• Authors:
    • Oenema, O.
    • Silvola, J.
    • Martikainen, P.
    • Berglund, K.
    • Klemedtsson, L.
    • Kasimir-Klemedtsson, Å.
  • Source: Soil Use and Management
  • Volume: 13
  • Issue: s4
  • Year: 1997
  • Summary: The large boreal peatland ecosystems sequester carbon and nitrogen from the atmosphere due to a low oxygen pressure in waterlogged peat. Consequently they are sinks for CO2 and strong emitters of CH4. Drainage and cultivation of peatlands allows oxygen to enter the soil, which initiates decomposition of the stored organic material, and in turn CO2 and N2O emissions increase while CH4 emissions decrease. Compared to undrained peat, draining of organic soils for agricultural purposes increases the emissions of greenhouse gases (CO2, CH4, and N2O) by roughly 1t CO2 equivalents/ha per year. Although farmed organic soils in most European countries represent a minor part of the total agricultural area, these soils contribute significantly to national greenhouse gas budgets. Consequently, farmed organic soils are potential targets for policy makers in search of socially acceptable and economically cost-efficient measures to mitigate climate gas emissions from agriculture. Despite a scarcity of knowledge about greenhouse gas emissions from these soils, this paper addresses the emissions and possible control of the three greenhouse gases by different managements of organic soils. More precise information is needed regarding the present trace gas fluxes from these soils, as well as predictions of future emissions under alternative management regimes, before any definite policies can be devised.
  • Authors:
    • Smith, K. A.
    • Swan, L.
    • Parker, J.
    • Clayton, H.
    • McTaggart, I. P.
  • Source: Biology and Fertility of Soils
  • Volume: 25
  • Issue: 3
  • Year: 1997
  • Summary: The aims of this study were to assess the effectiveness of the nitrification inhibitors dicyandiamide (DCD) and nitrapyrin on reducing emissions of nitrous oxide (N2O) following application of NH4+ or NH4 +-forming fertilisers to grassland and spring barley. DCD was applied to grassland with N fertiliser applications in April and August in 1992 and 1993, inhibiting N2O emissions by varying amounts depending on the fertiliser form and the time of application. Over periods of up to 2 months following each application of DCD, emissions of N2O were reduced by 58-78% when applied with urea (U) and 41-65% when applied with ammonium sulphate (AS). Annual emissions (April to March) of N2O were reduced by up to 58% and 56% in 1992-1993 and 1993-1994, respectively. Applying DCD to ammonium nitrate (AN) fertilised grassland did not reduce emissions after the April 1993 fertilisation, but emissions following the August application were reduced. Nitrapyrin was only applied once, with the April fertiliser applications in 1992, reducing N2O emissions over the following 12 months by up to 40% when applied with U. When N fertiliser was applied in June without DCD, the DCD applied in April was still partly effective; N2O emissions were reduced 50%, 60% and 80% as effectively as the emissions following the April applications, for AS in 1993, U in 1992 and 1993, respectively. In 1992 the persistence of an inhibitory effect was greater for nitrapyrin than for DCD, increasing after the June fertiliser application as overall emissions from U increased. There was no apparent reduction in effectiveness following repeated applications of DCD over the 2 years. N2O emissions from spring barley, measured only in 1993, were lower than from grassland. DCD reduced emissions from applied U by 40% but there was no reduction with AN. The results demonstrate considerable scope for reducing emissions by applying nitrification inhibitors with NH4 + or NH4 + -forming fertilisers; this is especially so for crops such as intensively managed grass where there are several applications of fertiliser nitrogen per season, as the effect of inhibitors applied in April persists until after a second fertiliser application in June.
  • Authors:
    • Smith, K. A.
    • Swan, L.
    • Parker, J.
    • McTaggart, I. P.
    • Clayton, H.
