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In southern Manitoba, Canada, a survey was carried out in 2012 and 2013 to determine the presence of Heteroderidae cyst-forming plant-parasitic nematodes, with a focus on the soybean cyst nematode (SCN) (Heterodera glycines). A total of 48 fields having grown soybean were sampled. A modified Fenwick elutriation-flotation technique was used to extract cysts with a 75% cyst recovery efficiency. Cyst population density averaged 0.9 cysts kg−1 soil, with a total of 65 cysts recovered. Preliminary screening of cysts, based on general body shape and vulval cone top structure, showed the presence of cysts belong to circumfenestrate, and ambifenestrate groups of cyst-forming nematodes. Limited morphological data was accessible due to poor quality or insufficient cysts for analysis; however, generated DNA sequences for nuclear rDNA ITS and D2-D3 expansion region of the 28S rRNA were obtained for four samples and matched sequences in GenBank for the cyst nematodes Cactodera milleri, C. torreyanae, C. weissi, C. estonica and unknown Cactodera species. Only one of the ambifenestrate cysts with a cone top structure of Heterodera species yielded DNA for analysis and its identification was ambiguous for soybean cyst nematode (SCN). None of the cysts were positive through SCN diagnostic PCR. Cactodera is not a pest of soybean or other crops in Manitoba. These cyst nematodes are likely to be naturally associated with weeds and grasses in the sampled fields or may be introduced from neighbouring states of the USA. Further annual surveys are needed and recommended in the near future to encompass more soybean fields and corroborate the absence of the pest. [ABSTRACT FROM AUTHOR]

Strip‐tillage is an emerging conservation tillage/residue management system for corn production in the Northern Great Plains. Producers in Manitoba are becoming more interested in strip‐tillage as it may provide many of the soil conservation benefits of no‐tillage production without potential limitations of cold soils in the spring common to this region. A 2‐year study evaluated corn (Zea mays L.) response to phosphorus (P) fertilization in strip‐tillage and conventional tillage systems. Fertilization treatments included a control (no P), two rates of P (30 and 60 kg P2O5 ha−1), applied as monoammonium phosphate (11–52–0) either in the fall with a strip‐tillage unit (as a deep‐band, 10–13 cm deep) or in the spring with a corn planter (as a side‐band, 5 cm beside and 2.5 cm below the seed). Spring side‐banded P treatments increased early‐season biomass at 2 of 4 site‐years by up to 103% compared to the unfertilized controls. At the same 2 site‐years, banded P treatments reduced days to silking by 2–3 days, compared to the unfertilized controls. Across all site‐years, spring side‐banded P treatments increased grain yield by an average of 467 kg ha−1 and decreased grain moisture content by 9 g kg−1 compared to the unfertilized control. Overall, side‐banded P at planting was agronomically superior to precision fall deep‐banding. There was also no agronomic penalty for corn grown with strip‐tillage, compared to conventional tillage, suggesting that strip‐tillage is an agronomically promising practice for corn production in southern Manitoba. Core Ideas: Corn growth, grain yield, and grain moisture responses to strip‐tillage and conventional tillage were similar.Spring side‐banded P fertilizer increased or advanced corn growth, increased grain yield, and reduced grain moisture.Corn growth and yield response to fall deep‐banded P fertilizer was not as consistent as for spring side‐banded P.Corn response to P fertilization generally declined as the growing season progressed.Strip‐tillage shows potential for maintaining corn productivity and protecting soil from erosion in this region. [ABSTRACT FROM AUTHOR]

The development of beneficial management practices is a key strategy to reduce greenhouse gas (GHG) emissions from animal agriculture. The objective of the present study was to evaluate the impact of time and amount of hog manure application on farm productivity and GHG emissions from a cow-calf production system using two whole-farm models. Detailed model inputs (climate, soil and manure properties, farm operation data) were collected from a 3-year field study that evaluated the following three treatments: no application of hog manure on grassland (baseline); a single application of hog manure on grassland in spring (single); and two applications of hog manure as fall and spring (split). All three treatments were simulated in a representative cow-calf production system at the farm-gate using the following whole-farm models: a Coupled Components Model (CCM) that used existing farm component models and the Integrated Farm System Model (IFSM). Annual GHG intensities for the baseline scenario were 17.7 kg CO2-eq/kg liveweight for CCM and 18.1 kg CO2-eq/kg liveweight for IFSM. Of the total farm GHG emissions, 73-77% were from enteric methane production. The application of hog manure on grassland showed a mean emission increase of 7.8 and 8.4 kg CO2-eq/kg liveweight above the baseline for the single and split scenarios, respectively. For the manured scenarios, farm GHG emissions were mainly from enteric methane (47-54%) and soil nitrous oxide (33-41%). Emission estimates from the different GHG sources in the farm varied between models for the single and split application scenarios. Although farm productivity was 3-4% higher in the split than in single application (0.14 t liveweight/ha), the environmental advantage of applying manure in a single or split application was not consistent between models for farm emission intensity. Further component and whole-farm assessments are required to fully understand the impact of timing and the amount of livestock manure application on GHG emissions from beef production systems.

