• Authors:
    • Buckley,Cathal
    • Wall,David P.
    • Moran,Brian
    • Murphy,Paul N. C.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 102
  • Issue: 3
  • Year: 2015
  • Summary: This study uses a national farm survey which is part of the European Union (EU) Farm Accountancy Data Network (FADN) to develop environmental sustainability indicators in the use of nitrogen (N) and phosphorus (P) across a range of farm systems in the Republic of Ireland. Farm level micro data were used to calculate all inputs and outputs of N and P that cross the farm gate and to derive balances (kg ha(-1)) and overall use efficiencies across 827 farms in 2012. The sample is populated weighted to represents 71,480 farms nationally. Results indicated an average N balance of 71.0 kg ha(-1) and use efficiency of 36.7 % across the nationally representative sample. Nitrogen balances were between two and four times higher across specialist dairy farms compared to livestock rearing and specialist tillage systems. Nitrogen use efficiency was generally lowest across milk producing systems compared to livestock rearing and tillage systems. Phosphorus balance and use efficiency averaged 4.7 kg ha(-1) and 79.6 % respectively across the sample. Specialist tillage and dairying farms had higher average P balances compared to other livestock based systems. The approach developed in this analysis will form the benchmark for temporal analysis across these indicators for future nutrient balance and efficiency trends and could assist other members of the EU FADN to develop similar nationally representative indicators.
  • Authors:
    • Williams, M.
    • Maratha, P.
    • Killi, D.
    • Forristal, D.
    • Lanigan, G.
    • Osborne, B.
    • Prescher, A.
    • Helmy, M.
    • Hastings, A.
    • Abdalla, M.
    • Rueangritsarakul, K.
    • Smith, P.
    • Nolan, P.
    • Jones, M. B.
  • Source: Geoderma
  • Volume: 223-225
  • Year: 2014
  • Summary: Field management activities have significant impacts on greenhouse gas (GHG) emissions from cropland soils. In this study, the effectiveness of combining reduced tillage with a mustard cover crop (RT-CC) to mitigate present and future GHG emissions from a fertilized spring barley field in the southeast of Ireland was assessed. The field site which had a free-draining sandy loam soil with low soil moisture holding capacity, had been managed for three years prior to measurements under two different tillage systems; conventional (CT) and RT-CC. Field measurements of soil CO2, N2O and CH4 emissions, crop biomass, water filled pore space (WFPS), soil temperature and soil nitrate were made to capture both steady state conditions as well as the management events. Field data were used to validate the DNDC (DeNitrification-DeComposition) model and future GHG emissions under two sets of climate projections were predicted. Although fertilizer use was the same for both treatments the RT-CC treatment had significantly (p < 0.05) higher N2O emissions for both present and future climate. However, the inclusion of a cover crop with the RT treatment increased predicted soil organic carbon (SOC), which more than compensated for the higher N2O flux resulting in a lower total GHG balance (TGGB) compared with the CT treatment. Results show that the effectiveness of RT-CC in mitigating GHG emissions will depend crucially on the magnitude of compensatory increases in carbon dioxide uptake by the cover crop that will contribute to a reduction in the total GHG balance.
  • Authors:
    • Carroll, J.
    • Burke, B.
    • Finnan, J.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 98
  • Issue: 1
  • Year: 2014
  • Summary: Nitrogen fertilizer was applied to willow after harvest in 2011, two levels of nitrogen were applied (75; 150 kg N/ha) in addition to a control. The trial was harvested in January 2013, biomass from each treatment was burnt and emissions from combustion were quantified. Nitrogen application increased leaf nitrogen and plant height although there was no difference between the nitrogen treatments. Plant height and maximum stem diameter increased with applied nitrogen at final harvest. Nitrogen fertilization significantly increased yield by 35 % although there was no difference between the two nitrogen treatments. Stem nitrogen content did not differ significantly between treatments and there was no significant difference in NOx emissions between treatments. A life cycle assessment showed that nitrogen fertilization significantly increased net greenhouse gas benefit by up to 30 % depending on the fuel replaced. The study demonstrated that the application of relatively low levels of nitrogenous fertilizer to willow can significantly improve greenhouse gas mitigation without affecting other aspects of the environment such as air quality.
  • Authors:
    • McDonnell, K.
    • Devlin, G.
    • Murphy, F.
