonomic diversity of microbial communities. • Physicochemical features of soil were governed by the extreme abiotic environment. Abstract Functional and taxonomic diversities of microbial communities in Arctic soils are governed by the extreme abiotic environment and affected by human activities. We assessed the impact of trampling by humans on biotic and abiotic parameters relevant to soil health at the Kiutaköngäs Trail, Oulanka Nature Park, Finland. Soil was sampled from the 0 to 2 cm, 2 to 5 cm, and 5 to 10 cm layers for four levels of trampling pressure: heavily trampled, medium trampled, low trampled sites, and non-trampled control. Measured and estimated abiotic soil parameters included organic matter, pH, water-holding capacity, and bulk density for each soil sample. Biotic parameters included determination of microbial biomass, CO 2 evolution and MicroResp®-based community level physiological profiles, and as well as bacterial taxonomic diversity. Results have shown that total organic matter amount might not change significantly under trampling. Nevertheless, absolute substrate utilization, functional diversity, and respiration varied with depth, significantly declining in the immediate subsurface under the trampled sites. On the other hand, the most extreme stress associated with the greatest trampling intensity was associated with an increase in taxonomic diversity but with a proportional decline in Acidobacteria abundance, in line with the increase in pH. [ABSTRACT FROM AUTHOR]

Food webs and the functional status of soils are governed primarily by microbial carbon and nitrogen fluxes as determined by ecosystem type and management. In boreal regions, expanding and intensifying agriculture affects the functional status of soils due to biodiversity, carbon, and nitrogen losses. The status of northern soils must be monitored using informative, standardised methods that are comparable across land uses, managements, and scales. Food web nodes sensitive to complex changes in the soil environment, such as free-living nematodes, can be utilised to monitor alterations in the functional state of natural systems and inform management decisions to ensure that new and established agriculture is environmentally sustainable. The objectives of this a-priori review were to 1) describe the likely impacts of land use and land use change on nematode communities and indices in boreal regions, 2) determine if nematodes respond differently to land use and land use change in the global biomes, and 3) identify literature gaps related to nematodes in the boreal biome to draw attention to future research needs. Soil quality bioindicators were compared and 31 published, peer-reviewed, in-situ studies found in Web of Science and Scopus databases in March 2020 that assessed the impacts of land use and land use change on free-living nematode parameters across global biomes were systematically summarised. While the northern biomes have greater abundances of nematodes than other biomes, the literature search found zero articles pertaining to nematodes in boreal or Arctic agricultural systems highlighting the need for future work. Given the key roles that free-living nematodes have in the food web, their longer and more stable generation times than microbes, and relatively well-known taxonomy, life history traits, and feeding habits, the authors propose that nematodes could and ought to be employed as indicators of functional changes in boreal agricultural soils. [Display omitted] • New and existing boreal agriculture must be monitored for sustainability. • Bioindicators can support management decisions pertinent to soil functions. • Nematode assessments are reliable, cheap, and accessible. • Literature on free-living nematode from boreal and arctic ecosystems is limited. [ABSTRACT FROM AUTHOR]

Microbial function, composition, and distribution play a fundamental role in ecosystem ecology. The interaction between desert plants and their associated microbes is expected to greatly affect their response to changes in this harsh environment. Using comparative analyses, we studied the impact of three desert shrubs, Atriplex halimus (A), Artemisia herba-alba (AHA), and Hammada scoparia (HS), on soil- and leaf-associated microbial communities. DNA extracted from the leaf surface and soil samples collected beneath the shrubs were used to study associated microbial diversity using a sequencing survey of variable regions of bacterial 16S rRNA and fungal ribosomal internal transcribed spacer (ITS1). We found that the composition of bacterial and fungal orders is plant-type-specific, indicating that each plant type provides a suitable and unique microenvironment. The different adaptive ecophysiological properties of the three plant species and the differential effect on their associated microbial composition point to the role of adaptation in the shaping of microbial diversity. Overall, our findings suggest a link between plant ecophysiological adaptation as a 'temporary host' and the biotic-community parameters in extreme xeric environments. [ABSTRACT FROM AUTHOR]

