Browsing by Author "Baral, Khagendra"
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Item The effect of biochar and acid activated biochar on ammonia emissions during manure storage(Elsevier, 2022-12-05) Baral, Khagendra; McIlroy, John; Lyons, Gary A.; Johnston, ChristopherAnimal manure contains valuable plant nutrients which need to be stored until field application. A significant proportion of slurry nitrogen is volatilized in the form of ammonia (NH3) during storage. This impacts human health, biodiversity, air and water quality and thus urgent action is needed to reduce NH3 emissions. In this experiment, we evaluated the NH3 emission mitigation potential of biochars derived from miscanthus (MB) and solid separated anaerobic digestate (DB), and orthophosphoric acid activated MB (AMB) and DB (ADB) as well as lightweight expanded clay aggregate (LECA) during four months of liquid manure storage. A slurry without amendment was included as a control (Ctrl). Acid activated and non-activated biochars were applied on top of the slurry maintaining a 7 mm thick surface layer, while LECA was applied in a 2 cm thick layer. NH3 emissions were measured by photoacoustic analyzer. In comparison to Ctrl, acid activated biochar decreased (p < 0.05) NH3 emissions during the slurry storage. Activated biochar reduced the emissions by 37–51% within the first month of slurry storage and achieved a 25–28% emissions reduction efficiency throughout the four month period due to the reduction in emission mitigation efficiency as the storage period progressed. LECA reduced NH3 emissions by 21% during storage. Losses of NH3 as a percentage of total ammoniacal N were 29–31% for activated biochars, 35–39% for non-activated biochars and 33% for LECA. In conclusion, acid activated biochars and LECA could be good floating-covers to mitigate NH3 emissions during manure storage, but activated biochars may have better mitigation potential than LECA.Item Interactive effects of straw management, tillage, and a cover crop on nitrous oxide emissions and nitrate leaching from a sandy loam soil(Elsevier, 2022-03-05) Taghizadeh-Toosi, Arezoo; Hansen, Elly M.; Olesen, Jørgen E.; Baral, Khagendra; Petersen, Søren O.Minimum tillage, residue recycling and the use of cover crops are key elements of conservation agriculture that play important roles in soil carbon (C) and nitrogen (N) dynamics. This study determined the long-term effects of tillage practice (conventional ploughing vs. direct seeding), straw management (retained vs. removed), and the presence of a cover crop (CC; fodder radish in this study) on nitrous oxide (N2O) emissions, nitrate (NO3−) leaching, and soil mineral N dynamics between October 2019 and June 2020. In the factorial experiment with eight treatment combinations, cumulative N2O emissions ranged from 0.04 to 0.8 kg N ha−1, whereas NO3− leaching varied between 4 and 28 kg N ha−1. The study did not find effects of straw retention on NO3− leaching or N2O emissions. No-till reduced N2O emissions by on average 46% compared to ploughing. Fodder radish reduced NO3− leaching by 80–84%, and there was little N2O emission in the presence of the cover crop; however, after termination in spring there was a flush of N2O, cumulative N2O-N averaged 0.1 and 0.5 kg N ha−1 without and with a cover crop. With information about long-term soil C retention from straw and fodder radish, an overall greenhouse (GHG) balance was calculated for each system. Without straw retention after harvest, there was always a positive net GHG emission, and the indirect N2O emission from NO3− leaching was similar to, or greater than direct N2O emissions. However, in the presence of fodder radish, the direct N2O emissions after termination were much more important than indirect emissions, and negated the C input from fodder radish. Direct seeding, straw retention and the use of a cover crop showed positive effects on N retention and/or GHG balance and could substantially improve the carbon footprint of agroecosystems on sandy soil in a wet temperate climate.Item Long-term variability in N2O emissions and emission factors for corn and soybeans induced by weather and management at a cold climate site(Elsevier, 2021-12-31) Baral, Khagendra; Jayasundara, Susantha; Brown, Shannon E.; Wagner-Riddle, ClaudiaNitrous oxide (N2O) emissions are highly variable in space and time due to the complex interplay between