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  • 1
    Electronic Resource
    Electronic Resource
    Nitrous oxide emission from herbicide-treated soybean (2000)
    Springer
    Biology and fertility of soils 32 (2000), S. 173-176 
    Details
    ISSN: 1432-0789
    Keywords: Key words Nitrous oxide emission ; Herbicides ; Soybean ; Dichlorophenoxyacetic acid ; Bromoxynil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The emission of N2O from soybean plants treated with the herbicides dichlorophenoxyacetic acid (2,4-D) and bromoxynil was studied. The N2O flux from 2,4-D- and bromoxynil-treated soybean was 14.1 ng N2O-N g–1 fresh weight h–1 and 19.7 ng N2O-N g–1 fresh weight h–1, respectively, i.e. approximately twice that of the controls. The NO2 –-N concentration in 2,4-D- and in bromoxynil-treated soybean was about 8 μg N g–1 fresh weight, i.e. fivefold the concentration found in control plants. The NO3 – content in herbicide-treated soybean did not differ significantly from that of the control plants. Consequently, the accumulation of NO2 –-N during the assimilation of NO3 –-N was thought to cause the observed N2O release. Probably, N2O is a by-product produced during either the reaction of NO2 –-N with plant metabolites or NO2 –-N decomposition. Final conclusions must await further experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740000235
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  • 2
    Electronic Resource
    Electronic Resource
    Carbon stock changes and carbon sequestration potential of Flemish cropland soils (2003)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 9 (2003), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: Evaluations of soil organic carbon (SOC) stocks are often based on assigning a carbon density to each one of a number of ecosystems or soil classes considered, using data from soil profiles within these categories. A better approach, in which the use of classification methods by which extrapolation of SOC data to larger areas is avoided, can only be used if enough data are available at a sufficiently small scale. Over 190 000 SOC measurements (0–24 cm) have been made in the Flemish cropland (the Northern part of Belgium) in the 1989–2000 period. These SOC data were grouped into 3-year periods and as means plus standard deviation per (part of) community (polygons). This large dataset was used to calculate SOC stocks and their evolution with time, without data extrapolation. Using a detailed soil map, larger spatial groups of polygons were created based on soil texture and spatial location. Linear regression analysis showed that in the entire study area, SOC stocks had decreased or at best had remained stable. In total, a yearly decrease of 354 kton OC yr−1 was calculated, which corresponds with a net CO2 emission of 1238 kton CO2 yr−1. Specific regions with a high carbon sequestration potential were identified, based on SOC losses during the 1989–2000 period and the mean 1999 SOC content, compared to the average SOC content of soils in Flanders with a similar soil texture. When restoring the SOC stocks to their 1990 level, we estimated the carbon sequestration potential of the Flemish cropland soils to be some 300 kton CO2 yr−1 at best, which corresponds to a 40-year restoration period. In conclusion, we can say that in regions where agricultural production is very intense, carbon sequestration in the cropland may make only a very modest contribution to a country's effort to reduce greenhouse gas emissions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2486.2003.00651.x
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  • 3
    Electronic Resource
    Electronic Resource
    Subsoils: chemo-and biological denitrification, N2O and N2 emissions (1998)
    Springer
    Nutrient cycling in agroecosystems 52 (1998), S. 187-194 
    Details
    ISSN: 1573-0867
    Keywords: chemo-denitrification ; denitrification ; nitrous oxide ; subsoil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Agricultural practices, soil characteristics and meteorological conditions are responsible for eventual nitrate accumulation in the subsoil. There is a lot of evidence that denitrification occurs in the subsoil and rates up to 60–70 kg ha-1 yr-1 might be possible. It has also been shown that in the presence of Fe2+ (formed through weathering of minerals) and an alkaline pH, nitrate can be chemically reduced. Another possible pathway of disappearance is through the formation of nitrite, which is unstable in acid conditions. With regard to the emission of N2O and N2, it can be stated that all conditions whereby the denitrification process becomes marginal are favourable for N2O formation rather than for N2. Because of its high solubility, however, an important amount of N2O might be transported with drainage water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009728125678
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  • 4
    Electronic Resource
    Electronic Resource
    Closing the global N2O budget: nitrous oxide emissions through the agricultural nitrogen cycle (1998)
    Springer
    Nutrient cycling in agroecosystems 52 (1998), S. 225-248 
    Details
    ISSN: 1573-0867