Changes in the soil labile C pools induced by vegetation rehabilitation on semiarid lands are assumed to correlate with changes in the microbial catabolic profiles. To verify this, soil was sampled under the canopies of 12-year-old (R12Y) and 30-year-old (R30Y) planted Caragana microphylla shrubs, as well as native C. microphylla shrubs, all located in the Horqin Sandy Land, China. Community Level Physiological Profiles (CLPPs) of soils were determined to reveal any qualitative and quantitative shifts in soil microbial catabolism linked with the revegetation process. water-soluble C (WSC) and hot-water extractable C (HWEC) were measured to indicate the availability of labile C pools. As the restoration proceeds, soil organic C (C org ) increased 2–3 times at the R30Y habitat compared to the R12Y habitat. The total utilization rate of the 15 C substrates also increased from 0.68 μg CO 2 -C g −1 soil h −1 at the R12Y habitat to 4.90 μg CO 2 -C g −1 soil h −1 at the R30Y habitat, but a slight decline in catabolic diversity, from 2.53 to 2.29, was recorded. Principal component analysis and redundancy analysis revealed that soil microbial communities colonizing the R12Y habitat exhibited an affinity to carbohydrates, which positively correlated to the relative concentration of WSC. Those colonizing the R30Y and native habitats mainly preferred carboxylic acids and 3,4-dihydroxybenzoic acid due to higher C org content and relative concentration of HWEC. [ABSTRACT FROM AUTHOR]

Quantitative viral risk assessments for wastewaters are notoriously difficult. The often considered quantitative reverse transcriptase PCR reflects poorly on virus infectivity rates leading to inaccurate risk interpretations. Various techniques focused on the degradation of the nucleic acids of non-infective viruses were previously employed. We comparatively assessed the effectiveness of such enzymatic treatments for MS2 bacteriophage in treated wastewaters. The single use of RNase A at an appropriate concentration may be as effective as the combination of RNase followed by Proteinase K and more rapid. While all tested enzymatic treatments minimized recovery of RNA (>95 %) in the absence of infective MS2, none completely eliminated the signal recovery. Selection of any enzymatic protocol for minimizing recovery of RNA from degraded, non-infective viruses should balance the methods efficacy with its expediency. [ABSTRACT FROM AUTHOR]

In xeric environments, organic carbon is provided by above and belowground plant-litter components. The plants also act as an aboveground physical barrier. Both these biotic and abiotic features contribute to ‘fertile-island’ formation. Fifty Hammada scoparia shrubs and 50 artificial plants were randomly marked at a study site. The latter allowed simulation of the physical (abiotic) impact of perennial-plant cover and thus allowed distinguishing between biotic and strictly abiotic impacts on under-canopy soil bacterial diversity in a desert ecosystem. Soils were collected monthly over one year from under canopies of H. scoparia and artificial plants, and from the control area between the shrubs. The presence or absence of real plants and seasonality was the main drivers of bacterial diversity in soils. Simple canopy cover, as offered by the artificial plants, induced non-significant shifts in the diversity of the dominant bacteria. [ABSTRACT FROM AUTHOR]

Standard protocols for monitoring wastewater treatment efficacy target Escherichia coli and fecal coliforms. This might not accurately describe risks associated with antibiotic resistance in the bacterial population of treated wastewaters. We modified a standard agar recovery method by amending it with various antibiotics. The resulting bacterial colonies were submitted to 454 pyrosequencing; thus we identified the diversity of culturable antibiotic resistant bacteria from treated and raw wastewaters. This approach produced 209,706 high quality reads of >300 bp. Operational taxonomic units (OTUs) within Proteobacteria dominated the system. The Shannon-Wiener H' index showed bacterial populations recovered on ciprofloxacin amended agars to be the least diverse. Principal component analysis of OTU distribution at phylum level showed that Proteobacteria accounted for most of the variability. The same analysis revealed most of the samples to have similar diversities at phylum level being dominated by Proteobacteria, though a few samples, typically recovered from ciprofloxacin or doxycycline amended agars were often dissimilar. Arcobacter spp. or E. coli were dominant in the bacterial communities recovered on agars amended with ciprofloxacin or doxycycline, respectively. Genera containing putative pathogens were mostly representatives of Gamma and Epsilon proteobacteria. Bacterial populations containing multiple antibiotic resistance (MAR) in the final treated effluent was a possibility. [ABSTRACT FROM AUTHOR]

