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Publication information Bioresource Technology, 91 (3): 309-315Publisher Elsevier Item record/more information http://hdl.handle.net/10197/4333 Publisher's statementThis is the author's version of a work that was accepted for publication in Bioresource Technology. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Bioresource Technology ( and 8.27 g day -1 animal -1 respectively (P 0.001). There was no significant difference in the average daily intake and the average daily gain for the four diets (P>0.05).Manipulation of dietary crude protein levels would appear to offer a low cost alternative, in relation to end of pipe treatments, for the abatement of odour and ammonia emissions from finishing pig houses.

Traditionally, nutrient management has been concerned with optimizing the economic return from nutrients used for crop production. Today, the agronomic and economic requirements of nutrient management remain central, but in addition, the process must consider the potential impact of these nutrients on environmental quality. The nutrient‐management process is critical for maximizing the economic benefit from nutrients while minimizing the environmental impact. This process includes assessment, analysis, decision making, evaluation and refinement. A tactical nutrient‐management plan developed from this process must be based on a firm set of strategic objectives agreed upon by the farmers and society. The nutrient‐management process must also be practical to implement, if the performance goals are to be met. While nutrient‐management plans have resulted in benefits to farmers and society, implementation has not been as great as desired. Several factors have been identified as key to the successful implementation of nutrient‐management planning: the full participation of a broad range of stakeholders, the use of established infrastructure, targeted nutrient‐management planning efforts, voluntary vs. mandatory programs, and the economics of nutrient management. Experiences in Pennsylvania, the Republic of Ireland, and Northern Ireland illustrate aspects of the implementation of the nutrient management process.

Agriculture currently accounts for 28% of national greenhouse gas emissions in Ireland. Nitrous oxide (N 2 O) emissions from agricultural soils account for 38% of this total. A 2-year study was conducted, using the chamber technique on a fertilized and grazed grassland to quantify the effect of fertilizer application rate, soil and meteorological variables on N 2 O emissions. Three N fertilizer regimes (0, 225 & 390 kg N ha -1 ) were imposed with three replicates of each treatment. Nitrogen fertilizer was applied as urea (46% N) in spring with calcium ammonium nitrate (CAN-26% N) applied in the summer (June-September). Rotational grazing was practiced using steers. Nitrous oxide emissions arising from the unfertilized plots (0 N) were consistently low. Emissions from the N-fertilized plots (225 & 390 kg N ha -1 ) were concentrated in relatively short periods (1-2 weeks) following fertilizer applications and grazing, with marked differences between treatments, relative patterns and magnitudes of emissions at different times of the year and between years. Variation in N 2 O emissions throughout both years was pronounced with mean coefficients of variation of 116% in year 1 and 101% in year 2. The study encompassed two climatologically contrasting years. As a result the N 2 O-N loss, as a percent of the N applied in the cooler and wetter 2002 (0.2-2.0%), were similar to those used for N-fertilized grasslands under the Intergovernmental Panel on Climate Change (IPCC) N 2 O emission inventory calculation methodology (1.25% ± 1). In contrast, the percentage losses in the warmer and drier 2003 (3.5-7.2%) were substantially higher.

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