Soil N2O emissions vary with N source. A study was undertaken on a clay soil in the Red River Valley, Manitoba, Canada, to determine the effect of granular N fertilizers and dairy manure on N2O emissions from a field cropped to rapeseed (Brassica napus L.) in 2009 and spring wheat (Triticum aestivum L.) in 2010. Treatments included an unamended control, granular urea, controlled-release urea (ESN), stabilized urea (SuperU), and solid dairy manure added at rates to achieve a total of 140 kg available N ha–1 (product plus soil N test). The N fertilizers were broadcast and shallowly incorporated each spring before planting; the manure was broadcast incorporated the previous fall. Nitrous oxide emissions were monitored from planting to freeze in fall and during spring thaw in 2011 using static-vented chambers. In both years, N2O emissions occurred within 4 to 5 wk of planting but not in fall after manure application. Area-scale cumulative N2O emissions (ΣN2O, kg N ha–1) from planting to freeze were control < ESN = manure < urea = SuperU. Nitrous oxide emission factors were 0.017 kg N2O-N kg–1 available N added for urea and SuperU and 0.007 kg N2O-N kg–1 available N for ESN. Seventy-eight percent of the variation in ΣN2O could be explained by NO3– intensity, an integration of soil NO3– concentrations during the study periods. Greater ΣN2O were also associated with higher yields. These findings suggest that N release rates, as indicated by NO3– intensity and yield, determined N2O emissions. The results highlight the challenge of meeting crop demand yet reducing N2O emissions by selection of an N source.

A 2-year crop rotation study in southern Manitoba assessed the effects of starter fertilizer on grain corn (Zea mays L.) production when corn followed canola (Brassica napus L.) versus soybean (Glycine max L. Merr.). Treatments included a control (no starter) and two rates of phosphorus (P) (30 and 60 kg P2O5 ha−1) as monoammonium phosphate (MAP, 11–52–0) or MicroEssentials® SZ (MESZn, 12–40–0–10–1) side-banded at planting. The preceding crop did not have any influence on mycorrhizal colonization of corn roots at the V4 corn growth stage. However, side-banded fertilizer increased early-season biomass by as much as 111% compared to the unfertilized control, averaged across all site-years, with the largest increases occurring where corn followed canola. P concentration and uptake in early-season biomass increased as the P rate increased. Zinc (Zn) concentrations in early-season biomass were the greatest for the unfertilized control and MESZn treatments, while Zn uptake was significantly greater with the application of starter fertilizer compared to the unfertilized control. Starter P advanced silking date by 2–7 days relative to the unfertilized control. At maturity, starter P reduced grain moisture by 21–27 g kg−1 in corn only after canola. The high rate of MAP increased grain yield by an average of 770 kg ha−1 compared to the unfertilized control, regardless of the preceding crop. The negative influence of the preceding canola crop on early-season growth and mid-season development of corn can be managed with starter fertilization to provide adequate P and Zn to the corn crop and maintain successful production in Manitoba. [ABSTRACT FROM AUTHOR]

Opportunities exist to reduce nitrous oxide (N2O) emissions from nitrogen (N) fertilizers using enhanced efficiency fertilizers (EEFs) and managing application timing. This study examined (1) application timing (fall/spring) and (2) fertilizer N source on N2O emissions, yield, and N uptake of Canadian hard red spring wheat (Triticum aestivum L.) in Southern Manitoba. Fertilizer N sources included granular urea and four EEF products: (1) polymer‐coated urea (environmentally smart nitrogen [ESN]); (2) urea plus nitrification inhibitor (eNtrench); (3) urea plus urease inhibitor (Limus); and (4) urea plus nitrification and urease inhibitor (SuperU). Nitrification‐inhibited products most consistently reduced N2O emissions while maintaining productivity. Compared to urea alone, urea + eNtrench was most effective in reducing cumulative N2O emissions by 47%–64% at four of six site‐years. SuperU reduced N2O emissions by 37%–57% at three of six site‐years. ESN and urea + Limus did not affect emissions in most years. Wheat yield, protein, and N uptake were unaffected by N source in five of six site‐years. Compared to spring, fall application gave greater N2O emissions by 33%–67% at three of six site‐years due to spring‐thaw emissions. Fall was inferior to spring application in wetter site years with lower yield, protein, and N uptake. Overall, nitrification‐inhibited products—either alone or with a urease inhibitor—are a promising tool to reduce N2O emissions while maintaining wheat productivity in Manitoba. However, given that there were few consistent increases in yield or protein, the additional cost of the inhibitors will be a barrier to adoption. Core Ideas: EEF products with nitrification and nitrification/urease inhibitors consistently reduced N2O emissions.Controlled release urea and urease‐inhibited urea did not reduce N2O emissions.Fall application of urea increased N2O emissions in three site‐years compared to spring application.The nitrification inhibitors applied with urea in fall or spring were effective to reduce N2O emissions.Overall, fall application decreased yield, grain protein, and N uptake in relatively wet years. [ABSTRACT FROM AUTHOR]

This study examined fertilizer nitrous oxide (N2O) emissions and canola (Brassica napus L.) grain yield for two granular urea sources (conventional and a dual urease and nitrification inhibitor [SuperU]) and three at‐planting placement methods (broadcast‐incorporated, shallow banded, and deep banded) on commercial fields in Manitoba. Nitrogen (N) rates were 100% and 70% of what was recommended based on soil test and target yield, with the 100% treatments having N2O emissions monitored. SuperU fertilizer consistently reduced N2O emissions (area‐, N‐applied‐, and yield‐based) compared to urea. Significant reductions in N2O emissions with SuperU occurred in four of six site‐years and coincided with delayed nitrification. Compared to broadcast‐incorporated, subsurface banding of conventional urea reduced N2O emissions in drier site‐years but increased emissions when rainfall was higher (especially in shallow banded urea). Across all six site‐years, shallow banding of urea resulted in significantly higher emission intensities than all other treatments. Nitrogen placement did not affect the emission reduction benefit of SuperU. N source or placement did not greatly affect canola yield within either 100% or 70% N rates. Fertilizer N recovery efficiency was also not greatly impacted by either N source or placement. The results demonstrate that dual inhibited granular urea fairly consistently reduces N2O emissions in canola production in southern Manitoba, whereas nitrogen placement had variable effects depending on growing season rainfall. However, with little agronomic benefit, the added cost of enhanced efficiency fertilizers must be overcome for widespread adoption and to achieve greenhouse gas reduction targets for the Canadian agriculture sector. Core Ideas: N2O emissions could have been reduced using a more realistic yield goal and thus lower N rates.SuperU fertilizer reduced N2O emissions compared to urea.Subsurface banding of urea reduced emissions in drier years but increased them in wetter years.Shallow subsurface banding urea tended to increase emissions.SuperU mitigated emissions with shallow banding. [ABSTRACT FROM AUTHOR]

