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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]

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]

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.