Soil biology and Biochemistry 1 (original) (raw)
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N 2 O emission from conventional and minimum-tilled soils
Biology and Fertility of Soils, 2008
In this study, we investigated N2O emissions from two fields under minimum tillage, cropped with maize (MT maize) and summer oats (MT oats), and a conventionally tilled field cropped with maize (CT maize). Nitrous oxide losses from the MT maize and MT oats fields (5.27 and 3.64 kg N2O-N ha−1, respectively) were significantly higher than those from the CT maize field (0.27 kg N2O-N ha−1) over a period of 1 year. The lower moisture content in CT maize (43% water-filled pore space [WFPS] compared to 60–65%) probably caused the difference in total N2O emissions. Denitrification was found to be the major source of N2O loss. Emission factors calculated from the MT field data were high (0.04) compared to the CT field (0.001). All data were simulated with the denitrification decomposition model (DNDC). For the CT field, N2O and N2O + N2 emissions were largely overestimated. For the MT fields, there was a better agreement with the total N2O and N2O + N2 emissions, although the N2O emissions from the MT maize field were underestimated. The simulated N2O emissions were particularly influenced by fertilization, but several other measured N2O emission peaks associated with other management practices at higher WFPS were not captured by the model. Several mismatches between simulated and measured textNH4+{\text{NH}}_4^ + textNH4+ , textNO3−{\text{NO}}_3^ - textNO3− and WFPS for all fields were observed. These mismatches together with the insensitivity of the DNDC model for increased N2O emissions at the management practices different from fertilizer application explain the limited similarity between the simulated and measured N2O emissions pattern from the MT fields.
Soil N 2 O emissions under conventional and reduced tillage methods and maize cultivation
Plant Soil and Environment, 2017
Rutkowska B., Szulc W., Szara E., Skowrońska M., Jadczyszyn T. (2017): Soil N2O emissions under conventional and reduced tillage methods and maize cultivation. Plant Soil Environ., 63: 342–347. The study concerned the determination of nitrous oxide (N2O) emissions under conventional and reduced tillage conditions. In the reduced cultivation, a soil cultivating seed drill was used for simultaneous sowing of seeds and subsurface application of fertilizer. The emission levels of the gas tested were dependent on the year of the study and the method of soil tillage, and were subject to considerable changes during the growing season. The use of reduced soil tillage significantly limited emissions of the analysed gas into the atmosphere. Depending on the year of the study, N2O emission in the reduced tillage system was from 15% to 40% lower than in the conventional system. Low levels of easily mineralized components in soil could have been the cause of the reduction in N2O emissions to the...
Soil & Tillage Research, 2021
Reduced tillage is often promoted as a method to sequester carbon (C) in soils and thus mitigate climate change. However, in certain conditions reduced tillage may increase soil nitrous oxide (N 2 O) fluxes, which may negate any climate gains from the potential storage of C in soil. To investigate how long-term applications of different manures interact with tillage effects on N 2 O fluxes during the crop rotation, we established a long-term trial in 2009 in eastern Canada, using two tillage (inversion tillage [IT]; and reduced tillage [RT],) and three fertilizer types (pig slurry, dairy slurry and a 0-N control) arranged in a split-plot design with 3 replications. The experiment was reproduced on two contrasting soil textures (silty clay and sandy loam) located approximately 900 m apart in a wheat-corn-soybean rotation. During 2016 (wheat), 2017 (corn), and 2018 (soybean) we estimated the N 2 O fluxes from each plot using manual static chambers for the growing season (April to November). Mean cumulative fluxes for the growing season ranged from 0.8 kg N 2 ON ha − 1 for the corn/control/ IT to 7.6 kg N 2 ON ha − 1 for the wheat/dairy slurry/RT in the silty clay soils and from 0.4 kg N 2 ON ha − 1 for the corn/control/IT to 3.0 kg N 2 ON ha − 1 in the corn/pig slurry/RT in the sandy loam soils. The RT increased soil N 2 O fluxes for both slurry types and the control in the clay soil (mean flux for all fertilizer treatments over both seasons were 5.5 and 2.4 kg N 2 ON ha − 1 season − 1 for the RT and IT, respectively), likely because the higher water content in the RT caused greater denitrification; while on the sandy loam the N 2 O flux was similar between the two tillage systems. Manure type had no measurable effect on the growing season N 2 O fluxes in either soil type as both provided sufficient labile N. Application of both slurries however, resulted in greater emissions than the control (P = 0.002). These findings suggest that RT on fine-textured soils in this region may not be an effective strategy to reduce GHG emissions.