soil, management practices and weather conditions. Micrometeorological techniques integrate emissions over large areas at high temporal resolution. This allows identification of causes of intra- and inter-annual variability of N2O emissions and development of robust emission factors (EF). Here, we investigated factors responsible for variability in N2Oemissions during growing and non-growing seasons of corn and soybeans grown in an imperfectly drained silt loam soil, in Ontario, Canada. We used quasi-continuously (at half-hourly to hourly intervals) N2O fluxes measured via the fluxgradient technique over 11 years for corn and 5 years for soybeans and evaluated the uncertainty of default IPCC and Canada-specific EFs. In the growing season, emissions were controlled by soil nitrate content, soil moisture and temperature in the fertilized corn, while moisture and temperature regulated N2O emissions in the unfertilized soybeans. In the non-growing season, nitrogen (N) input from the crop residue did not affect the emissions, pointing to freeze-thaw cycles as mechanisms for enhanced N2O emissions. The non-growing season contribution to annual emissions was 38%in corn and 43% in soybeans. On average, annual emissions were 2.6-fold higher in corn than soybeans. Observed mean N2O EFs were 0.84% (0.12–2.02%) for growing season and 1.69% (0.29–7.32%) for yearly emissions. The growing season EF derived from long-term N2O emissions was 0.9 ± 0.14%. The interannual variability in N2O emissions and EFs can be attributed to management practices and annual weather variability. The default IPCC approach based on overall N input had poorer performance in predicting annual N2O emissions compared to the current Canadian methodology, which includes management and environmental factor in addition to N inputs. The observed emissions were further evaluated with a newly developed growing season N2O emission prediction approach for Canada. However, performance of the approach was poorer than IPCC or the current national Canadian approach. Additional tests of the new national methodology are recommended as well as consideration of non-growing season emissions.Item Mitigation of Nitrous Oxide Emissions from Rice–Wheat Cropping Systems with Sub-Surface Application of Nitrogen Fertilizer and Water-Saving Irrigation(MDPI, 2023-05-04) Gaihre, Yam Kanta; Bible, Wendie D.; Singh, Upendra; Sanabria, Joaquin; Baral, KhagendraManagement of nitrogen (N) fertilizer and irrigation can play a critical role to increase nitrogen use efficiency (NUE). However, the impacts of N application at the root zone via urea briquette deep placement (UDP) and water-saving irrigation alternate wetting and drying (AWD) on N2O emissions are not well-understood. A greenhouse study was conducted to investigate the impacts of UDP on N2O emissions, NUE, and grain yields of rice and wheat compared with broadcast prilled urea (PU). For rice, the effect of UDP was evaluated under continuous flooding (CF) and AWD, while the control (no N) and PU were tested only under CF. In rice, UDP under CF irrigation produced similar emissions to PU-CF, but UDP under AWD irrigation increased emissions by 4.5-fold compared with UDP under CF. UDP under CF irrigation increased (p < 0.05) rice grain yields and N recovery efficiency (RE) by 26% and 124% compared with PU-CF, respectively. In wheat, UDP had no effects (p > 0.05) on emissions compared with PU. However, it produced higher wheat grain yields (9%) and RE (35%) over PU. In conclusion, UDP under CF irrigation increases the RE and grain yields of rice without increasing N2O emissions, but the yield may reduce and N2O emissions may increase under AWD.Item Opportunities to reduce nitrous oxide emissions from horticultural production systems in Canada(Canadian Science Publishing, 2021-08-03) Chahal, Inderjot; Baral, Khagendra; Congreves, Kate A.; Van Eerd, Laura L.; Wagner-Riddle, ClaudiaHorticultural systems, specifically vegetable production systems, are considered intensive agricultural systems as they are characterized by high nitrogen (N) fertilizer application rate, frequent tillage, and irrigation operations. Accordingly, horticultural production in temperate climates is prone to N losses — mainly during post-harvest (during fall and winter) or pre-plant (spring) periods — such as N2O emissions and nitrate leaching. The risk for N losses is linked to low crop N use