  • Source: GLOBAL CHANGE BIOLOGY BIOENERGY
  • Volume: 6
  • Issue: 6
  • Year: 2014
  • Summary: Willow Salix sp. is currently cultivated as a short rotation forestry crop in Ireland as a source of biomass to contribute to renewable energy goals. The aim of this study is to evaluate the energy requirements and environmental impacts associated with willow (Salix sp.) cultivation, harvest, and transport using life cycle assessment (LCA). In this study, only emissions from the production of the willow chip are included, end-use emissions from combustion are not considered. In this LCA study, three impact categories are considered; acidification potential, eutrophication potential and global warming potential. In addition, the cumulative energy demand and energy ratio of the system are evaluated. The results identify three key processes in the production chain which contribute most to all impact categories considered; maintenance, harvest and transportation of the crop. Sensitivity analysis on the type of fertilizers used, harvesting technologies and transport distances highlights the effects of these management techniques on overall system performance. Replacement of synthetic fertilizer with biosolids results in a reduction in overall energy demand, but raises acidification potential, eutrophication potential and global warming potential. Rod harvesting compares unfavourably in comparison with direct chip harvesting in each of the impact categories considered due to the additional chipping step required. The results show that dedicated truck transport is preferable to tractor-trailer transport in terms of energy demand and environmental impacts. Finally, willow chip production compares favourably with coal provision in terms of energy ratio and global warming potential, while achieving a higher energy ratio than peat provision but also a higher global warming potential.
  • Authors:
    • Smith, P.
    • Williams, M.
    • Forristal, D.
    • Lanigan, G.
    • Osborne, B.
    • Abdalla, M.
    • Jones, M. B.
  • Source: Soil Use and Management
  • Volume: 29
  • Issue: 2
  • Year: 2013
  • Summary: Conservation tillage (CT) is an umbrella term encompassing many types of tillage and residue management systems that aim to achieve sustainable and profitable agriculture. Through a global review of CT research, the objective of this paper was to investigate the impacts of CT on greenhouse gas (GHG) emissions. Based on the analysis presented, CT should be developed within the context of specific climates and soils. A number of potential disadvantages in adopting CT practices were identified, relating mainly to enhanced nitrous oxide emissions, together with a number of advantages that would justify its wider adoption. Almost all studies examined showed that the adoption of CT practices reduced carbon dioxide emissions, while also contributing to increases in soil organic carbon and improvements in soil structure.
  • Authors:
    • De Nocker, L.
    • Aertsens, J.
    • Gobin, A.
  • Source: Land Use Policy
  • Volume: 31
  • Year: 2013
  • Summary: Purpose: This paper aims at indicating the potential of agricultural measures in sequestering carbon as an option for climate change mitigation. The related value for society is estimated. Principle results: Agricultural practices like agroforestry, introducing hedges, low and no tillage and cover crops have an important potential to increase carbon sequestration. The total technical potential in the EU-27 is estimated to be 1566 million tonnes CO2-equivalent per year. This corresponds to 37% of all CO2-equivalent emissions in the EU in 2007. The introduction of agroforestry is the measure with the highest potential, i.e. 90% of the total potential of the measures studied. Taking account only of the value for climate change mitigation, the introduction of agroforestry is estimated to have a value of 282 euro/ha in 2012 that will gradually increase to 1007 euro/ha in 2030. Major conclusions: This implies that there is a huge potential which represents an important value for society in general and for the agricultural sector in specific. At the European level, only in the last few years policy makers have recognized the important benefits of agroforestry. In their rural development programmes some European countries now support farmers to introduce agroforestry. But still the current level of support is only a small fraction of the societal value of agroforestry. If this value would be fully recognized by internalizing the positive externality, we expect that agroforestry will be introduced to a very large extent in the next decades, in Europe and the rest of the world, and this will importantly change the rural landscapes. (C) 2012 Elsevier Ltd. All rights reserved.
  • Authors:
    • Humphreys, J.
    • Casey, I.
    • Necpalova, M.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 95
  • Issue: 3
  • Year: 2013
  • Summary: This study evaluated the effect of grassland renovation on soil total N, soluble N, N leaching to groundwater and nitrous oxide (N2O) fluxes from poorly drained clay loam soils on a dairy farm in Ireland. The experimental area was divided into six blocks. In June 2008, one paddock in each block was ploughed and reseeded, and subsequently compared with a permanent grassland paddock. Nitrogen in groundwater was determined in a dense network of piezometers. Soil total N along with soluble N assessed in KCl extracts were determined at three depths to 0.9 m. The N2O fluxes were measured using the static chamber technique. Renovation decreased topsoil total N and soluble organic N (P 3 t N ha(-1)), the proportion lost via N leaching and N2O emissions was unsubstantial (27.11 kg N ha(-1) y(-1)) and represented only 4.8 and 0.49 % of the N input to renovated grassland, respectively. This was likely a result of soil inherent properties and anoxic status of the soils, which likely promoted complete denitrification. Since this study was a single site study and the measurements started only months after the renovation and were relatively short term, there is some uncertainty in the results.
  • Authors:
    • Osborne, B.
    • Richards, M.
    • Khalil, M. I.
    • Williams, M.
    • Mueller, C.
