Quantitative evaluation of soil health based on a minimum dataset under various short-term crop rotations on the Canadian prairies.

Maintaining and improving soil health (SH) is essential for the long-term sustainability and productivity of agriculture, notably in the face of climate change. This study addressed the challenge of selecting appropriate soil indicators, scoring methods, and indexing approaches for SH evaluation under no-till crop rotations. This study aimed to develop minimum datasets (MDS) and assess SH in six crop rotations (denoted as conventional, diversified, high-risk and high-reward, market-driven, pulse-oilseed intensified, and soil health-enhanced rotations) at three sites on the Canadian prairies. Fourteen soil indicators in the total dataset (TDS) were examined, encompassing both chemical (0-7.5 cm depth) and physical (5-10 cm depth) properties. Principal component analysis (PCA) identified MDSs from the TDS. Two scoring [linear (L) and non-linear (NL)] and two SH indexing approaches [additive (A) and weighted additive (WA)] were used to calculate the SH index (SHI). One-way ANOVA evaluated the SHI among crop rotations. The PCA revealed variations in the number of indicators in the MDS across sites, with soil organic carbon, bulk density, macroporosity, and plant-available water capacity as the common indicators for MDS across sites. Other indicators such as particulate organic matter carbon, aggregate stability, field capacity, and microporosity were found to be important, depending on the site. The non-linear weighted additive SH indexing (SHI.NLWA) proved to be the most sensitive and effective for differentiating among crop rotations in the short-term across study sites (R2 = 0.89-0.94, P < 0.05). Crop rotations significantly influenced SHI, with the diversified and high-risk and high-reward rotations having the highest SHI at Lethbridge and Scott, respectively. Overall, the diversified rotation at Lethbridge and Swift Current, along with the high-risk and high-reward rotation at Scott, exhibited better soil function than other rotations. Monitoring SHI over time and selecting crop rotations that improve SH can collectively enhance soil functions and agroecosystem productivity.

A comparison of Tier 1, 2, and 3 methods for quantifying nitrous oxide emissions from soils amended with biosolids.

Municipal biosolids are a nitrogen (N)-rich agricultural fertilizer which may emit nitrous oxide (N2O) after rainfall events. Due to sparse empirical data, there is a lack of biosolids-specific N2O emission factors to determine how land-applied biosolids contribute to the national greenhouse gas inventory. This study estimated N2O emissions from biosolids-amended land in Canada using Tier 1, Tier 2 (Canadian), and Tier 3 (Denitrification and Decomposition model [DNDC]) methodologies recommended by the Intergovernmental Panel on Climate Change (IPCC). Field data was from replicated plots at 8 site-years between 2017 and 2019 in the provinces of Quebec, Nova Scotia and Alberta, Canada, representing three distinct ecozones. Municipal biosolids were the major N source for the crop, applied as mesophilic anaerobically digested biosolids, composted biosolids, or alkaline-stabilized biosolids alone or combined with an equal amount of urea-N fertilizer to meet the crop N requirements. Fluxes of N2O were measured during the growing season with manual chambers and compared to N2O emissions estimated using the IPCC methods. In all site-years, the mean emission of N2O in the growing season was greater with digested biosolids than other biosolids sources or urea fertilizer alone. The emissions of N2O in the growing season were similar with composted or alkaline-stabilized biosolids, and no greater than the unfertilized control. The best estimates of N2O emissions, relative to measured values, were with the Tier 3 > adapted Tier 2 with biosolids-specific correction factors > standard Tier 2 = Tier 1 methods of the IPCC, according to the root mean square error statistic. The Tier 3 IPCC method was the best estimator of N2O emissions in the Canadian ecozones evaluated in this study. These results will be used to improve methods for estimating N2O emissions from agricultural soils amended with biosolids and to generate more accurate GHG inventories.

The Challenge of ab Initio Calculations in Small Neon Clusters.

