Now showing 1 - 3 of 3
  • Publication
    Estimated nitrous oxide emissions from nitrogen fertilizer use on multispecies grassland compared to monocultures
    Grassland agriculture faces increasing demands in terms of sustainability; economic, social, and environmental. Soils are critical to sustainable agriculture, in terms of maintaining soil fertility and quality, protecting water quality and mitigating greenhouse gas (GHG) emissions. There is evidence to suggest that greater sward diversity may have benefits in this regard. We report results from SmartGrass; a three year field study at two sites in Ireland investigating grass sward diversity along a gradient from perennial ryegrass (Lolium perenne L.) monoculture to grass-legume mixes to more complex grass-legume-herb mixes of up to nine species. Results reported include estimates of nitrous oxide (N2O) emissions from fertiliser nitrogen (N), soil temperature and moisture conditions, plant-available soil N, changes in soil organic carbon (C) and plant-available phosphorus (P). Estimated direct N2O emissions from N fertiliser (g N2O-N t DM-1 ha-1 yr-1) decreased from 146 for the monoculture at 250 kg fertiliser N ha-1 yr-1 to 35 for the monoculture at 90 kg fertiliser N ha-1 yr-1, to approximately 16 for the grass-legume and grass-legume-herb mixes, also at 90 kg fertiliser N ha-1 yr-1. This was due to a combination of the grass-clover and mixed swards maintaining high DM yields at low fertiliser N input, and the fact that the fertiliser N for these treatments was applied entirely as urea. These results indicate significant potential for more diverse swards to mitigate GHG emissions from fertiliser N use in grassland agriculture.
      460
  • Publication
    Improving national mapping of critical source areas of phosphorus and nitrogen losses in Irish agricultural catchments to support policy
    Policymakers, farm advisors and water agencies require up-to-date national maps of critical source areas (CSAs) of nitrogen (N) and phosphorus (P) losses from agricultural land to improve catchment management decisions. The DiffuseTools project aimed to achieve this in Ireland by updating the existing Catchment Characterisation Tool and sub-model NCYCLE_IRL, which predicts environmental losses of N and P from the farm via surface runoff, leaching, denitrification and volatilisation. Updates included (i) using improved national maps of farm-scale source loadings as inputs, (ii) sub-field scale modelling of surface transport risk using soil topographic indices derived from 1 m and 5 m NEXTMap digital elevation models (DEMs), (iii) modelling hydrological disconnectivity from microtopography (HSA Index) and reinfiltration (SCIMAP), (iv) improving the national ditch and stream channel network used by the model by DEM extraction, and (v) using SCIMAP to improve predictions of erosion risk. The improved national source loading maps included mean nationally weighted farm-gate N and P imports (fertilizer, feed and livestock) and balance surpluses (kg/ha) calculated for each stocking rate and soil group (land use potential) category within each sector type (dairy, mixed livestock, suckler cattle, non-suckler cattle, sheep and tillage), using annual Teagasc National Farm Survey data (2008-15). Furthermore, updated national maps of soil P and atmospheric N and P deposition inputs were also used within the national source loading maps to improve model performance. National CSA maps for N and P for each pathway were then produced and evaluated using water quality monitoring data and field observations from the Environmental Protection Agency and Teagasc Agricultural Catchments Programme. These maps will be able to support sustainable intensification by informing farm and catchment management decisions such as where to cost effectively target mitigation measures to reduce environmental losses, where to distribute nutrient surpluses (to non-CSAs in nutrient deficit), and improving functional land management.
      255
  • Publication
    Benchmarking farm P and N management to improve agricultural sustainability
    Agriculture faces the challenge of achieving sustainable, profitable production while maintaining environmental quality. Conventional agricultural production is highly dependent on nutrient inputs of P and N in fertilizer and feed and poor use efficiency of these resources is associated with losses to the environment and impacts on water quality, GHG emissions, air quality, acidification and biodiversity. The AgriBenchmark project explored the possibilities for benchmarking of nutrient management performance on Irish farms.
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