Drip irrigation is a useful practice to enhance water and fertilizer nitrogen (N) use efficiency. However, the use of drip irrigation to mitigate nitrous oxide (N2O) emissions in agricultural systems globally is uncertain. Here, we performed a global meta‐analysis of 485 field measurements of N2O emissions from 74 peer‐reviewed publications prior to March 2021, to quantify the fertilizer‐induced N2O emission factor (EF) of drip irrigation and examine the influencing factors of climate, crop, soil properties, and source and rate of fertilizer N application. The results showed that drip irrigation reduced (p < 0.05) N2O emissions by 32% and 46% compared to furrow and sprinkler irrigation systems, respectively. The overall average EF with drip irrigation was 0.35%, being two‐thirds lower than the IPCC Tier I default value of 1% (kg N2O‐N/kg added fertilizer N). The EF was not significantly affected by climate, crop, soil texture, soil organic carbon content, and pH. The EF was also not significantly (p > 0.05) affected by synthetic N fertilizer source despite a lower numerical value with enhanced efficiency than conventional fertilizers. The EF increased significantly (p < 0.001) with N addition rate in a binomial distribution. Using the IPCC default EF overestimated N2O emissions inventories for drip‐irrigated cropping systems by 7614 and 13,091 Mg per year for China and the globe, respectively. These results indicate that drip irrigation should be recommended as an essential N2O mitigation strategy for irrigated crop production. [ABSTRACT FROM AUTHOR]

A study of the influence of freezing on soil microbial C and N as measured by CHCl3 fumigation-extraction (CFE) reveals that freezing significantly affects the microbial elements after seven days of continuous freezing. Nonfrozen soil was used in the study since the soils frozen before the CFE yield inaccurate results about the influence of freezing. The study is performed by freezing the soil and also by subjecting the soil to freeze throw cycles. During CFE, the physical disruption of soil is very high and hence interference of a aggregate stability is large, making it incapable of removing any interference of aggregate stability.

Improving N fertilization in croplands could minimize soil emissions of nitrous oxide (N2O) and mitigate climate change. This study investigated the effects of spring vs. fall N applications of conventional vs. enhanced‐efficiency N fertilizers (EENFs) on N2O emissions and N use efficiency in spring wheat (Triticum aestivum L.) over 2.5 yr in Alberta, Canada. Fertilizers were anhydrous ammonia and urea and the EENF formulations included urease and nitrification inhibitors and a polymer coating. We measured a fertilizer N2O emission factor of 0.31 ± 0.04%. Irrespective of N fertilizer and timing options peak N2O emissions were evident following soil thawing and major rainfalls. Because most of the annual N2O emissions were associated with soil thawing, spring‐applied N emitted half the N2O of the fall‐applied N during the second study year (P <.001). Conversely, the opposite was observed for the first study year when overall N2O emissions were 36% larger for spring‐ than fall‐applied N (P =.031) as major rainfalls occurred shortly after the spring N fertilization. Nevertheless, within this first study year, EENFs significantly reduced N2O emissions (by 26% on average; P =.019), with a tendency for 11% higher grain yield across springtime EENFs than for conventional fertilizers. Concomitantly, spring‐applied N doubled the fertilizer N recovery efficiency in the same year (P =.023). The soil at the study site inherently had high N availability (NH4 and NO3) and this probably moderated the beneficial effects of EENFs on N2O emissions and grain yields. Results suggest that spring EENFs can mitigate the risk for N2O emissions while sustaining high yields even under scenarios with high availability of native soil N. [ABSTRACT FROM AUTHOR]

Application of inorganic nitrogen (N) fertilizer and manure can increase nitrous oxide (N2O) emissions. We tested the hypothesis that increased N2O flux from soils amended with manure reflects a change in bacterial community structure and, specifically, an increase in the number of denitrifiers. To test this hypothesis, a field experiment was conducted in a drip-irrigated cotton field in an arid region of northwestern China. Treatments included plots that were not amended (Control), and plots amended with urea (Urea), animal manure (Manure) and a 50/50 mix of urea and manure (U+M). Manure was broadcast-incorporated into the soil before seeding while urea was split-applied with drip irrigation (fertigation) over the growing season. The addition treatments did not, as assessed by nextgen sequencing of PCR-amplicons generated from rRNA genes in soil, affect the alpha diversity of bacterial communities but did change the beta diversity. Compared to the Control, the addition of manure (U+M and Manure) significantly increased the abundance of genes associated with nitrate reduction (narG) and denitrfication (nirK and nosZ). Manure addition (U+M and Manure) did not affect the nitrifying enzyme activity (NEA) of soil but resulted in 39–59 times greater denitrifying enzyme activity (DEA). In contrast, urea application had no impact on the abundances of nitrifier and denitrifier genes, DEA and NEA; likely due to a limitation of C availability. DEA was highly correlated (r = 0.70–0.84, P < 0.01) with the abundance of genes narG, nirK and nosZ. An increase in the abundance of these functional genes was further correlated with soil NO3−, dissolved organic carbon, total C, and total N concentrations, and soil C:N ratio. These results demonstrated a positive relationship between the abundances of denitrifying functional genes (narG, nirK and nosZ) and denitrification potential, suggesting that manure application increased N2O emission by increasing denitrification and the population of bacteria that mediated that process. [ABSTRACT FROM AUTHOR]