Weakly bound neon dimer, trimer and tetramers are studied at HF and CCSD(T) levels using Dunning, ANO and SIGMA-s basis sets. Their ground-state binding energies are studied along with some structural properties. SIGMA-s basis sets have been developed explicitly for this issue but in a manner that can be readily applied to other atoms for the study of larger weakly bound systems. The difficulties for attaining accurate results on these systems are assessed by the computation of total, atomization and correlation energies, as well as equilibrium distances, with several basis sets of increasing size, ranging from non-augmented to double-augmented versions. Extrapolations are proposed to predict stabilization energies and the results are compared with previously published data.

Fluid mixing by an electromagnetically driven floating rotor.

We analyze the mixing properties of a floating stirrer driven electromagnetically in a thin layer of electrolyte, consisting of two free-floating magnets with opposite polarities connected by a rigid coupling. The magnetic rotor is set in circular motion using Lorentz forces created due to the interaction of the magnetic field of the rotor with dc currents actuated in logic sequence. We identify a coherent structure similar to a tripolar vortex whose central vortex rotates in the same direction of the rotor promoting chaotic mixing of the fluid in the laminar regime (Re=45). Dyed water visualization and particle image velocimetry were performed to characterize experimentally the mixing and flow dynamics at the surface of the electrolyte layer. A quasitwo-dimensional numerical simulation based on the immersed boundary method, which incorporates the fluid-solid interaction and reproduces the experimental observations satisfactorily, was carried out. Optimal mixing conditions are determined through the exponential growth of the material interfaces, which are established mainly by varying the distance separating the magnets of the rotor.

Conversion Predictors of Clinically Isolated Syndrome to Multiple Sclerosis in Mexican Patients: A Prospective Study.

BACKGROUND: Clinically Isolated Syndrome (CIS) is the first clinical episode suggestive of Clinical Definite Multiple Sclerosis (CDMS). There are no reports on possible predictors of conversion to CDMS in Mexican mestizo patients. AIM OF THE STUDY: To investigate immunological markers, clinical and paraclinical findings, and the presence of herpesvirus DNA to predict the transition from CIS to CDMS in Mexican patients. METHODS: A single-center prospective cohort study was conducted with newly diagnosed patients with CIS in Mexico between 2006 and 2010. Clinical information, immunophenotype, serum cytokines, anti-myelin protein immunoglobulins, and herpes viral DNA were determined at the time of diagnosis. RESULTS: 273 patients diagnosed with CIS met the enrolment criteria; after 10 years of follow-up, 46% met the 2010 McDonald criteria for CDMS. Baseline parameters associated with conversion to CDMS were motor symptoms, multifocal syndromes, and alterations of somatosensory evoked potentials. The presence of at least one lesion on magnetic resonance imaging was the main factor associated with an increased risk of conversion to CDMS (RR 15.52, 95% CI 3.96-60.79, p = 0.000). Patients who converted to CDMS showed a significantly lower percentage of circulating regulatory T cells, cytotoxic T cells, and B cells, and the conversion to CDMS was associated with the presence of varicella-zoster virus and herpes simplex virus 1 DNA in cerebrospinal fluid and blood. CONCLUSION: There is scarce evidence in Mexico regarding the demographic and clinical aspects of CIS and CDMS. This study shows several predictors of conversion to CDMS to be considered in Mexican patients with CIS.

Genome-wide association analysis provides insights into the genetic basis of photosynthetic responses to low-temperature stress in spring barley.

Low-temperature stress (LTS) is among the major abiotic stresses affecting the geographical distribution and productivity of the most important crops. Understanding the genetic basis of photosynthetic variation under cold stress is necessary for developing more climate-resilient barley cultivars. To that end, we investigated the ability of chlorophyll fluorescence parameters (FVFM, and FVF0) to respond to changes in the maximum quantum yield of Photosystem II photochemistry as an indicator of photosynthetic energy. A panel of 96 barley spring cultivars from different breeding zones of Canada was evaluated for chlorophyll fluorescence-related traits under cold acclimation and freeze shock stresses at different times. Genome-wide association studies (GWAS) were performed using a mixed linear model (MLM). We identified three major and putative genomic regions harboring 52 significant quantitative trait nucleotides (QTNs) on chromosomes 1H, 3H, and 6H for low-temperature tolerance. Functional annotation indicated several QTNs were either within the known or close to genes that play important roles in the photosynthetic metabolites such as abscisic acid (ABA) signaling, hydrolase activity, protein kinase, and transduction of environmental signal transduction at the posttranslational modification levels. These outcomes revealed that barley plants modified their gene expression profile in response to decreasing temperatures resulting in physiological and biochemical modifications. Cold tolerance could influence a long-term adaption of barley in many parts of the world. Since the degree and frequency of LTS vary considerably among production sites. Hence, these results could shed light on potential approaches for improving barley productivity under low-temperature stress.