Episodic N2O emissions following tillage of a legume-grass cover crop mixture
2022
Nitrogen fertilizer inputs to agricultural soils are a leading cause of nitrous oxide (N2O) emissions in the U.S. Legume cover crops are an alternative N source that can reduce agricultural N2O emissions compared to fertilizer N. However, our understanding of episodic N2O flux following cover crop incorporation by tillage is limited and has focused on single species cover crops. Our study explores whether increasing cover crop functional diversity with a legume-grass mixture can reduce pulse emissions of N2O following tillage. In a field experiment, we planted crimson clover (Trifolium incarnatum L.), cereal rye (Secale cereal L.), a clover-rye mixture, and a no-cover control at two field sites with contrasting soil fertility properties in Michigan. We hypothesized that N2O flux following tillage of the cover crops would be lower in the mixture and rye compared to the clover treatment, because rye litter can decrease N mineralization rates. We measured N2O for approximately two weeks following tillage to capture the first peak of N2O emissions in each site. Across cover crop treatments, the higher fertility site, CF, had greater cover crop biomass, twofold higher aboveground biomass N, and higher cumulative N2O emissions than the lower fertility site, KBS (413 67.5 g N2O-N ha-1 vs. 230 42.5 g N2O-N ha-1 ; P = 0.0037). There was a significant treatment effect on daily emissions at both sites. At CF, N2O fluxes were higher following clover than the control 6 days after tillage. At KBS, fluxes from the mixture were higher than rye 8 and 11 days after tillage. When controlling for soil fertility properties across sites, clover and mixture led to approximately twofold higher N2O emissions compared to rye and fallow treatments. We found partial support for our hypothesis that N2O would be lower following incorporation of the mixture than clover. However, treatment patterns differed by site, suggesting that interactions between cover crop functional types and background soil fertility influence N2O emissions during cover crop decomposition.
Plant and Soil
Emissions of N 2 O were measured following combined applications of inorganic N fertiliser and crop residues to a silt loam soil in S.E. England, UK. Effects of cultivation technique and residue application on N 2 O emissions were examined over 2 years. N 2 O emissions were increased in the presence of residues and were further increased where NH 4 NO 3 fertiliser (200 kg N ha −1) was applied. Large fluxes of N 2 O were measured from the zero till treatments after residue and fertiliser application, with 2.5 kg N 2 ON ha −1 measured over the first 23 days after application of fertiliser in combination with rye (Secale cereale) residues under zero tillage. CO 2 emissions were larger in the zero till than in the conventional till treatments. A significant tillage/residue interaction was found. Highest emissions were measured from the conventionally tilled bean (Vicia faba) (1.0 kg N 2 ON ha −1 emitted over 65 days) and zero tilled rye (3.5 kg N 2 ON ha −1 over 65 days) treatments. This was attributed to rapid release of N following incorporation of bean residues in the conventionally tilled treatments, and availability of readily degradable C from the rye in the presence of anaerobic conditions under the mulch in the zero tilled treatments. Measurement of 15 N-N 2 O emission following application of 15 N-labelled fertiliser to microplots indicated that surface mulching of residues in zero till treatments resulted in a greater proportion of fertiliser N being lost as N 2 O than with incorporation of residues. Combined applications of 15 N fertiliser and bean residues resulted in higher or lower emissions, depending on cultivation technique, when compared with the sum of N 2 O from single applications. Such interactions have important implications for mitigation of N 2 O from agricultural soils.
The influence of winter soil cover on spring nitrous oxide emissions from an agricultural soil
In temperate regions, a majority of N 2 O is emitted during spring soil thawing. We examined the influence of two winter field covers, snow and winter rye, on soil temperature and subsequent spring N 2 O emissions from a New York corn field over two years. The first season (2006e07) was a cold winter (2309 h below 0 C at 8 cm soil depth), historically typical for the region. The snow removal treatment resulted in colder soils and higher N 2 O fluxes (73.3 vs. 57.9 ng N 2 OeN cm À2 h À1 ). The rye cover had no effect on N 2 O emissions. The second season (2007e08) was a much milder winter (1271 h below freezing at 8 cm soil depth), with lower N 2 O fluxes overall. The winter rye cover resulted in lower N 2 O fluxes (5.9 vs. 33.7 ng N 2 OeN cm À2 h À1 ), but snow removal had no effect. Climate scenarios predict warmer temperature and less snow cover in the region. Under these conditions, spring N 2 O emissions can be expected to decrease and could be further reduced by winter rye crops.