Water and nutrient availability are the major limiting factors of biological activity in arid and semiarid ecosystems. Therefore, perennial plants have developed different ecophysiological adaptations to cope with harsh conditions. The chemical profile of the root exudates varies among plant species and this can induce variability in associated microbial populations. We examined the influence of two shrubs species, Artemisia sieberi and Noaea mucronata, on soil microbial diversity. Soil samples were collected monthly, from December 2006 to November 2007, near canopies of both shrubs (0-10-cm depth). Samples were used for abiotic tests and determination of soil bacterial diversity. No significant differences were found in the abiotic variables (soil moisture, total organic matter, and total soluble nitrogen (TSN)) between soil samples collected from under the two shrubs during the study period. No obvious differences in the Shannon-Weaver index, evenness values, or total phylogenetic distances were found for the soil microbial communities. However, detailed denaturing gradient gel electrophoresis (DGGE) clustering as well as taxonomic diversity analyses indicated clear shifts in the soil microbial community composition. These shifts were governed by seasonal variability in water availability and, significantly, by plant species type. [ABSTRACT FROM AUTHOR]

Microbial diversity associated with micropropagated Atriplex species was assessed using microscopy, isolate culturing, and sequencing. Light, electron, and confocal microscopy revealed microbial cells in aseptically regenerated leaves and roots. Clone libraries and tag-encoded FLX amplicon pyrosequencing (TEFAP) analysis amplified sequences from callus homologous to diverse fungal and bacterial taxa. Culturing isolated some seed borne endophyte taxa which could be readily propagated apart from the host. Microbial cells were observed within biofilm-like residues associated with plant cell surfaces and intercellular spaces. Various universal primers amplified both plant and microbial sequences, with different primers revealing different patterns of fungal diversity. Bacterial and fungal TEFAP followed by alignment with sequences from curated databases revealed 7 bacterial and 17 ascomycete taxa in A. canescens, and 5 bacterial taxa in A. torreyi. Additional diversity was observed among isolates and clone libraries. Micropropagated Atriplex retains a complex, intimately associated microbiome which includes diverse strains well poised to interact in manners that influence host physiology. Microbiome analysis was facilitated by high throughput sequencing methods, but primer biases continue to limit recovery of diverse sequences from even moderately complex communities. [ABSTRACT FROM AUTHOR]

Land application of organic wastes can lead to contamination of ground- and surface waters. The pathway taken by particulate contaminants, such as microorganisms, is entirely dependent on the partitioning of the incoming rain or irrigation water. The soil hydraulic properties are critical in determining the infiltration:runoff water-partitioning ratio. Components of the land applied organic waste can modify the soil hydraulic properties and thus alter this ratio. It was shown that liquid manure impacted matrix and macropore flow differently; favouring the later through obstruction of the former. In contrast solid manure favoured matrix flow over macropore flow thereby increasing the water storage in soil, which tended to reduce the likelihood of runoff. The relationships between soil hydraulic conductivity and soil textural and structural properties in repacked soil columns was unrelated to the relationships obtained for the same soils maintained in their natural undisturbed field state. [ABSTRACT FROM AUTHOR]

We evaluated the impact of the manure type used in soil-manure mixtures on the detection of culturable E. coli as tested in water quality monitoring. A series of incubation experiments, lasting up to 200 d, allowed evaluation of the potential impact of manure X soil interactions on the augmentation of culturable E. coli. Two soil types (sandy loam and a silt loam), two manure types (liquid swine manure and solid beef cattle manure), and three temperature levels (4, 12, and 20°C) were investigated. The significance of the presence of competing microorganisms was estimated by comparing results from manure mixtures with sterile and nonsterile soils. Water content in the soil-manure mixtures was maintained close to field capacity to eliminate the specific impact of water availability. We found that culturability of the indicator organism, E. coli, changed with time and was dependent on the type of manure used and its interaction with soil. Escherichia coli could be cultured for a longer time from soils with liquid manure additions. Whereas E. coli numbers were initially higher from soils treated with solid beef cattle manure, their numbers decreased more rapidly and the duration of their apparent survival was shorter. Resilience of culturable E. coli was independent of their initial numbers in manure. [ABSTRACT FROM AUTHOR]