Contribution of Proteins to the Latin American Diet: Results of the ELANS Study.

Dietary protein intake is vital to life. Here we sought to characterize dietary sources of protein in eight Latin American countries. Survey data were collected for Estudio Latinoamericano de Nutrición y Salud (ELANS); participants were from Argentina, Brazil, Chile, Colombia, Costa Rica, Ecuador, Peru, and Venezuela (n = 9218, 15-65 years old). The primary aim of this analysis was to quantify per-person daily protein consumption by country and sociodemographic factors. Secondary aims: to quantify proportional intake of proteins by source, amount and processing, and to determine the adequacy of protein/essential amino acid intake. Younger groups (adolescents 15-19 years, adults 20-33 years) had the highest intake of proteins; middle-aged adults (34-49 years) had a lower intake, and older adults (50-65 years) had a strikingly lower intake. Protein consumption was higher in men than women. Animal proteins comprised nearly 70% of total daily protein intake in Argentina and Venezuela, contrasting with <60% in Peru, Chile, and Costa Rica. Brazil and Venezuela showed the highest protein intake within the highest education level. The higher the socioeconomic level, the higher the protein intake, except for Argentina, Chile, and Peru. Proportional intake of animal- and plant-based protein generally reflected the food availability by country. This study presents a pre-pandemic regional baseline and offers a perspective for future studies of changes related to government policies, climate, and dietary practices.

Arbuscular mycorrhizal fungi in oat-pea intercropping.

Arbuscular mycorrhizal fungal diversity can be altered by intercropping plant species, as well as N fertilizer applications. This study examined the effects of oat-pea intercropping and N fertilizer addition on the richness and diversity of mycorrhizal species, as well as identified the most common arbuscular mycorrhizal fungi (AMF) genera recruited for oats and peas in two growing seasons (2019 and 2020). The AMF diversity was higher in an intercropped system compared to their respective monocropping system. Under drier conditions in 2019, arbuscular mycorrhizal richness decreased with N fertilizer addition in sole peas and increased with N fertilizer addition in sole oats, but no significant change in richness was observed in oat-pea intercropping. During the wetter growing season 2020, arbuscular mycorrhizal diversity increased when oat and pea were intercropped, compared to either sole oat or sole pea. Diversispora in sole pea was a significant indicator differentiating the root associated AMF community from sole oat. Claroideoglomus richness increased in peas in 2020, thus this genus could be moisture dependent. Paraglomus richness in oat-pea intercropping was similar to sole oat in 2019, and similar to sole pea in 2020. This can suggest that Paraglomus is an indicator of plant stress under intercropping, as based on the premise that stressed plants release more exudates, and the subsequent mycorrhizal associations favor these plants with higher exudation. Future investigations can further reveal the functions and benefits of these mycorrhizal genera in annual monocrop and intercropping systems.

Customizable Collagen Vitrigel Membranes and Preliminary Results in Corneal Engineering.

Corneal opacities are a leading cause of visual impairment that affect 4.2 million people annually. The current treatment is corneal transplantation, which is limited by tissue donor shortages. Corneal engineering aims to develop membranes that function as scaffolds in corneal cell transplantation. Here, we describe a method for producing transplantable corneal constructs based on a collagen vitrigel (CVM) membrane and corneal endothelial cells (CECs). The CVMs were produced using increasing volumes of collagen type I: 1X (2.8 µL/mm2), 2X, and 3X. The vitrification process was performed at 40% relative humidity (RH) and 40 °C using a matryoshka-like system consisting of a shaking-oven harboring a desiccator with a saturated K2CO3 solution. The CVMs were characterized via SEM microscopy, cell adherence, FTIR, and manipulation in an ex vivo model. A pilot transplantation of the CECs/CVM construct in rabbits was also carried out. The thickness of the CVMs was 3.65-7.2 µm. The transparency was superior to a human cornea (92.6% = 1X; 94% = 2X; 89.21% = 3X). SEM microscopy showed a homogenous surface and laminar organization. The cell concentration seeded over the CVM increased threefold with no significant difference between 1X, 2X, and 3X (p = 0.323). The 2X-CVM was suitable for surgical manipulation in the ex vivo model. Constructs using the CECs/2X-CVM promoted corneal transparency restoration.

