- Authors:
- Chen, D.
- Suter, H.
- Islam, A.
- Edis, R.
- Freney, J.
- Walker, C.
- Source: Soil Research
- Volume: 46
- Issue: 4
- Year: 2008
- Authors:
- Walker, C.
- Islam, A.
- Chen, D.
- Suter, H.
- Edis, R.
- Source: Soil The Living Skin of Planet Earth
- Year: 2008
- Authors:
- Barton, L.
- Kiese, R.
- Gatter, D.
- Butterbach-Bahl, K.
- Buck, R.
- Hinz, C.
- Murphy, D. V.
- Source: Global Change Biology
- Volume: 14
- Issue: 1
- Year: 2008
- Summary: Understanding nitrous oxide (N2O) emissions from agricultural soils in semi-arid regions is required to better understand global terrestrial N2O losses. Nitrous oxide emissions were measured from a rain-fed, cropped soil in a semi-arid region of south-western Australia for one year on a sub-daily basis. The site included N-fertilized (100 kg N ha−1 yr−1) and nonfertilized plots. Emissions were measured using soil chambers connected to a fully automated system that measured N2O using gas chromatography. Daily N2O emissions were low (−1.8 to 7.3 g N2O-N ha−1 day−1) and culminated in an annual loss of 0.11 kg N2O-N ha−1 from N-fertilized soil and 0.09 kg N2O-N ha−1 from nonfertilized soil. Over half (55%) the annual N2O emission occurred from both N treatments when the soil was fallow, following a series of summer rainfall events. At this time of the year, conditions were conducive for soil microbial N2O production: elevated soil water content, available N, soil temperatures generally >25 °C and no active plant growth. The proportion of N fertilizer emitted as N2O in 1 year, after correction for the ‘background’ emission (no N fertilizer applied), was 0.02%. The emission factor reported in this study was 60 times lower than the IPCC default value for the application of synthetic fertilizers to land (1.25%), suggesting that the default may not be suitable for cropped soils in semi-arid regions. Applying N fertilizer did not significantly increase the annual N2O emission, demonstrating that a proportion of N2O emitted from agricultural soils may not be directly derived from the application of N fertilizer. ‘Background’ emissions, resulting from other agricultural practices, need to be accounted for if we are to fully assess the impact of agriculture in semi-arid regions on global terrestrial N2O emissions.
- Authors:
- Kelly, K.
- Armstrong, R.
- Phillips, F.
- Officer, S. J.
- Source: 14th Australian Agronomy Conference
- Year: 2008
- Authors:
- Eckard, R.
- Barker-Reid, F.
- Chen, D.
- Li, Y.
- Source: Plant and Soil
- Volume: 309
- Issue: 1-2
- Year: 2008
- Authors:
- Lopez, M. V.
- Cantero-Martinez, C.
- Arrue, J. L.
- Alvaro-Fuentes, J.
- Source: Soil Science Society of America Journal
- Volume: 72
- Issue: 2
- Year: 2008
- Summary: Under semiarid conditions, soil quality and productivity can be improved by enhancing soil organic matter content by means of alternative management practices. In this study, we evaluated the feasibility of no-till (NT) and cropping intensification as alternative soil practices to increase soil organic C (SOC). At the same time, we studied the influence of these management practices on two SOC fractions (particulate organic matter C, POM-C, and the mineral-associated C, Min-C), in semiarid agroecosystems of the Ebro River valley. Soil samples were collected from five soil layers (0–5-, 5–10-, 10–20-, 20–30-, 30–40-cm depth) during July 2005 at three long-term tillage experiments located at different sites in the Ebro River valley (northeast Spain). Soil bulk density, SOC concentration and content, SOC stratification ratio, POM-C, and Min-C were measured. Higher soil bulk density was observed under NT than under reduced tillage (RT), subsoil tillage (ST), or conventional tillage (CT). At the soil surface (0–5-cm depth), the highest total SOC concentration, POM-C, and Min-C were measured under NT, followed by RT, ST, and CT, respectively. In the whole soil profile (0–40 cm), similarly, slightly greater SOC content was measured under NT than under CT with the exception of the Selvanera site, where deep subsoil tillage combined with moldboard plowing accumulated more SOC than NT. In semiarid Mediterranean agroecosystems where CT consists in moldboard plowing, NT is a viable management practice to increase SOC.
- Authors:
- Fan, T.
- Xu, M
- Song, S.
- Zhou, G.
- Ding, L.
- Source: Journal of Plant Nutrition and Soil Science
- Volume: 171
- Issue: 3
- Year: 2008
- Summary: Changes in grain yields and soil organic carbon (SOC) from a 26 y dryland fertilization trial in Pingliang, Gansu, China, were recorded. Cumulative C inputs from straw and root and manure for fertilizer treatments were estimated. Mean wheat ( Triticum aestivum L.) yields for the 18 y ranged from 1.72 t ha -1 for the unfertilized plots (CK) to 4.65 t ha -1 for the plots that received manure (M) annually with inorganic N and P fertilizers (MNP). Corn ( Zea mays L.) yields for the 6 y averaged 2.43 and 5.35 t ha -1 in the same treatments. Yields declined with year except in the CK for wheat. Wheat yields for N only declined with time by 117.8 kg ha -1 y -1 that was the highest decrease among all treatments, and that for NP declined by 84.7 kg ha -1 y -1, similar to the declines of 77.4 kg ha -1 y -1 for the treatment receiving straw and N annually and P every second year (SNP). Likewise, the corn yields declined highly for all treatments, and the declined amounts ranged from 108 to 258 kg ha -1 y -1 which was much higher than in wheat. These declined yields were mostly linked to both gradual dry weather and nutrients depletion of the soil. The N only resulted in both P and K deficiency in the soil, and soil N and K negative balances in the NP and MNP were obvious. Soil organic carbon (SOC) in the 0-20 cm soil layer increased with time except in the CK and N treatments, in which SOC remained almost stable. In the MNP and M treatments, 24.7% and 24.0% of the amount of cumulative C input from organic sources remained in the soil as SOC, but 13.7% of the C input from straw and root in the SNP, suggesting manure is more effective in building soil C than straw. Across the 26 y cropping and fertilization, annual soil-C sequestration rates ranged from 0.014 t C ha -1 y -1 for the CK to 0.372 t C ha -1 y -1 for the MNP. We found a strong linear relationship ( R2=0.74, p=0.025) between SOC sequestration and cumulative C input, with C conversion-to-SOC rate of 16.9%, suggesting these dryland soils have not reached an upper limit of C sequestration.
- 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:
- 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.