Survival and transport of pathogens from manure in the environment depend on a number of complex phenomena. An important question is how the properties of such a complex environment as the soil–manure medium impact the persistence of bacteria within the vadose zone. First, manure can change the partitioning of precipitation water between infiltration (enhanced by solid manure) and surface runoff (stimulated by liquid manure). Components of manure, such as straw and coarse organic matter, can strain and filter micro-organisms from the transporting water. After infiltrating the soil, the retention of bacteria depends on the physical configuration of soil, the soil chemistry, and the properties of the microbial cells. Transport of bacteria in soils obeys the general laws pertinent to macropore flow and the interaction between particles and surfaces of variable charge. Detailed characterisation of the variable properties within the structured soil profile is a difficult task. Application of manure can result in significant changes in the physical and electrochemical properties of the soils and microbial cells. Such changes can affect the interaction between bacterial cells and soils in several ways: increase filtration, modify the kinetics of the physico-chemical interactions between charged surfaces, and alter the competition for retention sites between suspended soluble and particulate compounds. Survival of faecal bacteria is affected by the physical and chemical conditions existing prior to manure application as well as by conditions imposed by mixing soil and manure. Competitive interaction with native soil bacteria, in the soil–manure mixtures, is an important aspect governing survival of introduced organisms. [Copyright &y& Elsevier]

Laboratory batch tests indicate that addition of sterile municipal sewage biosolids to clay soil from four depths increases the numbers of Escherichia coli isolates recoverable in EC-MUG broth (EC broth with 4-methylumbelliferyl-β-glucuronide). This effect was most marked for the deeper soil layers, with increases of about 2.6 orders of magnitude in E. coli most probable number. [ABSTRACT FROM AUTHOR]

Precision agriculture (PA) involves the management of agricultural fields including spatial information of soil properties derived from apparent electrical conductivity (ECa) measurements. While this approach is gaining much attention in agricultural management, farmed podzolic soils are under-represented in the relevant literature. This study: (i) established the relationship between ECa and soil moisture content (SMC) measured using time domain reflectometry (TDR); and (ii) evaluated the estimated SMC with ECa measurements obtained with two electromagnetic induction (EMI) sensors, i.e., multi-coil and multi-frequency, using TDR measured SMC. Measurements were taken on several plots at Pynn's Brook Research Station, Pasadena, Newfoundland, Canada. The means of ECa measurements were calculated for the same sampling location in each plot. The linear regression models generated for SMC using the CMD-MINIEXPLORER were statistically significant with the highest R2 of 0.79 and the lowest RMSE (root mean square error) of 0.015 m3 m−3 but were not significant for GEM-2 with the lowest R2 of 0.17 and RMSE of 0.045 m3 m−3; this was due to the difference in the depth of investigation between the two EMI sensors. The validation of the SMC regression models for the two EMI sensors produced the highest R2 = 0.54 with the lowest RMSE prediction = 0.031 m3 m−3 given by CMD-MINIEXPLORER. The result demonstrated that the CMD-MINIEXPLORER based measurements better predicted shallow SMC, while deeper SMC was better predicted by GEM-2 measurements. In addition, the ECa measurements obtained through either multi-coil or multi-frequency sensors have the potential to be successfully employed for SMC mapping at the field scale. [ABSTRACT FROM AUTHOR]