Passive transfer of SARS-CoV-2 antibodies with platelet transfusions.

BACKGROUND: Although over 5000 platelet transfusions occur daily in the United States, the presence of SARS-CoV-2 antibodies in platelet units is not commonly evaluated for. The effects of platelet transfusions with SARS-CoV-2 antibodies remain largely unknown. We evaluated single-donor (apheresis) platelet units for SARS-CoV-2 antibodies and determined if platelet transfusions passively transferred antibodies to seronegative recipients. STUDY DESIGN AND METHODS: We conducted a retrospective analysis as part of a quality assurance initiative during February to March 2021 at a tertiary referral academic center in suburban New York. Platelet units and platelet recipients were evaluated for the presence of SARS-CoV-2 antibodies using the DiaSorin LIASON SARS-CoV-2 S1/S2 IgG assay. There were 47 platelet recipients eligible for study inclusion. The primary outcome was the presence of SARS-CoV-2 spike protein IgG antibodies in the recipient's blood after platelet transfusion. RESULTS: Twenty-three patients received platelets with SARS-CoV-2 spike protein IgG antibodies; 13 recipients had detection of SARS-COV-2 antibodies (56.5%), and 10 recipients did not. The median antibody titer in the platelet units given to the group with passive antibodies detected was significantly higher compared to the median antibody titer in the platelet units given to the group without antibodies detected (median [interquartile range]: 306 AU/ml [132, 400] vs. 96.1 AU/ml [30.6, 186], p = .027). CONCLUSIONS: Our study demonstrated a significant rate of passive transfer of SARS-CoV-2 spike protein IgG antibodies through platelet transfusions. Considering the volume of daily platelet transfusions, this is something all clinicians should be aware of.

Genetic diversity and population structure assessment of Western Canadian barley cooperative trials.

Studying the population structure and genetic diversity of historical datasets is a proposed use for association analysis. This is particularly important when the dataset contains traits that are time-consuming or costly to measure. A set of 96 elite barley genotypes, developed from eight breeding programs of the Western Canadian Cooperative Trials were used in the current study. Genetic diversity, allelic variation, and linkage disequilibrium (LD) were investigated using 5063 high-quality SNP markers via the Illumina 9K Barley Infinium iSelect SNP assay. The distribution of SNPs markers across the barley genome ranged from 449 markers on chromosome 1H to 1111 markers on chromosome 5H. The average polymorphism information content (PIC) per locus was 0.275 and ranged from 0.094 to 0.375. Bayesian clustering in STRUCTURE and principal coordinate analysis revealed that the populations are differentiated primarily due to the different breeding program origins and ear-row type into five subpopulations. Analysis of molecular variance based on PhiPT values suggested that high values of genetic diversity were observed within populations and accounted for 90% of the total variance. Subpopulation 5 exhibited the most diversity with the highest values of the diversity indices, which represent the breeding program gene pool of AFC, AAFRD, AU, and BARI. With increasing genetic distance, the LD values, expressed as r2, declined to below the critical r2 = 0.18 after 3.91 cM, and the same pattern was observed on each chromosome. Our results identified an important pattern of genetic diversity among the Canadian barley panel that was proposed to be representative of target breeding programs and may have important implications for association mapping in the future. This highlight, that efforts to identify novel variability underlying this diversity may present practical breeding opportunities to develop new barley genotypes.

Exploring food security/insecurity determinants within Venezuela's complex humanitarian emergency.

