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Patrick Forrestal

Research Officer

Research Interests

I head up a Soil and Plant Nutrition focused lab of 9 including 3 postdocs and 4 PhD students. I provide impactful solutions to the Agri-Food industry and policy makers particularly in the synthetic, organic and bio-based recycled fertiliser space. For example my research on protected urea has produced a practical option for farmers and lead to its adoption on Teagasc farms as the largest single measure available for agriculture to meet its Greenhouse Gas (GHG) commitments and also reduce Ammonia emissions. My work with dung, urine and fertiliser is used by the EPA to refine national inventories of GHG and ammonia. I have a track record of providing N decision support during drought, early spring N and my work in the U.S.A., including with cover crops, is credited with reducing unnecessary N applications in cropping by circa 11,000 tonnes annually.

I am a member of the Teagasc Gaseous Emissions working group which developed the MACC along with the Bioeconomy and Grass Nutrition working groups. I ensure knowledge transfer to farmers by setting up collaborative field trials and demos with advisory staff and by writing articles for Specialists to disseminate, the Farmer’s Journal, Today’s Farm and Irish Farmer’s Monthly. 

  • Soil Science Agronomy
  • Nitrogen dynamics in agro-ecosystems
  • Gaseous Nitrogen emissions from fertiliser N, urine and dung
  • Improving crop nutrient use efficiency
  • Macro and Micronutrient bio-availability
  • Cover-cropping, no-tillage systems, and soil microbiology
  • Variety testing

Current Projects

  • Sustainable Nitrogen Fertiliser Use and Disaggregated Emissions of Nitrogen on grassland and arable systems


  • 2011      Ph.D (focus on agronomy and soil science), University of Maryland, U.S.A
  • 2005      M.Agr.Sc (focus on plant pathology and agronomy), University College Dublin, Ireland
  • 2003      B.Agr.Sc (Animal and crop production), University College Dublin, Ireland

Dr. Forrestal has published many peer reviewed scientific papers:

Patrick's Google Scholar account

Patrick's Twitter account

 Rahman, N., Henke, C., Forrestal, P.J. Efficacy of the Nitrification Inhibitor 3, 4 Dimethylpyrazol Succinic Acid (DMPSA) when Combined with Calcium Ammonium Nitrate and Ammonium Sulphate—A soil incubation experiment. 2021. Agronomy, 11, 7, 1334. https://doi.org/10.3390/agronomy11071334

 Rahman, N., Richards, K.G., Harty, M.A., Watson, C.J., Carolan, R., Krol, D., Lanigan, G.J., Forrestal, P.J. Differing effects of increasing calcium ammonium nitrate, urea and urea+ NBPT fertiliser rates on nitrous oxide emission factors at six temperate grassland sites in Ireland. Agriculture, Ecosystems & Environment. 313, 107382. https://doi.org/10.1016/j.agee.2021.107382

Žurovec, O., Wall, D.P., Brennan, F., Krol, D., Forrestal, P.J., Richards, K. 2021. Increasing soil pH reduces fertiliser derived N2O emissions in intensively managed temperate grassland. Agriculture, Ecosystems & Environment. 311, 107319. https://doi.org/10.1016/j.agee.2021.107319

Ashekuzzaman, S.M., Fenton, O., Meers, E., Forrestal, P.J. Differing Phosphorus Crop Availability of Aluminium and Calcium Precipitated Dairy Processing Sludge Potential Recycled Alternatives to Mineral Phosphorus Fertiliser. Agronomy, 11(3), 427. https://doi.org/10.3390/agronomy11030427

Nkwonta, C.G., O’Neill, M., Rahman, N. Moloney, M., Forrestal, P.J., Hogan, S.A., Richards, K.G., Cummins, E., Danaher, M. 2021. Development of One-Step Non-Solvent Extraction and Sensitive UHPLC-MS/MS Method for Assessment of N-(n-Butyl) Thiophosphoric Triamide (NBPT) and N-(n-Butyl) Phosphoric Triamide (NBPTo) in Milk. Molecules, 26, 2890. https://doi.org/10.3390/molecules26102890

O’Neill, M., Saggar, S., Richards, K., Luo, J., Singh, B.P., Mehra, P., Forrestal, P.J. 2021. Nitrous oxide emission factors in conventionally and naturally simulated cattle urine patches. Nutrient Cycling in Agroecosystems, 120, 1-19. https://doi.org/10.1007/s10705-021-10162-5