Apparent magnetic susceptibility (MSa) as recorded by electromagnetic induction (EMI) instruments could offer relevant information about non-soil subsurface features. It is less affected by natural soil properties than its prominent counterpart, i.e., apparent electrical conductivity (ECa). Hence, MSa is generally a promising approach to investigate artificial inclusions and structures in soil. However, while the origin depth of EMI based ECa is widely accepted, the depth sensitivity (DS) of MSa measurements remains poorly understood. The depth interpretation of MSa is particularly challenging due to negative values especially for objects that are randomly distributed over different depths. Here we assessed the performance of both multi-coil (MC) and multi-frequency (MF) EMI sensors for identifying and determining the DS of MSa measurements in shallow soils through detection of buried small targets of known conductivity. Two experiments were conducted in a sandy loam podzolic soil in western Newfoundland, Canada. Materials of different conductivities, including metal and plastic targets, were buried at depths between 20 and 80 cm. Three inter-coil separations (32, 71 and 118 cm) of the MC sensor and four factory-calibrated frequencies (18, 38, 49 and 80 kHz) of the MF sensor were tested in both horizontal and vertical coil orientations. The MC sensor clearly detected all four metal targets from three coil separations in both coil orientations while the MF sensor identified more anomalies than targets limiting its information value. Based on the measurements from MC and the theoretical DS function, a criterion was developed and validated to assess the potential depth origin of MSa. We found that negative or less than the background values occur, if the depth of the target is shallower than 0.36 times the coil distance of the employed EMI sensor. According to this criterion, the depth origins of metallic targets were correctly identified under the assumption of low induction numbers, even if values were negative. [ABSTRACT FROM AUTHOR]

Recovery of soil health offers insights into the mechanisms underpinning the stability of remediated ecosystems. Indirect assessment of enzymatic activity potential using substrate induced respiration (SIR), is commonly used to evaluate changes in soil microbial activity profiles, with their links to environmental and management factors. In this study, community level physiological profiling (CLPP) was employed to assess the impact of time on surface coal mine soil remediation. When compared with an adjoining control site, analysis of CLPP parameters offer useful insights and prospective tools for assessing soil health, following mining and remediation activities. [ABSTRACT FROM AUTHOR]

Land-use change in the boreal forest region leads to agriculture to be carried out on acid, shallow and low fertility soils. To correct soil fertility and promote crop productivity, manure and inorganic fertilizers are added, increasing the risk for greenhouse gas emissions (GHGE). To reduce the reliance on synthetic soil amendments while taking advantage of locally relevant industrial by-products, wood ash (WA) and paper sludge (SL) have been proposed as soil amendments for a range of soil types. We posited that amending soils with WA , SL and biochar will improve soil health parameters and fertility of boreal soils. Microbial activity resulting to nitrogen losses and availability were assessed. WA had a stronger ameliorative effect on acid boreal soils compared to SL. Both WA and SL increased soil microbial biomass and basal respiration resulting in higher net mineralization and thus significant increases in CO 2 emissions. Co-application of urea with WA or SL further increased net mineralization compared to when used independently. Conversely, the biochar's effect was short-lived and not significant. Nevertheless, addition of biochar was shown to reduce CO 2 emissions in all cases except in WA amended soils. No significant differences were observed in CH 4 emissions across all treatments. WA and SL may improve soil fertility and quality but could also contribute significantly to GHG emissions in acid boreal soils. Further research is recommended to assess the mitigating effect of various biochar feedstocks on GHG emissions when co-applied with WA and SL. • The effect of wood ash and paper sludge on acid soils was tested in incubation tests. • Both increased the soil microbial biomass, respiration, and net mineralization. • Greenhouse gas emissions were larger for paper sludge amended soils. • Supplementing biochar to wood ash increased soil CO 2 fluxes. • Supplementing biochar to paper sludge or limestone ash reduced soil CO 2 fluxes. [ABSTRACT FROM AUTHOR]

Abstract: With the recognition that landscape position affects potential gradients for water movement, the linkages between soil, geology and the quality of groundwater resources have become evident. This paper provides a historical perspective of the contribution that the use of lysimeters has made to our understanding of the physical, chemical and biological features that govern water and contaminant flows through the soil-geological strata-groundwater continuum, leading to contamination of unconfined aquifers. It indicates how we can take action to mitigate effects of some of the land management practices that increase the threats to groundwater resources. The term ‘lysimeter’ has been applied to a wide variety of structures that allow measurement of changes in the volume of water within or flow of water through a bounded soil column of a variety of depths. Some have contained repacked or undisturbed soil from one or more layers, while others have enclosed the three primary soil horizons (A, B and C) together with fractured bedrock layers. Lysimeters have ranged in the size of the upper boundary from a few tens of cm2 to at least 1ha, and in depth from about 20cm to a few metres. Lysimeters were first used to gain an understanding of the importance of water for plants as well as the components of the soil water balance. The quantification of the drainage component was quickly followed by enquiries into the chemical content of the leachate. Lysimeters have been used to quantify the loss of –N by leaching from the soil into shallow groundwater and elucidate the sources of the nitrogen lost at any one time. With the availability of organic pesticides immediately after World War II and their identification in groundwater, considerable attention has been paid to the mechanisms governing their downwards transport and the important role of preferential flow paths in the soil. More recently concerns for the transport of pathogenic microorganisms to groundwater have further highlighted the importance of preferential flow. Lysimeters have permitted investigation of the mechanisms by which these chemical and biological materials, which can be hazardous to human health, reach our sources of drinking water. They have also provided the means of identifying soil management practices that could be used to reduce the movement contaminants in the leachate from agricultural fields. [Copyright &y& Elsevier]