    Keywords: animal waste ; fertilizer ; greenhouse gas ; inventory ; nitrous oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In 1995 a working group was assembled at the request of OECD/IPCC/IEA to revise the methodology for N2O from agriculture for the National Greenhouse Gas Inventories Methodology. The basics of the methodology developed to calculate annual country level nitrous oxide (N2O) emissions from agricultural soils is presented herein. Three sources of N2O are distinguished in the new methodology: (i) direct emissions from agricultural soils, (ii) emissions from animal production, and (iii) N2O emissions indirectly induced by agricultural activities. The methodology is a simple approach which requires only input data that are available from FAO databases. The methodology attempts to relate N2O emissions to the agricultural nitrogen (N) cycle and to systems into which N is transported once it leaves agricultural systems. These estimates are made with the realization that increased utilization of crop nutrients, including N, will be required to meet rapidly growing needs for food and fiber production in our immediate future. Anthropogenic N input into agricultural systems include N from synthetic fertilizer, animal wastes, increased biological N-fixation, cultivation of mineral and organic soils through enhanced organic matter mineralization, and mineralization of crop residue returned to the field. Nitrous oxide may be emitted directly to the atmosphere in agricultural fields, animal confinements or pastoral systems or be transported from agricultural systems into ground and surface waters through surface runoff. Nitrate leaching and runoff and food consumption by humans and introduction into sewage systems transport the N ultimately into surface water (rivers and oceans) where additional N2O is produced. Ammonia and oxides of N (NOx) are also emitted from agricultural systems and may be transported off-site and serve to fertilize other systems which leads to enhanced production of N2O. Eventually, all N that moves through the soil system will be either terminally sequestered in buried sediments or denitrified in aquatic systems. We estimated global N2O–N emissions for the year 1989, using midpoint emission factors from our methodology and the FAO data for 1989. Direct emissions from agricultural soils totaled 2.1 Tg N, direct emissions from animal production totaled 2.1 Tg N and indirect emissions resulting from agricultural N input into the atmosphere and aquatic systems totaled 2.1 Tg N2O–N for an annual total of 6.3 Tg N2O–N. The N2O input to the atmosphere from agricultural production as a whole has apparently been previously underestimated. These new estimates suggest that the missing N2O sources discussed in earlier IPCC reports is likely a biogenic (agricultural) one.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009740530221
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  • 5
    Electronic Resource
    Electronic Resource
    Fate of urea-15N in a soil-wheat system as influenced by urease inhibitor hydroquinone and nitrification inhibitor dicyandiamide (2000)
    Springer
    Plant and soil 220 (2000), S. 261-270 
    Details
    ISSN: 1573-5036
    Keywords: dicyandiamide ; gaseous N losses ; hydroquinone ; nitrous oxide ; spring wheat ; urea-15N
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract By applying labeled urea into a loamy meadow brown soil, a pot experiment with spring wheat as test crop was carried out. The results showed that at the end of this experiment, the plant recovery, the soil recovery and the total loss of applied urea 15N was 17.7–23.7%, 43.7–56.3% and 20.0–36.8%, respectively. 15N recovery by wheat grain in any treatment varied within a range of 9.0–14.7% of the applied 15N. A combined application of hydroquinone (HQ) and dicyandiamide (DCD) gave the lowest loss and the highest recoveries in both the plant and soil, while applying HQ or DCD alone had less effect on them. During the whole period of wheat growth, HQ+DCD induced an increasing 15N uptake by plant, and even promoted the translocation of absorbed 15N from stem to grain. In the presence of inhibitors, organic plus chemically fixed 15N occupied a large portion of soil 15N recovery at maturity stage of wheat growth (34.3–50.6%, in contrast to 9.9% in the absence of inhibitors), and DCD and DCD+HQ could remarkably reduce the remaining soil (NO3 -+NO2 -)-15N. In this pot experiment, the leaching loss of applied 15N was excluded, and hence, the gaseous loss was considered as the main part of the 15N loss. Regarding N loss, N2O flux only occupied a very small part, and its main part was other gaseous N losses. DCD and DCD+HQ retarded N2O flux from the soil-wheat system after treatment with urea and reduced the total N2O flux during the whole period of wheat growth. Treatment with both inhibitors had much lower gaseous N losses than that with HQ or DCD alone. Hence, a proper combination application of HQ and DCD is an efficient way to improve urea-N efficiency and crop quality, while decreasing its loss to the environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004715827085
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