Burton, David
Permanent URI for this collectionhttps://hdl.handle.net/10222/37734
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Item Open Access Controlled release fertilizer product effects on potato crop response and nitrous oxide emissions under rain-fed production on a medium-textured soil(2012-08) Zebarth, Bernie J.; Snowdon, Emily; Burton, David L.; Goyer, Claudia; Dowbenko, RayZebarth, B. J., Snowdon, E., Burton, D. L., Goyer, C. and Dowbenko, R. 2012. Controlled release fertilizer product effects on potato crop response and nitrous oxide emissions under rain-fed production on a medium-textured soil. Can. J. Soil Sci. 92: 759-769. Controlled release fertilizers and split fertilizer N applications are expected to provide plant-available nitrogen (N) in synchrony with crop requirements, which should mitigate nitrous oxide (N2O) emissions from agricultural soils. This study compared a polymer coated urea (PCU) controlled release N fertilizer (Environmentally Smart Nitrogen), split fertilizer N application and conventional fertilizer N management on the crop response and growing season N2O emissions from rain-fed potato (Solanum tuberosum L.) production on a medium-textured soil in Atlantic Canada from 2008 to 2010. Fertilizer were applied at the recommended rate (193 kg N ha(-1)) and treatments included the PCU product banded at planting, conventional fertilizer in a split application (60% as diammonium phosphate plus ammonium nitrate at planting plus 40% as ammonium nitrate at final hilling), conventional fertilizer (diammonium phosphate plus ammonium nitrate) banded at planting, and an unfertilized control. Within each year, cumulative growing season N2O emissions were closely related to soil nitrate availability as measured by nitrate exposure (sum of daily nitrate concentration in the surface soil). Split N application had no effect on crop response, and significantly reduced nitrate exposure, but did not reduce N2O emissions. With the PCU, there was evidence of increased plant N availability and greater N2O emissions. In situations where the risk of nitrate leaching is limited, substitution of a PCU product for conventional fertilizer at the same N application rate will not necessarily reduce growing season N2O emissions and may in some cases increase the risk of N2O emissions. Further research is required to determine if lowering N rates with PCU products will be effective agronomically and environmentally.Item Open Access Changes in bacterial denitrifier community abundance over time in an agricultural field and their relationship with denitrification activity(2008-10) Dandie, Catherine E.; Burton, David L.; Zebarth, Bernie J.; Henderson, Sherri L.; Trevors, Jack T.; Goyer, ClaudiaThis study measured total bacterial and denitrifier community abundances over time in an agricultural soil cropped to potatoes (Solanum tuberosum L.) by using quantitative PCR. Samples were collected on 10 dates from spring to autumn and from three spatial locations: in the potato "hill" between plants (H), close to the plant (Hp), and in the "furrow" (F). The denitrification rates, N(2)O emissions, and environmental parameters were also measured. Changes in denitrifier abundance over time and spatial location were small (1.7- to 2.7-fold for the nirK, nosZ, and cnorB(B) guilds), whereas the cnorB(P) community (Pseudomonas mandelii and closely related spp.) showed an similar to 4.6-fold change. The seasonal patterns of denitrifier gene numbers varied with the specific community: lower nosZ gene numbers in April and May than in June and July, higher cnorB(P) gene numbers in May and June than in March and April and September and November, higher nirK gene numbers in early spring than in late autumn, and no change in cnorB(B) gene numbers. Gene numbers were higher for the Hp than the H location for the nosZ and nirK communities and for the cnorB(P) community on individual dates, presumably indicating an effect of the plant on denitrifier abundance. Higher cnorB(P) gene numbers for the H location than the F location and for nosZ and cnorB(B) on individual dates reflect the effect of spatial location on abundance. Denitrifier abundance changes were not related to any environmental parameter, although a weak relationship exists between cnorB(P) gene numbers, extractable organic carbon values, and temperature. Denitrification and N(2)O emissions were mostly regulated by inorganic nitrogen availability and water-filled pore space but were uncoupled from denitrifier community abundances measured in this system.Item Open Access Nitric oxide reductase-targeted real-time PCR quantification of denitrifier populations in soil(American Society for Microbiology, 2007-07) Dandie, C. E.; Miller, M. N.; Burton, D. L.; Zebarth, B. J.; Trevors, J. T.; Goyer, C.The quantification of denitrifying bacteria is a component in the further understanding of denitrification processes in the environment. Real-time PCR primers were designed to target two segments of the denitrifier population (cnorB(P) [Pseudomonas mandelii and closely related strains] and cnorB(B) [Bosea, Bradyrhizobium, and Ensifer spp.]) in agricultural soils based on functional cnorB (nitric oxide reductase) gene sequences. Total population numbers were measured using 16S rRNA gene real-time PCR. Two soil