Under food security concerns and accelerated global warming, northern regions are becoming new agricultural frontiers. While diverse regional, national, and local policies support northern agricultural intensification and expansion through land use conversion, the scope and environmental consequences of northern agriculture are yet to be fully understood. As northern agriculture is poised to increase its role in both the local and global food production, its sustainable growth depends on a comprehensive understanding of opportunities and challenges. To evaluate the current perception of the status of northern agricultural research and the extent to which there is a need for a coordinated approach to its growth, we developed a targeted survey delivered online. Questions are aimed at revealing similarities and discrepancies in the awareness of northern agriculture and obtaining feedback on the need for a global synchronization of research and development. Out of 309 respondents, a curated dataset of 238 respondents was employed for analysis. This included respondents with knowledge and expertise in boreal and/or Arctic agriculture (41%), of temperate and/or alpine agriculture (37%), and other respondents (22%). Most are involved in agricultural (60%) or applied environmental (23.5%) sciences. Results revealed that scientists working in the northern regions are cautiously optimistic about climate change–driven expansion of northern agriculture while also realistic about the need for environmentally sustainable agricultural systems. Respondents with limited exposure to northern agriculture were more pessimistic about its expansion. Surprisingly, there was a limited and inconsistent knowledge of extant networks and research entities focusing on northern agriculture research. Nevertheless, there was a strong consensus that a concerted approach among multiple disciplines and across global regions would benefit northern agriculture and its ongoing growth. The survey's results illuminate for the very first time the need for better coordination and a greater emphasis on northern agriculture under climate change. [ABSTRACT FROM AUTHOR]

Despite the agricultural expansion into Canada's boreal ecoregion, little is known about the phosphorus (P) adsorption capacity in natural and managed Podzols' soil profiles. This information is critical for informing management decisions for P use efficiency and mitigating related environmental risks. Thus, this study aimed to evaluate P adsorption characteristics of podzolic horizons in natural and managed soil using nonlinear Langmuir and Freundlich adsorption models. A batch adsorption experiment was conducted using soils collected from distinct horizons of forested and managed fields in eastern and central Newfoundland, Canada. Nonlinear Langmuir and Freundlich fitted models had r values >.99 regardless of horizons, locations, and management history. The organic LFH, a surface horizon typical for forested Podzols, and a long‐term managed Ap horizon had the highest P retention capacities when compared to either newly converted soils or soils used as tree nursery following conversion from natural forest. A significant linear correlation and multiple regression models (p <.05) were established between P adsorption parameters and selected soil properties. Results suggest that following conversion from forest to agricultural use, long‐term management that includes tillage and lime and fertilizer application creates an Ap horizon with strong adsorption capacity, which could still fix P and serve as a source of P. The newly converted soils and the deeper soil horizons, for both natural and converted lands, do act mainly as P sinks; hence, crops may need larger quantities of P fertilizer increasing fertilizer expenses and also increasing future legacy P. [ABSTRACT FROM AUTHOR]

