- Authors:
- Wei, C. F.
- Tang, X. H.
- Wang, Z. F.
- Luo, Y. J.
- Gao, M.
- Source: Pedosphere
- Volume: 18
- Issue: 5
- Year: 2008
- Summary: The effect of different tillage systems on the size distribution of aggregates and organic carbon distribution and storage in different size aggregates in a Hydragric Anthrosol were studied in a long-term experiment in Chongqing, China. The experiment included three tillage treatments: conventional tillage with rotation of rice and winter fallow (CT-r) system, no-till and ridge culture with rotation of rice and rape (RT-rr) system, and conventional tillage with rotation of rice and rape (CT-rr) system. The results showed that the aggregates 0.02-0.25 mm in diameter accounted for the largest portion in each soil layer under all treatments. Compared with the CT-r system, in the 0-10 cm layer, the amount of aggregates >0.02 mm was larger under the RT-rr system, but smaller under the CT-rr system. In the 0-20 cm layer, the organic carbon content of all fractions of aggregates was the highest under the RT-rr system and lowest under the CT-rr system. The total organic carbon content showed a positive linear relationship with the amount of aggregates with diameter ranging from 0.25 to 2 mm. The storage of organic carbon in all fractions of aggregates under the RT-rr system was higher than that under the CT-r system in the 0-20 cm layer, but in the 0-60 cm soil layer, there was no distinct difference. Under the CT-rr system, the storage of organic carbon in all fractions of aggregates was lower than that under the CT-r system; most of the newly lost organic carbon was from the aggregates 0.002-0.02 and 0.02-0.25 mm in diameter.
- Authors:
- Kay, B. D.
- Wander, M. M.
- Drury, C. F.
- Yang, X. M.
- Source: Pedosphere
- Volume: 18
- Issue: 4
- Year: 2008
- Summary: Three long-term field trials in humid regions of Canada and the USA were used to evaluate the influence of soil depth and sample numbers on soil organic carbon (SOC) sequestration in no-tillage (NT) and moldboard plow (MP) corn (Zea mays L.) and soybean (Glycine max L.) production systems. The first trial was conducted on a Maryhill silt loam (Typic Hapludalf) at Elora, Ontario, Canada, the second on a Brookston clay loam (Typic Argiaquoll) at Woodslee, Ontario, Canada, and the third on a Thorp silt loam (Argiaquic Argialboll) at Urbana, Illinois, USA. No-tillage led to significantly higher SOC concentrations in the top 5 cm compared to MP at all 3 sites. However, NT resulted in significantly lower SOC in sub-surface soils as compared to MP at Woodslee (10-20 cm, P = 0.01) and Urbana (20-30 cm, P < 0.10). No-tillage had significantly more SOC storage than MP at the Elora site (3.3 Mg C ha(-1)) and at the Woodslee site (6.2 Mg C ha(-1)) on an equivalent mass basis (1350 Mg ha(-1) soil equivalent mass). Similarly, NT had greater SOC storage than NIP at the Urbana site (2.7 Mg C ha(-1)) on an equivalent mass basis of 675 Mg ha-1 soil. However, these differences disappeared when the entire plow layer was evaluated for both the Woodslee and Urbana sites as a result of the higher SOC concentrations in NIP than in NT at depth. Using the minimum detectable difference technique, we observed that up to 1500 soil sample per tillage treatment comparison will have to be collected and analyzed for the Elora and Woodslee sites and over 40 soil samples per tillage treatment comparison for the Urbana to statistically separate significant differences in the SOC contents of sub-plow depth soils. Therefore, it is impracticable, and at the least prohibitively expensive, to detect tillage-induced differences in soil C beyond the plow layer in various soils.
- Authors:
- Price, M.
- Burton, D. L.
- Rochette, P.
- Zebarth, B. J.
- Source: Canadian Journal of Soil Science
- Volume: 88
- Issue: 2
- Year: 2008
- Summary: This study examined the effect of rate and time of fertilizer N application to corn on N2O emissions in 2 yr on commercial corn fields. All treatments received starter fertilizer at 45 and 59 kg N ha(-1) in 2004 and 2005, respectively, similar to grower practice. Treatments included a control, with no additional fertilizer N application, 75 or 150 kg N ha(-1) banded at sidedress or 150 kg N ha(-1) broadcast at emergence. There was no significant effect of N fertility treatment on corn grain or silage yield, indicating that all N applications were at or in excess of crop N requirement. Delay of fertilizer application to sidedress and reduced fertilizer N application were effective in reducing nitrate intensity, an index of soil nitrate availability calculated as the summation of daily soil NO3--N concentration for the 0- to 15-cm depth. However, there was no significant effect of N fertility treatment on cumulative N2O emissions, and nitrate intensity explained a small proportion of the variation in cumulative N2O emissions. This study provides evidence that improved fertilizer N management may not result in reduced N2O emissions under some conditions.
- Authors:
- Tyedmers, P.
- Arsenault, N.
- Pelletier, N.