A soil column experiment was conducted to examine the effects of fertilizer N source and depth of placement on soil profile N2O accumulation and surface emissions at 44% and 77% water-filled pore space (WFPS). The used N fertilizers were polymer-coated urea, stabilized urea with urease and nitrification inhibitors, and conventional granular urea. Conventional urea and stabilized urea were applied either uniformly at 0-65 cm or deeply at a 40- to 65-cm depth of 65 cm repacked soil columns, whereas polymer-coated urea was subsurface banded at a 10-cm depth to reflect fertilizer application practices at a field scale. Profile N2O concentrations at 5, 15, 30, and 60 cm and surface flux were monitored over 3 months. Compared to conventional urea, stabilized urea and polymer-coated urea generally reduced N2O accumulation in the column, but not cumulative emissions. Across fertilizer sources, compared with uniform addition, deep placement reduced column N2O accumulation at 44% but not at 77% WFPS. Deep placement also reduced emissions 56-71% than for uniform placement. Column N2O accumulation doubled at 77% than 44% WFPS, whereas cumulative emissions and applied N-based emission factors were lower at the former WFPS value. Cumulative N2O emissions increased exponentially with total accumulation at 44% but not 77% WFPS. Reduced N2O emissions at high WFPS were likely due to consumption and low diffusivity of the gas in the soil profile, rather than low production by denitrification. These results suggest fertilizer N leached down the profile is less prone to N2O loss while emission reductions by using more efficient fertilizers may be limited. [ABSTRACT FROM AUTHOR]

Optimizing nitrogen (N) fertilizer management in irrigated potato (Solanum tuberosum L.) on coarse-textured soils is challenging. The “4R” nutrient stewardship framework of using N fertilizer at the right rate, right source, right placement and right time provides approaches to improve fertilizer use efficiency while maintaining or improving yield. This 3-years replicated field plot study evaluated effects from a series of N fertilization strategies including 10 combinations of sources, placement and timing, as well as fertigation, on irrigated processing potato (cv. Russet Burbank) grown for a total of five site-years in the Province of Manitoba, Canada. Treatments were designed to provide early to late availability of N to the potato crop. Nitrogen was applied to 80% of Provincial N recommendation to increase the likelihood of observing improved fertilizer use efficiency and effects of treatments on yields. Measurements were tuber yield, size distribution, specific gravity, hollow-heart rate, fertilizer apparent N recovery (ANR) and agronomic nitrogen use efficiency (NUE). Results showed differences in yield, quality, ANR and NUE between fertilizer treatments were generally very small or absent. Average tuber marketable yields for fertilizer treatments were significantly greater than those for the unfertilized control (P < 0.001). Split application of urea at planting and hilling, and urea at planting with fertigation occasionally increased tuber marketable yields on sites of coarse textured soils (P < 0.05). Use of polymer-coated urea (ESN) or stabilized urea with inhibitors (SuperU) did not affect yield, quality or N use of potato. Site-year difference (P < 0.001) were apparent for all measures highlighting the importance of soil and climatic conditions on agronomic and environmental effects of N management practices. The results indicate current grower practice of split urea application at planting and hilling and urea at planting following by in-season fertigation are sound. Results indicate growers could shift to the more convenient practice of ESN at planting without reducing yields. Absence of treatment effects suggests N was generally not a limiting factor for the current study, indicating that the current recommendation for potato production in Manitoba over-estimate site-specific crop N needs. [ABSTRACT FROM AUTHOR]

Conversion of native desert into irrigated cropland is common in southern Taklimakan desert of China though the effect on soil fertility are not well understood. This study examined the effect of cultivation intensity on soil properties and crop productivity using 9-year data from cotton grown at three intensities of no fertilizer, low, and high fertilizer inputs. A native desert with sparse vegetation of Alhagi sparsifolia Shap. was used as a check. Treatment effects on soil properties fluctuated during 2005-2009 due to mineralization of applied manure or weather variation, and kept stable during 2010-2013. Soil organic carbon (SOC) during 2010-2013 increased with intensity, being 1.0-2.4 times greater in the fertilized than unfertilized cotton and desert. Soil total N, plant available N, and P content increased with fertilizer inputs. Available N content in the desert was 28.8 mg kg−1, being comparable to the low fertilizer treatment but approximately double that of unfertilized cotton, suggesting N fixing capacity of the leguminosae A. sparsifolia. Available K content was highest in desert and decreased with cultivation intensity. There were positive relationships between SOC and available N and P contents, suggesting SOC as a nutrient reservoir. Soil C:N ratio during 2010-2013 increased with intensity, being 8.7, 9.7, 10.8, and 12.0, for desert, no fertilizer, low, and high fertilizer input, respectively. Fertilizer application increased the 2010-2013 average cotton seed yield by 4.3-6.4 times compared to the unfertilized cotton field. In conclusion, our results suggest the intensive inputs of fertilizers are crucial to accelerate soil fertility and maintain the productivity of the recently converted lands from the desert. [ABSTRACT FROM AUTHOR]