  • Source: Atmospheric Environment
  • Volume: 81
  • Issue: December
  • Year: 2013
  • Summary: Model simulations of C and N dynamics, based on country-specific agricultural and environmental conditions, can provide information for compiling national greenhouse gas (GHG) inventories, as well as insights into potential mitigation options. A multi-pool dynamic model, `ECOSSE' (v5 modified), was used to simulate coupled GHGs and soil organic carbon (SOC) stock changes. It was run for an equivalent time frame of 8 years with inputs from conventionally-tilled arable land cropped with spring barley receiving N fertilizer as calcium ammonium nitrate at 135-159 kg N ha(-1) and crop residues (3 t ha-1 yr-1). The simulated daily N2O fluxes were consistent with the measured values, with R-2 of 033 (p < 0.05) and the total error and bias differences were within 95% confidence levels. The measured seasonal N2O losses were 0.39-0.60% of the N applied, with a modelled estimate of 0.23-0.41%. In contrast, the measured annual N2O loss (integrated) was 0.35% and the corresponding simulated value of 0.45% increased to 0.59% when the sum of the daily fluxes was taken into account. This indicates intermittent gas samplings may miss the peak fluxes. On an 8-year average the modelled N2O emission factor (EF) was 0.53 0.03%. The model successfully predicted the daily heterotrophic respiration (RH), with an R-2 of 0.45 (p <0.05) and the total error and bias differences were within the 95% confidence intervals. The simulated and measured total RH (3149 versus 3072 kg C ha(-1) yr(-1)) was within the cropland average values previously reported. The total measured CH4 fluxes indicated that the unfertilized treatments were a small source (-2.29 g C ha(-1) yr(-1)), whilst the fertilized treatments were a sink (+3.64). In contrast, the simulated values suggested a sink (26.61-31.37 g C ha(-1) yr(-1)), demonstrating fertilizer-induced decreases in CH4 oxidation. On average, based on the simulated SOC content a loss of 516 kg C ha(-1) yr(-1) was indicated, which is within the uncertainty range for temperate regions. Results suggest that the model is suitable for estimating the GHG balance of arable fields. However, further refinements and analyses to fully determine and narrow down the uncertainty ranges for GHG estimates are required. (C) 2013 Elsevier Ltd. All rights reserved.
  • Authors:
    • Giltrap, D.
    • Hernandez-Ramirez, G.
    • Kim, D.-G.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 168
  • Issue: March
  • Year: 2013
  • Summary: Rising atmospheric concentrations of nitrous oxide (N2O) contribute to global warming and associated climate change. It is often assumed that there is a linear relationship between nitrogen (N) input and direct N2O emission in managed ecosystems and, therefore, direct N2O emission for national greenhouse gas inventories use constant emission factors (EF). However, a growing body of studies shows that increases in direct N2O emission are related by a nonlinear relationship to increasing N input. We examined the dependency of direct N2O emission on N input using 26 published datasets where at least four different levels of N input had been applied. In 18 of these datasets the relationship of direct N2O emission to N input was nonlinear (exponential or hyperbolic) while the relationship was linear in four datasets. We also found that direct N2O EF remains constant or increases or decreases nonlinearly with changing N input. Studies show that direct N2O emissions increase abruptly at N input rates above plant uptake capacity. The remaining surplus N could serve as source of additional N2O production, and also indirectly promote N2O production by inhibiting biochemical N2O reduction. Accordingly, we propose a hypothetical relationship to conceptually describe in three steps the response of direct N2O emissions to increasing N input rates: (1) linear (N limited soil condition), (2) exponential, and (3) steady-state (carbon (C) limited soil condition). In this study, due to the limited availability of data, it was not possible to assess these hypothetical explanations fully. We recommend further comprehensive experimental examination and simulation using process-based models be conducted to address the issues reported in this review. (C) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • Dauber, J.
    • Zimmermann, J.
    • Jones, M. B.
  • Source: GCB Bioenergy
  • Volume: 4
  • Issue: 4
  • Year: 2012
  • Summary: The use of biomass for energy production is considered a promising way to reduce net carbon emissions and mitigate climate change. However, land-use change to bioenergy crops can result in carbon emissions from soil and vegetation in amounts that could take decades to compensate. Perennial grasses such as Miscanthus offer a possible solution to this problem as measurements on experimental plots planted with Miscanthus have shown significant carbon sequestration in the soil. It can, however, be expected that sequestration potentials in commercial use might differ from those measured in experimental plots due to different farming practices and soil characteristics. For this study, Miscanthus plantations on 16 farms in SE Ireland as well as on-farm controls representing the former land-use (grassland and tillage) have been examined. The Miscanthus plantations were 2-3 years old. Soil organic carbon (SOC) content and a number of soil properties were measured and the amount of Miscanthus-derived carbon was determined using the 13C natural abundance method. On both former tillage fields and grasslands, although there were no significant differences in SOC contents between Miscanthus and control sites, it was shown that 2-3 years after Miscanthus establishment, 1.821.69 and 2.171.73 Mg ha -1 of the SOC under former-tilled and former grassland respectively were Miscanthus-derived. Mixed-effects models were used to link the total SOC concentrations and Miscanthus-derived carbon to the land-use parameters as well as to soil properties. It was shown that on control sites, pH had an effect on total SOC. In the case of Miscanthus-derived carbon, the initial SOC content, pH, former land-use and crop age had significant effects.