Electromagnetic induction (EMI) technique is an established method to measure the apparent electrical conductivity (ECa) of soil as a proxy for its physicochemical properties. Multi-frequency (MF) and multi-coil (MC) are the two types of commercially available EMI sensors. Although the working principles are similar, their theoretical and effective depth of investigation and their resolution capacity can vary. Given the recent emphasis on non-invasive mapping of soil properties, the selection of the most appropriate instrument is critical to support robust relationships between ECa and the targeted properties. In this study, we compared the performance of MC and MF sensors by their ability to define relationships between ECa (i.e., MF–ECa and MC–ECa) and shallow soil properties. Field experiments were conducted under wet and dry conditions on a silage-corn field in western Newfoundland, Canada. Relationships between temporally stable properties, such as texture and bulk density, and temporally variable properties, such as soil water content (SWC), cation exchange capacity (CEC) and pore water electrical conductivity (ECw) were investigated. Results revealed significant (p < 0.05) positive correlations of ECa to silt content, SWC and CEC for both sensors under dry conditions, higher correlated for MC–ECa. Under wet conditions, correlation of MF–ECa to temporally variable properties decreased, particularly to SWC, while the correlations to sand and silt increased. We concluded that the MF sensor is more sensitive to changes in SWC which influenced its ability to map temporally variable properties. The performance of the MC sensor was less affected by variable weather conditions, providing overall stronger correlations to both, temporally stable or variable soil properties for the tested Podzol and hence the more suitable sensor toward various precision agricultural practices. [ABSTRACT FROM AUTHOR]

Aquatic organisms, such as microalgae ( Chlorella , Arthrospira (Spirulina), Tetrasselmis , Dunalliela etc.) and duckweed ( Lemna spp., Wolffia spp. etc.) are a potential source for the production of protein-rich biomass and for numerous other high-value compounds (fatty acids, pigments, vitamins etc.). Their cultivation using agro-industrial wastes and wastewater (WaW) is of particular interest in the context of a circular economy, not only for recycling valuable nutrients but also for reducing the requirements for fresh water for the production of biomass. Recovery and recycling of nutrients is an unavoidable long-term approach for securing future food and feed production. Agro-industrial WaW are rich in nutrients and have been widely considered as a potential nutrient source for the cultivation of microalgae/duckweed. However, they commonly contain various hazardous contaminants, which could potentially taint the produced biomass, raising various concerns about the safety of their consumption. Herein, an overview of the most important contaminants, including heavy metals and metalloids, pathogens (bacteria, viruses, parasites etc.), and xenobiotics (hormones, antibiotics, parasiticides etc.) is given. It is concluded that pretreatment and processing of WaW is a requisite step for the removal of several contaminants. Among the various technologies, anaerobic digestion (AD) is widely used in practice and offers a technologically mature approach for WaW treatment. During AD, various organic and biological contaminants are significantly removed. Further removal of contaminants could be achieved by post-treatment and processing of digestates (solid/liquid separation, dilution etc.) to further decrease the concentration of contaminants. Moreover, during cultivation an additional removal may occur through various mechanisms, such as precipitation, degradation, and biotransformation. Since many jurisdictions regulate the presence of various contaminants in feed or food setting strict safety monitoring processes, it would be of particular interest to initiate a multi-disciplinary discussion whether agro-industrial WaW ought to be used to cultivate microalgae/duckweed for feed or food production and identify most feasible options for doing this safely. Based on the current body of knowledge it is estimated that AD and post-treatment of WaW can lower significantly the risks associated with heavy metals and pathogens, but it is yet unclear to what extent this is the case for certain persistent xenobiotics. [ABSTRACT FROM AUTHOR]

