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Dairy farming systems are a major source of nitrous oxide (N2O) emission. The aim of our study was to explore the possibilities to reduce N2O emissions from intensively managed dairy farming systems using a system analysis and literature data. Intensively managed grasslands are the dominant source of N2O emission in dairy farming systems. There are several measures to mitigate N2O emission from these grasslands, categorized in three broad groups: improved N fertilizer management, improved grassland management and improved management of livestock production. A reduction of N2O emission from intensively managed dairy farming systems up to 70% may be achieved through implementation of a package ofmeasures to improve nitrogen (N) management, including refined N fertilizer application, reduction of NH3 volatilization, restricted grazing, use of maize silage, and the use of clover as an alternative for N fertilizer. [ABSTRACT FROM AUTHOR]

Nitrate leaching from a double-cropping forage system was measured over a 2-year period (June 1994-May 1996) in the Northwest region of Portugal using ceramic cup samplers. The crops were grown for silage making and include maize (from May to September) and a winter crop (rest of the year) consisting of a mixture of cereals and Italian ryegrass. The experiment was performed on two different sites with a history of many years under the same crop and fertiliser management, but differing in the amounts of N applied as fertiliser and by regular cattle slurry applications. The annual nitrate leaching losses measured ranged from 154 to 338 kg N ha-1. These amounts lead to annual mean concentrations between 22 and 41 mg NO-3-N L-1 in the drained water. The coarse textured soils (sandy loams) and the climatic conditions of the region with more than600 mm of drainage concentrated between October and March, tended topromote the leaching of all the nitrate-N left in the soil after themaize crop plus the N released by mineralization during the winter period. On these soils, the minimum amount of drainage (necessary to provide the complete leaching of all the nitrate-N in the soil profilein the end of summer), seems to be between 300 and 400 mm. The winter crops removed important quantities of N (83-116 kg N ha-1) but, due to their late establishment in autumn they did not succeed in taking up the nitrate-N left in the soil after the maize crop. Approaches for reducing the nitrate leaching losses in this particularsystem are discussed. [ABSTRACT FROM AUTHOR]

Urine patches are considered to be important sites for nitrous oxide(N2O) production through nitrification and denitrification due to their high concentration of nitrogen (N). The aim of the present study was to determine the microbial source and size of production of N2O in different zones of a urine patch on grasslandon peat soil. Artificial urine was applied in elongated patches of 4.5 m. Four lateral zones were distinguished and sampled for four weeks using an intact soil core incubation method. Incubation of soil cores took place without any additions to the headspace to determine total N2O production, with acetylene addition to determine total denitrification (N2O +N2), and with methyl fluoride to determine the N2O produced through denitrification. Nitrous oxide production was largest in the centre and decreased towards the edge of the patch. Maximum N2O production was about 50 mg N m-2 d-1 and maximum denitrification activity was 70 mg N m-2 d- 1. Nitrification was the main N2O producing process. Nitrous oxide production through denitrification was only of significance when denitrification activity was high. Total N loss through nitrification and denitrification over 31 days was 4.1 g N per patch which was 2.2% of the total applied urine-N. [ABSTRACT FROM AUTHOR]

Methane (CH4) is the most important greenhouse gas next to CO2 and as such it contributes to the enhanced greenhouse effect. Peat soils are often considered as sources of CH4. Grasslands on the other hand are generally considered to be a net sink for atmospheric CH4. The aim of this study was twofold: (i) to quantify the net CH4 emission of intensively managed grasslands on peat soil in the Netherlands; and (ii) to assess the effects of grassland management, i.e. drainage, nitrogen (N) fertilization, and grazing versus mowing, on CH4 emission rates. Net CH4 emissions were measured weekly or biweekly for one year with vented closed flux chambers at two sites, one with a mean ground water level of 22 cm below surface and one with a mean ground water level of 42 cm. On each site there were three treatments: mowing without N application, mowing with N application, and grazing with N application. The dominating species was perennial ryegyrass (Lolium perenne L.). Net CH4 emissions were low, in general in the range of -0.2 to 0.2 mg CH4 m-2 d-1. In the relatively warm summer of 1994, consumption of atmospheric CH4 peaked at 0.4 mg m-2 d-1. On an annual basis, the sites were net consumers of atmospheric CH4. However, the consumption was small: 0.31 to 0.08 kg CH4 ha-1 yr-1. Effect of mean ground water level was significant, but small. There were no significant effects of withholding N fertilization for some years and grazing versus mowing on net CH4 emissions. We conclude that grassland managementof intensively managed grasslands on peat soil is not a suitable tool for reducing net CH4 emissions. [ABSTRACT FROM AUTHOR]