Jolly, B., Luo, J., Mehra, P., Forrestal, P.J., O'Neill, M., Richards, K.G., Singh, B.P., Bates, G., Saggar, S. 2021. Evaluation of proximal sensing technologies for mapping bovine urine patches under grazing pastures. Computers and Electronics in Agriculture, 188, 106309. https://doi.org/10.1016/j.compag.2021.106309

Gebremichael, A.W., Rahman, N., Krol, D.J., Forrestal, P.J., Lanigan, G.J., Richards, K.G. 2021. Ammonium-Based Compound Fertilisers Mitigate Nitrous Oxide Emissions in Temperate Grassland. Agronomy, 11, 1712. https://doi.org/10.3390/agronomy11091712

O'Donnell, C., Egan, A, Harrington, J., Barnett, D., Forrestal, P., Power, N. 2021. An overview on deficit and requirements of the Irish national soil phosphorus balance. Science of the Total Environment, 785, 147251. https://doi.org/10.1016/j.scitotenv.2021.147251

Ashekuzzaman, S.M., Forrestal, P.J., Richards, K.G., Daly, K., Fenton, O. 2021. Grassland Phosphorus and Nitrogen Fertiliser Replacement value of Dairy Processing Dewatered Sludge. Sustainable Production and Consumption, 25: 363-373. https://doi.org/10.1016/j.spc.2020.11.017

Byrne, M.P., Tobin, J.T., Forrestal, P.J., Danaher, M., Nkwonta, C.G., Richards, K.G., Cummins, E., Hogan, S.A. O’Callaghan, T.F. 2020. Urease and Nitrification Inhibitors—As Mitigation Tools for Greenhouse Gas Emissions in Sustainable Dairy Systems: A Review. Sustainability, 12, https://doi.org/10.3390/su12156018

Ray, A. Nkwonta, C., Forrestal, P.J., Danaher, M., Richards, K., O’Callaghan, T., Hogan, S., Cummins E. 2020. Current knowledge on urease and nitrification inhibitors technology and their safety- Reviews on environmental health, De gruyter- December 7, 2020. https://doi.org/10.1515/reveh-2020-0088

Hoekstra, N.J., Schulte, R., Forrestal, P.J., Hennessy, D., Krol, D., Lanigan, G., Müller, C., Shalloo, L., Wall, D. & Richards, K. 2020. Senarios to limit environmental nitrogen losses from dairy expansion. Science of the Total Environment 707, 134606 https://doi.org/10.1016/j.scitotenv.2019.134606

Krol, D.J., Forrestal, P.J., Wall, D., Lanigan, G.J., Sanz-Gomez, J., and Richards, K.G. 2020. Nitrogen fertilisers with urease inhibitors reduce nitrous oxide and ammonia losses, while retaining yield in temperate grassland. Science of the Total Environment, 725: 138329. https://doi.org/10.1016/j.scitotenv.2020.138329

Ashekuzzaman, S.M., Forrestal, P.J., Richards, K.G., Fenton, O. 2019. Dairy industry derived wastewater treatment sludge: generation, type and characterization of nutrients and metals for agricultural reuse. Journal of Cleaner Production 230, 1266-1275.

Select Invited, Extension and Nutrient Management Presentations

 Forrestal, P.J. 2021. Reuse of recovered P from wastewater need, challenges and opportunities. Chartered Institution of Water and Environmental Management. Phosphorus recovery and reuse from wastewater event – online – 19th May 2021

 Forrestal, P.J. 2020. Integrating new bio-based fertilisers with mineral fertilisers to meet crop and soil nutrient requirements: Challenges and Opportunities. International Fertiliser Society, Cambridge, UK webinar series – online – 3rd October 2020.

Building long-term soil health using cover crops and organic manures. Ulster Arable Society Annual Meeting, CAFRE, GreenmountCampus, Antrim, UK. 14th January 2020. Organic Manure Research and Extension/Advisory in Ireland. SEGES, The Danish National Advisory Service, Aarhus, Denmark. 4.     

Reactive Nitrogen Research at Teagasc, Johnstown Castle. USDA-ARS Dairy Agro-ecosystem working group meeting, Madison, Wisconsin, U.S.A.6.      Focusing on sustainable intensification in Irish Agriculture: research at Teagasc. Seminar at U.S. Department of Agriculture – Agricultural Research Service Beltsville, Maryland, U.S.A.

Organic Manure Research and Extension/Advisory in Ireland. SEGES, The Danish National Advisory Service, Aarhus, Denmark.

Focusing on sustainable intensification in Irish Agriculture: research at Teagasc. Seminar at U.S. Department of Agriculture – Agricultural Research Service Beltsville, Maryland, U.S.A.


  • Mary Harty
  • Leanne Roche