Ditylenchus weischeri that parasitizes the weed Cirsium arvense (L.) Scop., 1772, (creeping thistle) was described in 2011 from Russia based on their morphology, ITS-RFLP analysis, and Hsp90 gene sequence of a few individuals and one field collection of the plant. More recently, we found C. arvense parasitized by D. weischeri in the Prairie Provinces of Canada. Plant host preference for D. weischeri was also distinct from D. dipsaci (Kühn) Filipjev, 1936. In the current study, a comprehensive molecular analysis of many D. weischeri specimens from Canada is presented. Individuals from 41C. arvense or yellow pea grain samples with seeds of C. arvense from the Prairie Provinces were sequenced for the internal transcribed spacer (ITS rDNA), large subunit (LSU) D2D3 28S rDNA, partial segment of small subunit (SSU) 18S rDNA, and the heat shock protein Hsp90 gene. The analysis also included D. weischeri individuals from C. arvense from Russia and garlic with D. dipsaci from the Provinces of Ontario and Quebec in Canada. Available sequence data of Ditylenchus species retrieved from GenBank were used to phylogenetically position this species within the genus Ditylenchus. In all studied genes, several single-nucleotide polymorphisms between the Canadian D. weischeri and both Russian haplotype and individuals of D. weischeri from C. arvense from Russia were found. The sequences of ITS rDNA, LSU D2D3 28S rDNA, and Hsp90 were used to construct separate dendrograms. For each of the three genes examined, D. weischeri was grouped separately from the other Ditylenchus. Ditylenchus samples from C. arvense was positioned to a single clade such as D. weischeri and distinct from D. dipsaci. With past reports of plant host preference and morphology, the results of this study provide further evidence for the fact that D. weischeri is distinct to be separated from D. dipsaci. Furthermore, minor differences in molecular divergence and morphology to the Russian haplotype and limited symptoms of disease on C. arvense in Prairie Canada suggest the Canadian and Russian populations of D. weischeri may be diverging. [ABSTRACT FROM AUTHOR]

Agriculture is the major anthropogenic contributor to global nitrous oxide (N 2 O) emissions. Many studies have examined soil N 2 O emissions from synthetic nitrogen (N) fertilizer additions, however, in organic production where plough-down of forage legumes are often used as a nitrogen source, emissions are as not well understood. In the current study, the Glenlea Long-Term Organic Crop Rotation Study near Winnipeg, Manitoba, was used to compare N 2 O emissions of a conventional annual grain and an organic mixed forage-grain system. Static-vented chambers were used to determine N 2 O emissions for the 2014 and 2015 crop years; from spring planting to freeze-up and again during thaw following spring. plots monitored were spring wheat and two-cut harvest with late-summer or early-fall plough-down alfalfa for the organic system, and spring wheat and soybean for the conventional system were monitored in each study year. The organically produced alfalfa received composted dairy manure in 2014 and only conventional wheat crops received fertilizer N as urea. Cumulative emissions (g N 2 O-N ha −1 ) with organic wheat were half that of conventional management. Cumulative emissions for the legume crops in the 2014 crop year were very low (<200 g N ha −1 ) and not affected by management. No or very low emissions occurred shortly after plough-downs in 2014 and 2015, and during thaw in 2015. However, fall soil moisture was higher in 2015 resulting in nitrate accumulation from alfalfa plough-down and high subsequent N 2 O emissions during spring thaw in 2016. Over both study years, management did not affect yield-scaled emissions for wheat unless thaw emissions from ploughed down alfalfa were included. In conclusion, the benefit of organic cropping on N 2 O emissions was dependent upon the soil moisture level in fall that preceded the spring thaw period. [ABSTRACT FROM AUTHOR]

Ditylenchus weischeri was recently reported in the provinces of Manitoba and Saskatchewan, Canada. Populations of D. weischeri from creeping thistle (Cirsium arvense L.) in Manitoba and D. dipsaci from garlic (Allium cepa L.) in Ontario were examined for their potential to grow on callused carrot (Daucus carota subsp. sativus) disks, alfalfa (Medicago sativa L.) and creeping thistle callus tissues, and pure cultures of eight fungal species, Botrytis cinerea, Fusarium solani, Rhizoctonia solani, Verticillium dahliae, Sclerotinia sclerotiorum, Cladosporium cucumerinum, Colletotrichum gloeosporioides, and Chaetomium spp. Ditylenchus weischeri and D. dipsaci could not be reared on any of the fungal isolates nor in the callus tissues of creeping thistle. In contrast to D. weischeri, D. dipsaci was successfully reared on the alfalfa callus tissue. On the callused carrot disks, with no media, an increase of 54 and 244 times the initial density of 80 nematodes was obtained for D. weischeri and D. dipsaci, respectively. Monoxenic rearing was performed using callused carrot disks to provide sufficient D. weischeri inoculum for the microplot study. The effect of D. weischeri on yellow pea varieties Agassiz and Bronco was determined in a microplot trial using initial densities of 0, 100, 200, 400, 800, 1600, and 3200 nematodes/plant. While it had no impact on pea grain yield, D. weischeri slightly reduced plant height, aboveground biomass, and pod length at the population densities of 1600 and 3200 nematodes/plant. The final population densities at harvest were not significantly different from the initial densities indicating the pea varieties were poor hosts to D. weischeri. The results of the present study indicate that D. weischeri is unlikely to be a pest of yellow pea for weather conditions of the Canadian Prairies. [ABSTRACT FROM AUTHOR]