microcosm experiments were conducted. Experiment 1 examined the response of the indigenous soil microbial population to the addition of 500 mg/kg glucose-C daily over 7 days in soil microcosms. Changes in the total population were correlated (r = 0.83) between 16S rRNA gene copy numbers and microbial biomass carbon estimates. Members of the cnorB(P) population of denitrifiers showed typical r-strategy by being able to increase their proportion in the total population from starting levels of < 0.1% to around 2.4% after a daily addition of 500 mg/kg glucose-C. The cnorB. guild was not able to increase its relative percentage of the total population in response to the addition of glucose-C, instead increasing copy numbers only in proportion with the total population measured by 16S rRNA genes. Experiment 2 measured population dynamics in soil after the addition of various amounts of glucose-C (0 to 500 mg/kg) and incubation under denitrifying conditions. cnorB(P) populations increased proportionally with the amount of glucose-C added (from 0 to 500 mg/kg). In soil microcosms, denitrification rates, respiration, and cnorB(P) population densities increased significantly with increasing rates of glucose addition. cnorBB guild densities did not increase significantly under denitrifying conditions in response to increasing C additions.Item Open Access Permeable Synthetic Covers for Controlling Emissions from Liquid Dairy Manure(American Society of Agricultural and Biological Engineers, 2010-03) VanderZaag, A. C.; Gordon, R. J.; Jamieson, R. C.; Burton, D. L.; Stratton, G. W.Liquid manure storages emit greenhouse gases (GHGs) and ammonia (NH(3)), which can have negative effects in the atmosphere and ecosystems. Installing a floating cover on liquid manure storages is one approach for reducing emissions. In this study, a permeable synthetic cover (Biocap (TM)) was tested continuously for 165-d (undisturbed storage + 3-d agitation) in Nova Scotia, Canada. Covers were installed on three tanks of batch-loaded dairy manure (1.3 m depth x 6.6 m(2) each), while three identical tanks remained uncovered (controls). Fluxes were measured using steady-state chambers. Methane (CH(4)), carbon dioxide (CO(2)), and nitrous oxide 01)0) were measured by absorption spectroscopy, and NH(3) was measured using acid traps. Results showed covered tanks consistently reduced NH(3) fluxes by approximately 90%, even though a surface crust formed on controls after about 50 days. Covers continued to reduce NH(3) flux during agitation. Covered tanks also emitted significantly less CO(2) and N(2)O than the controls (p-value <0.01). However, CH(4) fluxes were not reduced, and therefore overall GHG fluxes were not substantially reduced. Short-term trends in CH(4), CO(2), and N(2)O flux provided insight into cover function. Notably, bubble fluxes were a key component of CH(4) emissions in both treatments, suggesting the covers did not impede CH(4) transport.Item Open Access Effect of Nitrate and Acetylene on nirS, cnorB, and nosZ Expression and Denitrification Activity in Pseudomonas mandelii(American Society for Microbiology, 2009-08) Saleh-Lakha, Saleema; Shannon, Kelly E.; Henderson, Sherri L.; Zebarth, Bernie J.; Burton, David L.; Goyer, Claudia; Trevors, Jack T.Nitrate acts as an electron acceptor in the denitrification process. The effect of nitrate in the range of 0 to 1,000 mg/liter on Pseudomonas mandelii nirS, cnorB, and nosZ gene expression was studied, using quantitative reverse transcription-quantitative PCR. Denitrification activity was measured by using the acetylene blockage method and gas chromatography. The effect of acetylene on gene expression was assessed by comparing denitrification gene expression in P. mandelii culture grown in the presence or absence of acetylene. The higher the amount of NO(3)(-) present, the greater the induction and the longer the denitrification genes remained expressed. nirS gene expression reached a maximum at 2, 4, 4, and 6 h in cultures grown in the presence of 0, 10, 100, and 1,000 mg of KNO(3)/liter, respectively, while induction of nirS gene ranged from 12- to 225-fold compared to time zero. cnorB gene expression also followed a similar trend. nosZ gene expression did not respond to NO(3)(-) treatment under the conditions tested. Acetylene decreased nosZ gene expression but did not affect nirS or cnorB gene expression. These results showed that nirS and cnorB responded to nitrate concentrations; however, significant denitrification activity was only observed in culture with 1,000 mg of KNO(3)/liter, indicating that there was no relationship between gene expression and denitrification activity under the conditions tested.Item Open Access Nitric Oxide Reductase Gene Expression and Nitrous Oxide Production in Nitrate-Grown Pseudomonas mandelii(American Society for Microbiology, 2008-11) Saleh-Lakha, Saleema; Shannon, Kelly E.; Goyer, Claudia; Trevors, Jack T.; Zebarth, Bernie J.; Burton, David L.Pure cultures of Pseudomonas mandelii were incubated with or without nitrate, which acts as a substrate and an electron acceptor for denitrification. Nitric oxide reductase (cnorB) gene expression was measured using a quantitative reverse transcription-PCR, and nitrous oxide emissions were measured by gas chromatography. P. mandelii cells in