- Source: Environmental Management
- Volume: 42
- Issue: 6
- Year: 2008
- Summary: We used Life Cycle Assessment to scenario
model the potential reductions in cumulative energy
demand (both fossil and renewable) and global warming,
acidifying, and ozone-depleting emissions associated with
a hypothetical national transition from conventional to
organic production of four major field crops [canola
(Brassica rapa), corn (Zea mays), soy (Glycine max), and
wheat (Triticum aestivum)] in Canada.
- Authors:
- Source: Turkish Journal of Agriculture and Forestry
- Volume: 32
- Year: 2008
- Summary: Public interest and awareness of the need for improving nutrient use efficiency is great, but nutrient use efficiency is easily
misunderstood. Four indices of nutrient use efficiency are reviewed and an example of different applications of the terminology show
that the same data set might be used to calculate a fertilizer N efficiency of 21% or 100%. Fertilizer N recovery efficiencies from
researcher managed experiments for major grain crops range from 46% to 65%, compared to on-farm N recovery efficiencies of
20% to 40%. Fertilizer use efficiency can be optimized by fertilizer best management practices that apply nutrients at the right rate,
time, and place. The highest nutrient use efficiency always occurs at the lower parts of the yield response curve, where fertilizer
inputs are lowest, but effectiveness of fertilizers in increasing crop yields and optimizing farmer profitability should not be sacrificed
for the sake of efficiency alone. There must be a balance between optimal nutrient use efficiency and optimal crop productivity.
- Authors:
- Bertrand, N.
- Chantigny, M. H.
- Angers, D. A.
- Rochette, P.
- Source: Soil Science Society of America Journal
- Volume: 72
- Issue: 5
- Year: 2008
- Summary: The anticipated benefits of increased soil C stocks on net soil-surface greenhouse gas (GHG) emissions after adoption of soil conservation practices can be offset by increases in soil N2O emissions. The objective of this study was to assess the short-term impacts of no-till (NT) on soil N2O emissions. The study was conducted in eastern Canada in the 3rd, 4th, and 5th yr after initiation of NT and fall moldboard plowing (MP) on heavy clay and gravelly loam soils. Annual emissions of N2O were exceptionally high in the heavy clay soil, varying from 12 to 45 kg N2O-N ha-1 during the 3 yr of the study. Such high emissions were probably not associated with fertilizer N inputs but rather with denitrification sustained by the decomposition of large soil organic matter stocks (192 Mg C ha-1 in the top 0.5 m). On average, NT more than doubled N2O emissions compared with MP in the heavy clay soil. The influence of plowing on N2O flux in the heavy clay soil was probably the result of increased soil porosity that maintained soil aeration and water content at levels restricting denitrification and N2O production in the top 0.20 m. In the loam soil, average emissions during the 3 yr were similar in the NT and MP plots. The results of this study indicate that the potential of NT for decreasing net GHG emissions may be limited in fine-textured soils rich in organic matter that are prone to high water content and reduced aeration.
- Authors:
- Desjardins, R. L.
- Wagner-Riddle, C.
- Pennock, D. J.
- McConkey, B. G.
- Lemke, R. L.
- Worth, D. E.
- Rochette, P.
- Source: Canadian Journal of Soil Science
- Volume: 88
- Issue: 5
- Year: 2008
- Summary: International initiatives such as the United Nations Framework Convention on Climate Change and the Kyoto Protocol require that countries calculate national inventories of their greenhouse gas emissions. The objective of the present study was to develop a country-specific (Tier II) methodology to calculate the inventory of N2O emissions from agricultural soils in Canada. Regional fertilizer-induced emission factors (EFreg) were first determined using available field experimental data. Values for EFreg were 0.0016 kg N2O-N kg-1 N in the semi-arid Brown and 0.008 kg N2O-N kg N-1 in the sub-humid Black soil zones of the Prairie region, and 0.017 kg N2O-N kg-1 N in the humid provinces of Quebec and Ontario. A function relating EFreg to the "precipitation to potential evapotranspiration" ratio was determined to estimate annual emission factors (EFeco) at the ecodistrict scale in all agricultural regions of Canada. Country-specific coefficients were also developed to account for the effect of several additional factors on soil N2O emissions. Emissions from fine-textured soils were estimated as being 50% greater than from coarse- and medium-textured soils in eastern Canada; emissions during winter and spring thaw corresponded to 40% of emissions during the snow-free season in eastern Canada; increased emissions from lower (wetter) sections of the landscape and irrigated areas were accounted for; emissions from no-till soils were 10% greater in eastern, but 20% lower in western Canada than from those under conventional tillage practices; emissions under summerfallow were estimated as being equal to those from soils under annual cropping. This country-specific methodology therefore accounts for regional climatic and land use impacts on N2O emission factors, and includes several sources/offsets that are not included in the Intergovernmental Panel on Climate Change (IPCC) default approach.
- Authors:
- Stevens, W. B.
- Jabro, J. D.
- Sainju, U. M.