The ability of the recently described stem nematode of creeping thistle (Cirsium arvense L.), Ditylenchus weischeri, to develop on and parasitize yellow pea (Pisum sativum L.) is uncertain. The current study examined nematode life-stage progression and generation time on yellow pea as affected by temperature with the related pest, D. dipsaci, used as a positive control. Relationships for body length of the two nematode species and life stage were unaffected by rearing on plant hosts compared with carrot disks. Then plant-reared J4 individuals of both nematode species were used to determine the effect of temperature (17, 22, and 27°C) on lifestage progression and minimum generation time with yellow pea. At 17 and 22°C, D. weischeri J4 individuals progressed to only the adult stage whereas, at 27°C, the minimum generation time from J4 to J4 was 30 days or 720 growing degree-days. The minimum generation time for D. dipsaci was 24, 18, and 22 days or 336, 342, and 528 growing degree-days at 17, 22, and 27°C. respectively. The results indicate that development of D. weischeri is temperature dependent and reproduction is unlikely on yellow pea in the Canadian Prairies, where mean daily air temperatures of 27°C are rare and not sustained. [ABSTRACT FROM AUTHOR]

The authors report the detection of nitrous oxide gas using intracavity fiber laser absorption spectroscopy. A gas cell based on a hollow-core photonic crystal fiber was constructed and used inside a fiber ring laser cavity as an intracavity gas cell. The fiber laser in the 1.55 μm band was developed using a polarization-maintaining erbium-doped fiber as the gain medium. The wavelength of the laser was selected by a fiber Bragg grating (FBG), and it matches one of the absorption lines of the gas under investigation. The laser wavelength contained multilongitudinal modes, which increases the sensitivity of the detection system. N2O gas has overtones of the fundamental absorption bands and rovibrational transitions in the 1.55 μm band. The system was operated at room temperature and was capable of detecting nitrous oxide gas at sub-ppmv concentration level. [ABSTRACT FROM AUTHOR]

Agricultural management practices impact the bacterial diversity of soil but it is unclear how bacterial communities respond to different nutrient sources. This study examined the impacts of manure and granular urea N additions on the diversity and composition of soil bacterial communities. Bacterial communities in an annual cropping system were examined in the short-term (within season) and medium-term (after three successive annual additions) following manure and urea N applications. Soil samples were collected from an experimental field site in fall 2007 prior to imposition of treatments, and post-planting, mid-season, and post-harvest in 2010 following three successive annual applications. Treatments included: solid pig manure (SPM), solid dairy manure (SDM), granular urea N-fertilizer, and unamended control. Pyrosequencing was used to characterize bacterial communities in soil and the manure added. Psychrobacter was the most abundant genus in both SPM and SDM, however it was not detected in soil. Solid pig manure treatments had greater diversity than urea and control treatments and diversity was greatest at post-harvest in fall than post-planting in spring. In 2010, the relative abundances of many bacterial taxa were affected by treatment and sample season but not their interaction. Where Actinobacteria, Firmicutes, Gemmatimonadetes and Bacteroidetes were significantly different for the urea and manure treatments, Proteobacteria declined in relative abundance over the growing season. Communities of manure and urea treated soils converged with progression of growing season. Redundancy analysis showed SO 4 −2 , NO 3 − and NH 4 + concentrations were significant, explaining 44% of the variation observed in bacterial communities across treatments and sample seasons. In conclusion, bacterial diversity increased with manure treatment and with progression of the growing season, the former being not as a result of introduction of taxa from the manure but likely from nutritional resources provided in the organic amendments. [ABSTRACT FROM AUTHOR]

Anaerobic conditions induced by prolonged flooding often lead to an enhanced release of phosphorus (P) to floodwater; however, this effect is not consistent across soils. This study aimed to develop an index to predict P release potential from alkaline soils under simulated flooded conditions. Twelve unamended or manure-amended surface soils from Manitoba were analyzed for basic soil properties, Olsen P (Ols-P), Mehlich-3 extractable total P (M3PICP), Mehlich-3 extractable molybdate-reactive P (M3PMRP), water extractable P (WEP), soil P fractions, single-point P sorption capacity (P150), and Mehlich-3 extractable Ca (M3Ca), and Mg (M3Mg). Degree of P saturation (DPS) was calculated using Ols-P, M3PICP or M3PMRP as the intensity factor, and an estimated adsorption maximum based on either P150 or M3Ca + M3Mg as the capacity factor. To develop the model, we used the previously reported floodwater dissolved reactive P (DRP) concentration changes during 8 wk of flooding for the same unamended and manured soils. Relative changes in floodwater DRP concentration (DRPratio), calculated as the ratio of maximum to initial DRP concentration, ranged from 2 to 15 across ten of the soils, but were ≤1.5 in the two soils with the greatest clay content. Partial least squares analysis indicated that DPS3 calculated using M3PICP as the intensity factor and (2 × P150) + M3PICP as the capacity factor with clay percentage can effectively predict DRPratio (r2 = 0.74). Results suggest that P release from a soil to floodwater may be predicted using simple and easily measurable soil properties measured before flooding, but validation with more soils is needed. [ABSTRACT FROM AUTHOR]