efficiency (NUE) combined with a narrow C:N and high N content of crop residues. Here we reviewed the studies conducted in Canada and similar climates to better understand the risk of N2O emission and potential agronomic management strategies to reduce N2O emissions from horticultural systems. Current knowledge on N2O emissions from horticultural systems indicate that increasing crop NUE, modifying the amount, type, time, and rate of N fertilizer inputs, and adopting cover crops in crop rotations are some of the effective approaches to decrease N2O emissions. However, there is uncertainty related to the efficiency of the existing N2O mitigation strategies due to the complex interactions between the factors (soil characteristics, type of plant species, climatic conditions, and soil microbial activity) responsible for N2O production from soil. Little research on N2O emissions from Canadian horticultural systems limits our ability to understand and manage the soil N2O production processes to mitigate the risk of N2O emissions. Thus, continuing to expand this line of research will help to advance the sustainability of Canadian horticultural cropping systems.Item Short-Term Nitrous Oxide Emissions from Cattle Slurry for Silage Maize: Effects of Placement and the Nitrification Inhibitor 3,4-Dimethylpyrazole Phosphate (DMPP)(MDPI, 2023-11-10) Taghizadeh-Toosi, Arezoo; Baral, Khagendra; Sørensen, Peter; Petersen, Søren O.; Environmental ProtectionCattle slurry is an important nitrogen source for maize on dairy farms. Slurry injection is an effective measure to reduce ammonia emissions after field application, but with higher risk of nitrous oxide emission than surface application. This study compared soil mineral nitrogen dynamics and nitrous oxide emissions with two ways of application. First, traditional injection at 25 cm spacing between rows followed by ploughing (called “non-placed slurry”), and second, injection using a new so-called goosefoot slurry injector that placed the slurry in ploughed soil as a 30 cm broad band at 10 cm depth below maize crop rows with 75 cm spacing (named “placed slurry”). Furthermore, the effect of treating slurry with the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) in Vizura® was tested with both application methods. The field experiment was conducted on a sandy loam soil in a temperate climate. Both nitrous oxide emissions, and the dynamics of soil mineral nitrogen, were monitored for eight weeks after slurry application and seeding of maize using static chambers. The level of nitrous oxide emissions was higher with non-placed compared to placed slurry (p < 0.01), mainly due to higher emissions during the first four weeks. This might be due to higher rates of nitrification and in turn stimulation of denitrification. In both placed and non-placed slurry treatments, Vizura® caused higher soil ammonium concentrations and lower nitrate concentrations (p < 0.001), particularly from 3 to 8 weeks after slurry application. The final level of soil nitrate was similar with and without the nitrification inhibitor, but higher with placed compared to non-placed slurry. Adding Vizura® to non-placed slurry reduced nitrous oxide emissions by 70% when compared to untreated slurry. Surprisingly, there was a non-significant trend towards higher cumulative emissions from placed slurry with the nitrification inhibitor compared to untreated slurry, which was due to higher emissions in the last part of the monitoring period (5–7 weeks after slurry application). Possibly, degradation of the nitrification inhibitor and nitrification activity inside the slurry band as the soil dried promoted nitrous oxide emissions by this time. In summary, placement of untreated slurry in a broad band under maize seeds reduced nitrous oxide emissions compared to non-placed slurry with more soil contact. A comparable reduction was achieved by adding a nitrification inhibitor to non-placed slurry. The pattern of nitrous oxide emissions from placed slurry treated with the inhibitor was complex and requires more investigation. The emission of nitrous oxide was highest when nitrate accumulated in soil around decomposing cattle slurry, and mitigation strategies should aim to prevent this. This study demonstrated a potential for mitigation of nitrous oxide emission by placement of cattle slurry, which may be an alternative to the use of a nitrification inhibitor.