Introduction: The complex humanitarian emergency that Venezuela has been going through for several years has deteriorated the quality of life of its citizens, deepened food insecurity in households and has promoted migratory movements of almost six million people to neighboring countries. Objective: To analyze food security in Venezuelan households to identify the determinant factors that might contribute to the design of evidence-based public policies. Materials and methods: A non-probabilistic survey of national scope was used in 2,041 urban and non-urban households. A descriptive statistical test was performed to analyze demographic variables and the three component indicators of the food security index (FSI): food consumption, economic vulnerability and coping strategies. The FSI was built according to the World Food Program (WFP) methodology, and a segmentation analysis was applied using the Chi-squared Automatic Interaction Detection (CHAID) algorithm to specify the influence of some variables as the best predictor at each level. Results: Only 9% of the households presented food security, 69% classified as marginally secure, and 22% presented moderate or severe food insecurity. The food consumption score (FCS) was the variable that best discriminated the level of food security, followed by coping strategies and the percentage of spending on food. Conclusion: Most of the households studied sacrifice their livelihoods to feed themselves and cover the minimum of their nutritional requirements. This needs attention to stop and reverse the deterioration within a framework of respect for the human rights to health and food.

Phytochemical Profile and Antioxidant and Antiproliferative Activity of Sedum dendroideum on Pterygium Fibroblasts.

BACKGROUND: Sedum dendroideum has antioxidant effects that are beneficial for different diseases. We aimed to analyze the antiproliferative activity of S. dendroideum in human pterygium fibroblasts (HPFs). METHODS: HPFs were treated for 24 h with 0-1000 µg/mL of S. dendroideum lyophilized to analyze its effect on cell viability using the CellTiter assay. RNA from HPF treated with 250 µg/mL of S. dendroideum lyophilized was isolated, and the expression of VEGF and CTGF genes was evaluated by qPCR. A dermal fibroblast cell line (HDFa) was used as a healthy control. The total phenolic content, antioxidant activity, and chemical profile of S. dendroideum lyophilized were determined. RESULTS: Viability of HPF decreased after 24 h treatment of S. dendroideum in a dose-dependent manner. The expression of VEGF and CTGF significantly decreased (P < 0.01) in HPF treated with 250 µg/mL of S. dendroideum when compared with untreated HPF. The total phenolic concentration in the S. dendroideum lyophilized was 33.67 mg gallic acid equivalents (GAE)/g. Antioxidant activity was 384.49 mM Trolox equivalents/mL. The main phenolic compounds identified by HPLC analysis were the kaempferol-3-O-glycoside, kaempferol-3-O-rhamnoside, kaempferol-3-O-neohesperidoside-7-O-α-rhamnopyranoside, and kaempferol-3-O-glycoside-7-O-rhamnoside. CONCLUSIONS: S. dendroideum decreases the proliferation of HPF and the expression of VEGF and CTGF. The phenolic compound concentration, antioxidant activity, and phytochemical profile may play a role in these effects.

How could simulated dewatering of slurry mitigate nitrous oxide emissions from fall and spring injections? - A modelling study in a Chernozem soil in Western Canada.

Process-based ecosystem models, such as ecosys, can be useful tools to gain insights and accurately project nitrous oxide (N2O) inventories in national, regional and global scales, and to explore potential emission reduction strategies. Our objectives are to investigate how the ecosys model simulate the effects of fall and spring slurry injections on N2O production and if de-watering slurry could become a potential N2O mitigation strategy for both fall and spring injections. The ecosys model was used to simulate hourly N2O fluxes from 2014 to 2017 in a cropping system with and without slurry (fall and spring additions) in comparison with field measurements in Alberta, Canada. Furthermore, we performed simulations of de-watered fall and spring slurry applications in the same scenarios. Our results showed ecosys adequately simulated soil temperatures and moisture contents at 10 and 20 cm depths [correlation coefficients (r) ≥ 0.929 for temperatures; r ≥ 0.529 for moistures]. The divergences of modelled and measured soil water contents during spring thaws could be attributed to uncertainties in model inputs for soil hydrological parameters as well as uncertainties in field measurements. The model captured reasonably well the dynamics of N2O fluxes from soils receiving fall and spring slurry (r = 0.356). However, the concurrent discrepancies of N2O fluxes between modelled and measured values during the wetter spring thaw of 2017 might be a result of an unsatisfactory simulation of snowmelt infiltration and runoff. Compared to whole slurry, simulated de-watered slurry resulted in considerable reductions in cumulative N2O emissions by 16-36 and 23-29% for fall and spring slurry injections, respectively. The model results indicate that de-watering slurry would potentially be an efficient emission mitigation strategy; however, there is still a paucity of studies addressing the feasibility of dewatering as a practice and further research can focus on this knowledge gap.