Fall application of anhydrous ammonia in Manitoba is common but its impact on nitrous oxide (N2O) emissions is not well known. A 2-yr study compared application before freeze-up in late fall to spring pre-plant application of anhydrous ammonia on nitrous oxide (N2O) emissions from a clay soil in the Red River Valley, Manitoba. Spring wheat (Triticum aestivum L.) and corn (Zea mays L.) were grown on two 4-ha fields in 2011 and 2012, respectively. Field-scale flux of N2O was measured using a fluxgradient micrometeorological approach. Late fall treatment did not induce N2O emissions soon after application or in winter likely because soil was frozen. Application time did alter the temporal pattern of emissions with late fall and spring pre-plant applications significantly increasing median daily N2O flux at spring thaw and early crop growing season, respectively. The majority of emissions occurred in early growing season resulting in cumulative emissions for the crop year being numerically 33% less for late fall than spring pre-plant application. Poor yield in the first year with late fall treatment occurred because of weed and volunteer growth with delayed planting. Results show late fall application of anhydrous ammonia before freeze-up increased N2O emissions at thaw and decreased emissions for the early growing season compared to spring pre-plant application. However, improved nitrogen availability of late fall application to crops the following year is required when planting is delayed because of excessive moisture in spring. [ABSTRACT FROM AUTHOR]

The stem nematode Ditylenchus weischeri was recently reported on creeping thistle (Cirsium arvense) in Canada. Two greenhouse studies examined host suitability of crops commonly grown in the Canadian Prairies for D. weischeri and the closely related parasite of many crops, D. dipsaci. In the first study, common pulse crops (yellow pea, chickpea, common bean, and lentil), spring wheat, canola, creeping thistle, and garlic were evaluated. Plant biomass and reproductive factor (Rf = nematode recovered/inoculated) 8 weeks postinoculation were used to determine host suitability. Creeping thistle biomass was reduced by D. weischeri whereas D. dipsaci reduced biomass of four of five pea and two of three bean varieties. Two pea varieties were weak hosts for D. weischeri, with Rf slightly >1. D. weischeri aggressively reproduced on creeping thistle (Rf = 5.4). D. dipsaci reproduced aggressively on garlic (Rf = 6.4; a known host), moderately on pea varieties (Rf > 2), and weakly on chickpea and bean (Rf > 1). In the second study, using creeping thistle and yellow pea, D. weischeri was recovered from aboveground parts of the plants and seed of the former and D. dipsaci from the later. The results show that D. weischeri parasitizes creeping thistle but not other crops and that D. weischeri host preference is different from that of D. dipsaci. [ABSTRACT FROM AUTHOR]

Aside from negative impacts on crop yield, the role of weeds in agricultural systems, particularly with respect to below ground function, is not well understood. In this study, we utilised a mesocosm approach with soils collected from a long-term rotation study to compare legacy effects of previous flax ( Linum usitatissimum L.) or canola ( Brassica napus L.) and different levels of weediness established over a decade by different herbicide use patterns. Despite few significant differences in initial soil chemical properties, the impact of level of weediness superseded that of the preceding crop and altered the growth of durum wheat ( Triticum durum L.) during early development and the temporal dynamics of denitrification and the nirK denitrifier communities. The impact of the presence of durum plants in the mesocosm experiment was relatively small, however, the presence of durum plants did modify the legacy effects of preceding crop and weediness on the denitrifier community. Differences in denitrifier community structure were due to differential presence/absence and differential abundance of multiple T-RFs. To our knowledge, this is the first study to investigate the effects of long-term weed management strategies on denitrification. Our results indicate that weediness contributes to priming effects and unexplained variation associated with these soil processes and that weed management history should be taken into consideration when determining soil function and soil microbial community dynamics in agricultural systems. [ABSTRACT FROM AUTHOR]

The stem and bulb nematodes of theDitylenchus dipsaci(Kühn) Filipjev species complex are obligate endoparasites of various agricultural plants, causing stunting and swelling and resulting in significant economic losses. Recently, a new closely relatedDitylenchusspecies,D. weischeriChizhov, Borisov and Subbotin, a parasite of the cosmopolitan herbaceous perennial weed,Cirsium arvense(L.) Scop., was described. Many countries impose quarantine restrictions for the presence ofD. dipsaciin imported plant and soil materials. In the current study, we developed PCR with species-specific primers for the rapid and reliable separation ofD. weischeriandD. dipsaciusing gel electrophoresis and melting curve analysis. Species-specific primer sets were designed based on the nucleotide sequence of the heat shock protein (hsp90) gene for both nematode species. The PCR protocol was verified using samples ofD. weischeri,D. dipsaciand the closely related species,D. gigas, which parasitizes broadbean (Vicia fabaL.). The species-specific primer sets were able to detectD. weischeriandD. dipsacifrom samples containing mixtures ofDitylenchusspecies. The PCR species-specific protocol should allow for more rapid identification ofDitylenchusspecies recovered from plant materials than previously possible. [ABSTRACT FROM AUTHOR]

The effects of band placement of enhanced efficiency fertilizers (EEF) on nitrous oxide (N2O) emissions are uncertain. Placement and EEF on N2O emissions from spring wheat (Triticum aestivum L.) at two locations in Manitoba, in 2011 and 2012 were examined. Treatments were a no N control and 80 kg N ha-1 at planting of five combinations of placement and granular N source: broadcast-incorporated urea (Ureaj) and, subsurface side-banded urea (Urea M; each row side-banded), midrow-banded urea (UreaM; placement between every other set of rows), midrow-banded environmentally smart nitrogen (ESN, Agrium, Inc.) (ESNM), and midrow-banded SuperU (Koch Industries Inc.) (SuperUM). Planting in 2011 was delayed 40 d compared to 2012. Planting coincided with higher soil temperature and moisture resulting in three- to sevenfold more growing season N2O emissions (ΣN2O) in 2011 than 2012. In 2011, SuperUM and ESNM reduced ΣN2O, emission factor (EF) scaled by N-applied EF, and yield-scaled N2O emission intensity (El) by 47, 67, and 55%, respectively, compared with Ureaj. In 2011, increasing placement concentration of N in order broadcast-incorporation, side-banding, and midrow-banding tended to decrease ΣN2O, EF, and El of granular urea, but not statistically significant. The ΣN2O and nitrate exposure (NE), were significantly correlated over the site-years, indicating N availability from treatments in part determined emissions. Grain yield and crop N uptake were unaffected by sources and placement. These results suggest for early season wet and warm conditions, EEF N sources can reduce emissions compared with granular urea. Further studies are required to clarify placement effects on N2O emissions. [ABSTRACT FROM AUTHOR]