Electromagnetic induction (EMI) is an established method for mapping field-scale soil water content (SWC). However, the correlation between the recorded apparent electrical conductivity (ECa) and SWC is affected by several factors that can vary across test sites and with environmental conditions. As agricultural practices affect both, ECa and SWC, it is likely that the mismatch in SWC predictions using ECa can be directly or indirectly attributed to agronomic treatment effects. Hence, EMI based SWC predictions are often limited to sites with one soil amendment and strong ECa – SWC correlations. However, non-invasive SWC mapping is particularly desirable for larger agricultural fields, covering different soil amendments. We hypothesized that different agronomic treatments altered the ECa – SWC correlations and consequently the EMI based SWC prediction accuracy. We further hypothesized that a model established on areas with high positive ECa – SWC correlation could be used to predict SWC for areas with unsuitable ECa – SWC correlations. A field-scale experiment was conducted to investigate the effects of six agronomic treatments (including biochar, BC) on SWC, ECa, and ECa – SWC correlation in a silage corn field. We tested the accuracy of three models to predict the SWC of independent data sets using data from i) all treatments (T all ), ii) plots with lowest and iii) plots with highest ECa – SWC correlations. We found statistically significant treatment effects on both, ECa and SWC, although overlapping data ranges were given. Furthermore, the correlations between ECa and SWC were affected by the treatments. Correlations were found to be lowest on nutrient-rich dairy manure plots (T2) and highest on the control plots (T6), likely due to differences in the ionic strength of pore water. BC mitigated the effect of ionic strength for T2 while it showed no measurable effects on ECa on plots receiving inorganic fertilizers. Most accurate SWC predictions were reached by employing T all data (RMSEP 1.40–3.13% vol.). However, models based on T6 data provided similar accuracies (RMSEP 1.46–3.96% vol.) using only 12.5% of the area. The T2 based model performance failed (RMSEP 3.02–7.21% vol.). Results suggest that ECa – SWC models established on non-manured areas could provide best possible SWC predictions and are recommended as training areas if soil texture and mineralogical composition can be expected to be relatively homogeneous. [ABSTRACT FROM AUTHOR]

We evaluated the significance of CaCO3on survival ofP. fluorescensCHA0-Rif at different temperatures. Suspensions of CHA0-Rif were added to soil mixtures at a rate of 106cells g−1soil. Survival was evaluated in sterile or nonsterile mixtures containing 0, 5, 10, 15, or 25% CaCO3. Mixtures were incubated at 4, 15, or 37°C. Water content was adjusted at field capacity. Each treatment was tested in triplicate. Destructive sampling was carried out to verify persistence of culturable CHA0-Rif at different time intervals. Incubation temperature (T), sterilization (S), and their interactions were significant for the decay rates of CHA0-Rif (p < 0.01). At 15°C, the longest survival was measured in the mixtures with the largest CaCO3content. Incubation at 37°C accelerated die-off and thus obscured any possible effect of CaCO3. The maximum decay rate of 1.81 d−1was measured in the nonsterile mixture incubated at 37°C; whereas the minimum decay rate of 0.01 d−1was calculated for the sterile soil incubated at 4°C. Overall,P. fluorescensCHA0-Rif survival was mostly affected by temperature and competitor microorganisms. However, the presence of CaCO3may also have a possible role by suppression of other microorganisms in favor of CHA0-Rif. [ABSTRACT FROM AUTHOR]

• The impact of complex interactions (nutrient availability, light and NaCl) was studied. • At lowest Dg concentration growth was hindered mainly by low nutrient availability. • At higher Dg concentration biomass had higher protein content. • At higher Dg concentration had better photosynthetic performances. • There are trade-offs between light and nutrient availability and salinity inhibition. Utilization of digestate as a source of nutrients must be understood in the context of their effects on light penetration. These conflicting consequences of digestate utilization were verified by growing the cyanobacterium Arthrospira platensis (Spirulina) in artificial seawater supplemented with 2.5 %, 5%, 10 % or 15 % (v/v) of anaerobically digested effluents (digestate) in a fed-batch mode. Therefore, the study investigates the impact of the complex interactions between nutrient availability, increased salinity, which affects negatively the photosynthetic efficiency of A. platensi s and variable turbidities associated with the variable ranges of digestate additions. At the lowest digestate concentration growth was hindered by low nutrient availability. Biomass production was highest at 5% digestate (≈1300 mg/L dry biomass) but further increases in digestate concentrations lowered biomass accumulation (≈1020−1150 mg/L dry biomass). On the other hand, greater concentrations of digestate and thus more nutrients, led to greater protein content (44–55 % in higher concentrations versus 22−30% in the lowest), while A. platensis cells had enhanced photosynthetic performances. The latter is likely due to the fact that addition of digestate reduced light intensity and therefore reduced the negative effect of salinity on the photosynthetic apparatus. The balance between nutrient and light availability, as associated with variable digestate rates, may be managed towards the production of A. platensis biomass with variable qualitative and quantitative biochemical parameters. [ABSTRACT FROM AUTHOR]