either the presence or absence of nitrate demonstrated an increase in cnorB gene expression during the first 3 h of growth. The level of expression of cnorB in nitrate-amended cells remained high (average, 2.06 x 10(8) transcripts/mu g of RNA), while in untreated cells it decreased to an average of 3.63 x 10(6) transcripts/mu g of RNA from 4 to 6 h. Nitrous oxide accumulation in the headspace was detected at 2 h, and cumulative emissions continued to increase over a 24-h period to 101 mu mol in nitrate-amended cells. P. mandelii cnorB gene expression was not detected under aerobic conditions. These results demonstrate that P. mandelii cnorB gene expression was induced 203-fold at 4 h when nitrate was present in the medium. Accumulations of N2O indicated that the cNorB enzyme was synthesized and active.Item Open Access Effect of pH and Temperature on Denitrification Gene Expression and Activity in Pseudomonas mandelii(American Society for Microbiology, 2009-06) Saleh-Lakha, Saleema; Shannon, Kelly E.; Henderson, Sherri L.; Goyer, Claudia; Trevors, Jack T.; Zebarth, Bernie J.; Burton, David L.Pseudomonas mandelii liquid cultures were studied to determine the effect of pH and temperature on denitrification gene expression, which was quantified by quantitative reverse transcription-PCR. Denitrification was measured by the accumulation of nitrous oxide (N(2)O) in the headspace in the presence of acetylene. Levels of gene expression of nirS and cnorB at pH 5 were 539-fold and 6,190-fold lower, respectively, than the levels of gene expression for cells grown at pH 6, 7, and 8 between 4 h and 8 h. Cumulative denitrification levels were 28 mu mol, 63 mu mol, and 22 mu mol at pH 6, 7, and 8, respectively, at 8 h, whereas negligible denitrification was measured at pH 5. P. mandelii cells grown at 20 degrees C and 30 degrees C exhibited 9-fold and 94-fold increases in levels of cnorB expression between 0 h and 2 h, respectively, and an average 17-fold increase in levels of nirS gene expression. In contrast, induction of cnorB and nirS gene expression for P. mandelii cells grown at 10 degrees C did not occur in the first 4 h. Levels of cumulative denitrification at 10 h were 6.6 mu mol for P. mandelii cells grown at 10 degrees C and 20 degrees C and 30 mu mol for cells grown at 30 degrees C. Overall, levels of cnorB and nirS expression were relatively insensitive to pH values over the range of pH 6 to 8 but were substantially reduced at pH 5, whereas gene expression was sensitive to temperature, with induction and time to achieve maximum gene expression delayed as the temperature decreased from 30 degrees C. Low pH and temperature negatively affected denitrification activity.Item Open Access Modification of the biophysical water function to predict the change in soil mineral nitrogen concentration resulting from concurrent mineralization and denitrification(2012-08) Georgallas, Alex; Dessureault-Rompre, Jacynthe; Zebarth, Bernie J.; Burton, David L.; Drury, Craig F.; Grant, Cynthia A.Georgallas, A., Dessureault-Rompre, J., Zebarth, B. J., Burton, D. L., Drury, C. F. and Grant, C. A. 2012. Modification of the biophysical water function to predict the change in soil mineral nitrogen concentration resulting from concurrent mineralization and denitrification. Can. J. Soil Sci. 92: 695-710. Uncertainty in soil N supply is an important limitation in making crop fertilizer N recommendations. This study modified a biophysical water function developed to predict net soil N mineralization, making it possible to consider how both N mineralization and denitrification processes affect the rate of soil mineral N accumulation. Data were from a published experiment measuring changes in soil mineral N concentration in five soils of varying texture (loamy sand to clay loam) incubated for 3 mo with or without addition of red clover residue and at two levels of compaction. The biophysical water function was effective in fitting the relationship between scaled change in the rate of soil mineral N accumulation (Delta SMN) and scaled water-filled pore space (WFPSs) across soils and treatments provided that WFPSs = 1 was set to the water content at which the transition from mineralization to denitrification occurs. The water content at WFPSs = 1 varied with soil type, but not residue addition or compaction treatments, and was closely related to clay content. The k(D), parameter, which controls the denitrification term of the function, was influenced by soil type, whereas legume residue application had no significant effect on the k(D) parameter despite a twofold increase in net N mineralization. The modified biophysical water function holds promise for improving estimates of soil N supply because it can predict changes in Delta SMN in response to N mineralization and denitrification processes across a wide range of soil water contents.Item Open Access Changes in Denitrifier Abundance, Denitrification Gene mRNA Levels, Nitrous Oxide Emissions, and Denitrification in Anoxic Soil Microcosms Amended with Glucose and Plant Residues(American Society for Microbiology, 2010-04) Henderson, Sherri L.; Dandie, Catherine E.; Patten, Cheryl L.; Zebarth, Bernie J.; Burton, David L.; Trevors, Jack T.; Goyer, ClaudiaIn agricultural cropping systems, crop residues are sources of organic carbon