In vitro effects of citral on the human myometrium: Potential adjunct therapy to prevent preterm births.

BACKGROUND: Premature infants contribute to infant morbidity and mortality especially in low resource settings. Information on tocolytic and/or anti-inflammatory effects of several plant extracts, such as citral, could help prevent preterm birth cases and reduce the number of preterm infants. The aim of this study was to evaluate the in vitro tocolytic and anti-inflammatory effect of citral on myometrial tissues of the human uterus. METHODS: Myometrial samples from uteri obtained after hysterectomy were used in functional tests to evaluate the inhibitory effect of citral on PGF-2α induced contractions. The intracellular cyclic adenosine monophosphate (cAMP) levels generated in response to citral in human myometrial homogenates were measured by ELISAs. Forskolin was used as a positive control. The anti-inflammatory effect of citral was determined through the measurement of two pro-inflammatory cytokines, tumor necrosis factor-α (TNFα) and interleukin (IL)-1ß, and the anti-inflammatory cytokine IL-10, in human myometrial explants stimulated with lipopolysaccharide (LPS). RESULTS: Citral was able to induce a significant inhibition of PGF-2α induced contractions at the highest concentration level (p < .05). Citral caused a concentration-dependent increase in myometrial cAMP levels (p < .05) and a concentration-dependent decrease in LPS-induced TNFα and IL-1ß production, while IL-10 production increased significantly (p < .05). The anti-inflammatory and tocolytic effects induced by citral could be associated with an increase in cAMP levels in human myometrial samples. CONCLUSION: These properties place citral as a potentially safe and effective adjuvant agent in preterm birth cases, an obstetric and gynecological problem that requires urgent attention.

Post-COVID-19 Cholangiopathy: A Novel Entity.

INTRODUCTION: Liver chemistry abnormalities are a frequent manifestation of coronavirus disease 2019 (COVID-19) but are usually transient and resolve with disease resolution. METHODS: We describe the clinical course and histologic features of 3 adults who developed prolonged and severe cholestasis during recovery from critical cardiopulmonary COVID-19. RESULTS: These patients had clinical and histologic features similar to secondary sclerosing cholangitis of the critically ill patient, but with unique histologic features including severe cholangiocyte injury and intrahepatic microangiopathy suggestive of direct hepatic injury from COVID-19. DISCUSSION: We believe that these cases constitute a novel severe post-COVID-19 cholangiopathy with potential for long-term hepatic morbidity.

How does management legacy, nitrogen addition, and nitrification inhibition affect soil organic matter priming and nitrous oxide production?

Long-term management of croplands influences the fluxes and sources of nitrous oxide (N2 O). We examined this premise in a greenhouse study by using soils collected from a 38-yr-old field experiment. The sampled treatments were continuous barley (Hordeum vulgare L.; CB), continuous fescue (Festuca rubra L., F. arundinacea Schreb; CF), and two phases of an 8-yr rotation: faba bean (Vicia faba L.; FB) and alfalfa (Medicago sativa L.)-bromegrass (Bromus inermis Leyss) hay. Barley was grown as a test crop in the greenhouse in each soil. The ranking of N2 O emissions was hay > FB > CB > CF (P < .001). We quantified the 15 N-site preference to assess the N2 O-producing processes. Denitrification was the predominant source, contributing 77.4% of the N2 O production. We also evaluated nitrogen (N) additions: urea alone or urea with a nitrification inhibitor (nitrapyrin or DMPSA). Compared with urea alone, nitrapyrin and DMPSA reduced N2 O emissions by 16 and 25%, respectively. We used urea labeled with 15 N to trace N to N2 O emissions, aboveground plant N uptake, and N retention by soils. Total 15 N-recovery (N2 O + plant + soil) was highest under FB (86%) and lowest under CB (29%). We further separated the N2 O derived from urea versus N2 O from soil organic matter (SOM). The inhibitor DMPSA reduced the N2 O derived specifically from added urea-N by more than half (P < .001). With the addition of urea, N2 O production from mineralization of SOM-N accelerated over the control (without urea), termed the priming effect. This priming of SOM-N contributed with 13% of the total N2 O production when averaged across the four management legacies. The CB soil had the highest proportion of priming-derived N2 O (24%). Management legacies clearly differed in soil carbon and N, which governed N2 O production from denitrification and SOM priming.