- Source: Journal of Environmental Quality
- Volume: 37
- Issue: 1
- Year: 2008
- Summary: Management practices can influence soil CO2 emission and C content in cropland, which can effect global warming. We examined the effects of combinations of irrigation, tillage, cropping systems, and N fertilization on soil CO2 flux, temperature, water, and C content at the 0- to 20-cm depth from May to November 2005 at two sites in the northern Great Plains. Treatments were two irrigation systems (irrigated vs. non-irrigated) and six management practices that contained tilled and no-tilled malt barley (Hordeum vulgaris L.) with 0 to 134 kg N ha-1, no-tilled pea (Pisum sativum L.), and a conservation reserve program (CRP) planting applied in Lihen sandy loam (sandy, mixed, frigid, Entic Haplustolls) in western North Dakota. In eastern Montana, treatments were no-tilled malt barley with 78 kg N ha-1, no-tilled rye (Secale cereale L.), no-tilled Austrian winter pea, no-tilled fallow, and tilled fallow applied in dryland Williams loam (fine-loamy, mixed Typic Argiborolls). Irrigation increased CO2 flux by 13% compared with non-irrigation by increasing soil water content in North Dakota. Tillage increased CO2 flux by 62 to 118% compared with no-tillage at both places. The flux was 1.5- to 2.5-fold greater with tilled than with non-tilled treatments following heavy rain or irrigation in North Dakota and 1.5- to 2.0-fold greater with crops than with fallow following substantial rain in Montana. Nitrogen fertilization increased CO2 flux by 14% compared with no N fertilization in North Dakota and cropping increased the flux by 79% compared with fallow in no-till and 0 kg N ha-1 in Montana. The CO2 flux in undisturbed CRP was similar to that in no-tilled crops. Although soil C content was not altered, management practices influenced CO2 flux within a short period due to changes in soil temperature, water, and nutrient contents. Regardless of irrigation, CO2 flux can be reduced from croplands to a level similar to that in CRP planting using no-tilled crops with or without N fertilization compared with other management practices.
- Authors:
- Cue, R. I.
- Rochette, P.
- Gregorich, E. G.
- Whalen, J. K.
- Sey, B. K.
- Source: Soil Science Society of America Journal
- Volume: 72
- Issue: 4
- Year: 2008
- Summary: Agricultural practices affect the production and emission of CO2 and N2O from soil. The purpose of this 2-yr field study was to determine the effects of tillage (conventionally tilled [CT] and no-till [NT]) and fertilizer source (composted cattle manure and inorganic N-P-K fertilizer) on the CO2 and N2O content in soil profiles under corn (Zea mays L.) and soybean [Glycine max (L.) Merr.]. The mean CO2 and N2O gas contents (i.e., mass of gas per unit soil volume) in the soil profile were determined periodically during two field seasons by sampling the soil atmosphere using plastic tubes installed at three depths (10, 20, and 30 cm) within the crop row. The soil CO2 content was greater in CT than NT soil and in manure-amended than inorganically fertilized plots during 1 yr of the study. The soil N2O content was not affected by tillage practices or fertilizer sources. A significant autocorrelation between sampling dates in both years suggested that the CO2 and N2O contents in the soil profile were not erratic or random, but temporally dependent on site-specific factors. The peak CO2 and N2O levels were measured within 50 d after seeding, probably because soil moisture conditions slowed diffusive gas flux but were favorable for microbial activity. Fluctuations in soil CO2 and N2O contents were not related to the seasonal variation in soil temperature. At most sampling dates, there was a significant (P < 0.05) positive correlation between the CO2 and N2O content in the soil profile, suggesting similarity in the rate of gas accumulation and diffusive flux for CO2 and N2O in soils. The CO2 and N2O content in the soil profile appeared to be controlled more by soil moisture than soil temperature or agricultural practices.
- Authors:
- Li, C.
- Drury, C. F.
- Rochette, P.
- Desjardins, R. L.
- Grant, B. B.
- Smith, W. N.
- Source: Canadian Journal of Soil Science
- Volume: 88
- Issue: 2
- Year: 2008
- Summary: Process-based models play an important role in the estimation of soil N2O emissions from regions with contrasting soil and climatic conditions. A study was performed to evaluate the ability of two process-based models, DAYCENT and DNDC, to estimate N2O emissions, soil nitrate- and ammonium-N levels, as well as soil temperature and water content. The measurement sites included a maize crop fertilized with pig slurry (Quebec) and a wheat-maize-soybean rotation as part of a tillage-fertilizer experiment (Ontario). At the Quebec site, both models accurately simulated soil temperature with an average relative error (ARE) ranging from 0 to 2%. The models underpredicted soil temperature at the Ontario site with ARE from -5 to -7% for DNDC and from -5 to -13% for DAYCENT. Both models underestimated soil water content particularly during the growing season. The DNDC model accurately predicted average seasonal N2O emissions across treatments at both sites whereas the DAYCENT model underpredicted N2O emissions by 32 to 58% for all treatments excluding the fertilizer treatment at the Quebec site. Both models had difficulty in simulating the timing of individual emission events. The hydrology and nitrogen transformation routines need to be improved in both models before further enhancements are made to the trace gas routines.