Biology and Fertility of Soils, 2011
Nitrous oxide (N 2 O) emissions, soil microbial community structure, bulk density, total pore volume, total C and N, aggregate mean weight diameter and stability index were determined in arable soils under three different types of tillage: reduced tillage (RT), no tillage (NT) and conventional tillage (CT). Thirty intact soil cores, each in a 25×25-m 2 grid, were collected to a depth of 10 cm at the seedling stage of winter wheat in February 2008 from Maulde (50°3′N, 3°43′W), Belgium. Two additional soil samples adjacent to each soil core were taken to measure the spatial variance in biotic and physicochemical conditions. The microbial community structure was evaluated by means of phospholipid fatty acids analysis. Soil cores were amended with 15 kg NO 3 − -N ha −1 , 15 kg NH 4 + -N ha −1 and 30 kg ha −1 urea-N ha −1 and then brought to 65% water-filled pore space and incubated for 21 days at 15°C, with regular monitoring of N 2 O emissions. The N 2 O fluxes showed a log-normal distribution with mean coefficients of variance (CV) of 122%, 78% and 90% in RT, NT and CT, respectively, indicating a high spatial variation. However, this variability of N 2 O emissions did not show plot scale spatial dependence. The N 2 O emissions from RT were higher (p< 0.01) than from CT and NT. Multivariate analysis of soil properties showed that PC1 of principal component analysis had highest loadings for aggregate mean weight diameter, total C and fungi/bacteria ratio.
Biogeosciences Discussions, 2019
Drained organic soils are extensively used for cereal and high-value cash crop production or as grazing land, but emissions of nitrous oxide (N2O) are enhanced by the drainage and cultivation. A study was conducted to investigate the regulation of N2O emissions in a raised bog area drained for agriculture. The area has been classified as potentially acid sulfate soil, and we hypothesised that pyrite (FeS2) oxidation was a potential driver of N2O emissions through microbially mediated reduction of nitrate (NO3-). Two sites with rotational grass, and two sites with a potato crop, were 15 equipped for monitoring of N2O emissions, as well as subsoil N2O concentrations at 5, 10, 20, 50 and 100 cm depth, during spring and autumn 2015. Precipitation, air and soil temperature, soil moisture, water table (WT) depth, and soil mineral N were recorded during weekly field campaigns. In late April and early September, intact cores were collected to 1 m depth at adjacent grassland and potato sites for analysis of soil properties, which included acid volatile sulfide (AVS) and chromium-reducible sulfur (CRS) to quantify, respectively, iron monosulfide (FeS) and FeS2, as well as 20 total reactive iron (TRFe) and nitrite (NO2-). Soil organic matter composition and total reduction capacity was also determined. The soil pH varied between 4.7 and 5.4. Equivalent soil gas phase concentrations of N2O ranged from around 10 µL L-1 at grassland sites to several hundred µL L-1 at potato sites, in accordance with lower soil mineral N concentrations at grassland sites. Total N2O emissions during 152-174 days were 3-6 kg N2O-N ha-1 for rotational grass, and 19-21 kg N2O-N ha-1 for potato sites. Statistical analyses by graphical models showed that soil N2O concentration 25 in the capillary fringe was the strongest predictor for N2O emissions in spring, and for grassland sites also in the autumn. For potato sites in the autumn, nitrate (NO3-) availability in the top soil, together with temperature, were the main controls on N2O emissions. Pyrite oxidation coupled with NO3reduction could not be dismissed as a source of N2O, but the total reduction capacity of the peat soil was much higher than explained by the FeS2 concentration, and the concentrations of TRFe were much higher than pyrite concentrations. The potential for chemodenitrification being a 30 source of N2O during WT drawdown in spring is discussed. In contrast, the N2O emissions associated with rapid soil wetting and WT rise in autumn were consistent with biological denitrification. Soil N availability and seasonal WT changes were important controls of N2O emissions.