Sources and priming of nitrous oxide production across a range of moisture contents in a soil with high organic matter.

Adding nitrogen fertilizers to agricultural soils contributes to increasing concentrations of nitrous oxide (N2 O) in the atmosphere. However, the impacts of N addition on soil organic matter (SOM) turnover, SOM availability, and the ensuing SOM-derived N2 O emissions remain elusive. Within this context, the net change in direction and rate of SOM-derived N2 O production triggered by added N is termed the N2 O priming effect. This incubation study examined the sources and priming of N2 O production as a function of urea addition and multiple moisture contents in a soil with high SOM (55 g organic C kg-1 ). We assessed four water-filled pore space (WFPS) conditions: 28, 40, 52, and 64%. Relative to controls receiving no N, urea addition increased N2 O production by 2.6 times (P < .001). Cumulative N2 O production correlated well with nitrification rates (r = .75; P = .03). We used 15 N-labeled urea to trace the added urea into N2 O. Of the N added via urea, the recovery as N2 O-N shifted from 0.02 to 0.17% when WFPS increased from 28 to 64% (P < .05). We also partitioned the N2 O production into urea vs. SOM sources. More N2 O was sourced from SOM than urea, with 59 ± 2% N2 O originating from SOM. The magnitude of SOM-derived N2 O under urea was larger than that of the control, revealing that positive N2 O priming was triggered by urea addition. Upon subtracting the controls, the primed N2 O was a consistent 19 ± 2% of the total N2 O produced by urea-amended soils. Nevertheless, the priming magnitude rose sharply with increasing moisture by more than one order of magnitude from 4 to 48 µg N2 O-N kg-1 soil and in exponential mode (R2   = .98). Soil moisture, SOM, and nitrification interacted to drive the sources and priming of N2 O.

Can fertigation reduce nitrous oxide emissions from wheat and canola fields?

Increasing nitrogen fertilization and irrigation can contribute to nitrous oxide (N2O) emissions from agriculture. Relative to the conventional practice of one-pass fertilization with all N applied at crop seeding, this study examined how splitting the total N fertilization into seeding time and in-crop fertigation impacts N2O emission factors (EF) in irrigated wheat (Triticum aestivum) and canola (Brassica napus) in Southern Alberta, Canada during two growing seasons (May to Oct. in 2015 and 2016). With all the N applied at crop seeding, the growing-season N2O EF of irrigated wheat and canola was in average 0.23 ± 0.03%. Conversely, implementing N fertigation lowered the magnitudes of N2O EF in each of the four crop-years, averaging 0.16 ± 0.04%. Most of the reductions in N2O emissions due to fertigation occurred with low and intermediate N rates (total rates of 60 and 90 kg N ha-1) and in the second year of the study. This second year had recurrent, early-season rainfalls following seeding (and prior to fertigation) that triggered differences in the daily and cumulative N2O fluxes. Within this year, fertigation on wheat consistently lowered the growing-season N2O EF from a high of 0.27% to only 0.11% (P < 0.001). Also, at the intermediate rate of 90 kg N ha-1, fertigation synergistically reduced the N2O EF of canola by half, from 0.13% to 0.06% (P < 0.01). However, the mitigating effects of fertigation vanished with the highest N rate in the study (120 kg N ha-1). Even with fertigation, this highest N rate resulted in high emissions in wheat, and lesser so in canola in part due to the higher N uptake of canola. Moreover, canola often manifested narrower ratios of N2O emission-to-grain yield (EFyield) than wheat. This interplay of crop species, rainfall and N management suggests that implementing fertigation with reduced N rates can proactively mitigates N2O.