  • Source: Biology and Fertility of soils
  • Volume: 25
  • Issue: 3
  • Year: 1997
  • Summary: The aim was to investigate the effects of different N fertilisers on nitrous oxide (N2O) flux from agricultural grassland, with a view to suggesting fertiliser practices least likely to cause substantial N2O emissions, and to assess the influence of soil and environmental factors on the emissions. Replicate plots on a clay loam grassland were fertilised with ammonium sulphate (AS), urea (U), calcium nitrate (CN), ammonium nitrate (AN), or cattle slurry supplemented with AN on three occasions in each of 2 years. Frequent measurements were made of N2O flux and soil and environmental variables. The loss of N2O-N as a percentage of N fertiliser applied was highest from the supplemented slurry (SS) treatment and U, and lowest from AS. The temporal pattern of losses was different for the different fertilisers and between years. Losses from U were lower than those from AN and CN in the spring, but higher in the summer. The high summer fluxes were associated with high water-filled pore space (WFPS) values. Fluxes also rose steeply with temperature where WFPS or mineral N values were not limiting. Total annual loss was higher in the 2nd year, probably because of the rainfall pattern: the percentage losses were 2.2, 1.4, 1.2, 1.1 and 0.4 from SS, U, AN, CN and AS, respectively. Application of U in the spring and AN twice in the summer in the 2nd year gave an average emission factor of 0.8% - lower than from application of either individual fertiliser. We suggest that similar varied fertilisation practices, modified according to soil and crop type and climatic conditions, might be employed to minimise N2O emissions from agricultural land.
  • Authors:
    • Barra, J. D. E.
    • Carretera, A. R. H.
    • Oleschko, K.
  • Source: Soil & Tillage Research
  • Volume: 37
  • Issue: 1
  • Year: 1996
  • Summary: Little is known about the crop influence and the long-term effects of tillage systems on physical and morphological properties of Vertisols in the high plateau of the intertropical zone of Mexico. The purpose of the present study was to evaluate the impact of crop rotation on the development of structure and pedofeatures of Eutric Vertisols of Guanajuato, Mexico. Disturbed and undisturbed samples from the top soil (0-20 cm) of five agroecosystems differing in crop rotation (semipermanent alfalfa, two cereal crops per year, one vegetable and one cereal crop per year, three vegetable crops per year, and dryland maize) were collected. A second no-till soil sample was obtained from a nearby site under secondary vegetation and used as reference soil. Continuous and intensive cultivation lead to a significant reduction in Vertisol organic matter and total nitrogen contents. Tillage and crop rotations affected air-dried aggregate bulk densities, soil microstructure and development of pedofeatures. Calcite crystalline pedofeatures seemed to be more directly affected by the management systems used. Nodules, the most common crystalline pedofeatures in top soil of all cultivated Vertisols, were absent in no-till soils.
  • Authors:
    • Maclaren, P.
  • Source: Global Environmental Change
  • Volume: 40
  • Year: 1996
  • Authors:
    • Rands, M. R. W.
  • Source: Ibis
  • Volume: 128
  • Issue: 1
  • Year: 1986
  • Summary: Field experiments were carried out to test the effects of cereal pesticides (herbicides, fungicides and insecticides) on chick survival of Grey Partridge Perdix perdix, Red-legged Partridge Alectoris rufa and Pheasant Phasianus colchicus. On fields in experimental plots the outer 6 m of cereal (the headland) were not sprayed with pesticides from 1 January 1984, whereas control plots were fully sprayed. Gamebird brood counts were carried out after the cereal harvest. In addition, nine Grey Partridge broods were radio-tracked for 21 days after hatching (four in sprayed plots and five in unsprayed plots) to determine their movements, home range size and survival in relation to pesticide spraying. The mean brood size of Grey Partridge and Pheasant was significantly higher on plots where field edges were unsprayed than on fully sprayed control plots. Data for Red-legged Partridge were inconclusive. The survival of individually marked Grey Partridge broods was negatively related to the distance moved between successive nocturnal roost sites. Survival was significantly higher, the distance moved between roost sites significantly shorter and the proportion of home range including headland significantly greater for broods feeding in spring barley fields with unsprayed field edges compared with broods feeding in fully sprayed fields.