A field study was conducted to examine the influence of landscape position on greenhouse gases (GHG) accumulation in the soil profile and surface emissions from an undulating cropped field in the Prairie Pothole Region (PPR) of Manitoba. The field was segmented into four landscape elements: cropped Upper, Middle, and Lower, and uncropped Riparian. In fall 2005 and from spring-thaw through a growing season of flax (Linum usitatissimum L.) in 2006, soil concentrations of N2O, CH4, CO2, and O2 at 5-, 15-, 35-, and 65-cm depths and surface emissions were measured. Gas contents in gaseous and aqueous form were estimated at soil depths of 0 to 65 cm. Spring-thaw increased concentrations and contents of N2O at 1 5 to 35 cm in the Lower and Riparian elements, though surface emissions occurred only in the former. This suggested N2O accumulated during spring-thaw in both elements but was consumed under prolonged anaerobic conditions of the Riparian element before reaching the soil surface. For the Lower element, addition of N fertilizer to the soil surface resulted in shallow (5 cm) accumulation of N2O but higher surface emissions than at spring-thaw. The Riparian element consistently had the highest CH4 emissions. These occurred after the spring- thaw N2O emissions and with the accumulation of CH4 in the soil profile and declining O2 concentration. Soil concentrations and profile contents of CO2, as well as surface emissions, were consistently higher in the Riparian than the cropped elements and showed a similar increase with progression of the growing season. Thus, unlike N2O and CH4, CO2 was not subject to consumption processes in soil. The results suggest limiting N2O emissions in depression areas may be possible by shifting N2O production from the near soil surface to lower depths. Promotion of aeration to encourage CH4 consumption in the soil surface may lower CH4 emissions in wet years. Generally, the accumulation depth of GHG varied across the landscape elements reflecting differences in the biophysical factors controlling production and consumption and, thus, determining the surface emissions. [ABSTRACT FROM AUTHOR]

Abstract: Effects of hog slurry application to fertilized grassland on emissions of nitrous oxide (N2O) from feces and urine excreted by cattle grazing was determined. Feces from cattle grazing forage grass fertilized with two rates of plant available N from a hog slurry, (i) hog slurry as Split application in fall and spring, each 72kg N/ha (Split), and (ii) hog slurry each spring at 148kg N/ha (Single), and zero slurry (Control), were monitored in field experiments in 2004 and 2005. The slurry treatments resulted in total N of feces patches of 84 (Control), 86 (Split), and 106g N/m2 (Single). Three synthetic urine treatments of (i) 136g N/m2 (Low), (ii) 233g N/m2 (Medium), and (iii) 329g N/m2 (High) and no urine (Background) applied to simulate the range in levels possible for cattle grazing the grass fertilized with the slurry treatments were examined in 2005. Nitrous oxide emissions from feces of cattle grazing the Split and Single treatments were higher than Control. Cumulative N2O emissions from feces additions in the studies were 7, 31, and 91mg N/m2 for the Control, Single and Split treatments, respectively. Nitrous oxide emissions from feces increased with feces NO3 − and soil NH4 + concentrations, and decreased with feces and soil moisture. Cumulative N2O emissions from urine treatments were much higher than from feces, being 165, 534 and 694mg/m2. Nitrous oxide emissions from urine increased with soil NO3 −, NH4 + and NO2 − concentrations and decreased with soil moisture. Nitrous oxide emissions estimated for excreta of grazing cattle were 27g/kg of direct soil emissions for grassland receiving no slurry (Control) and 104 and 73g/kg of direct emissions of the Split and Single slurry treatments. Findings indicate direct N2O emission estimates for hog cattle grazing production systems are enhanced more by hog slurry treatment than are emissions from excreta. [Copyright &y& Elsevier]

Effect of arbuscular mycorrhizal (AM) fungus on cadmium (Cd) concentration in flax was investigated in a pot experiment. Flax inoculated with Glomus intraradices and uninoculated controls were grown in a pasteurized soil that received Cd (0, 2.5, and 10 mg kg-1) and phosphorus (P; 10 and 50 mg kg-1) additions. Root colonization was not affected by Cd addition but was reduced by high P addition. Effect of G. intraradices on Cd was evident only at low P supply. Inoculation with G. intraradices decreased shoot Cd at no or low Cd addition, which was attributed to reduced root-to-shoot Cd translocation. In contrast, G. intraradices inoculation increased shoot Cd at high Cd addition, which might be associated with the greater absorption of Cd by extraradical hyphae and lower rhizosphere pH. Our results indicate that a benefit of AM fungus in reducing Cd in crops is achievable at Cd and P concentrations commonly in agricultural soils. [ABSTRACT FROM AUTHOR]

The article discusses a study aimed at determining whether modern wheat cultivars chosen under conventional management have a reduced ability to form a symbiosis with arbuscular mycorrhizal fungi (AMF), measuring tissue P in modern and older wheat and comparing older and modern wheat cultivars for grain yield under organic management. P uptake was measured to evaluate AMF function in the wheat cultivars. The study did not support the theory that older cultivars have higher AMF colonization over modern cultivars developed under high input production.