TIME LAG IN EFFECTS OF MITIGATION MEASURES ON PHOSPHORUS LOSS ACROSS THE TRANSFER CONTINUUM IN A MONITORED DAIRY GRASSLAND CATCHMENT

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1 TIME LAG IN EFFECTS OF MITIGATION MEASURES ON PHOSPHORUS LOSS ACROSS THE TRANSFER CONTINUUM IN A MONITORED DAIRY GRASSLAND CATCHMENT P.N.C. Murphy, P.-E. Mellander, A.R. Melland, C. Buckley, M. Shore, G. Shortle, D. Wall, M. Treacy, O. Shine, S. Mechan, P. Jordan

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3 Context EU Nitrates and Water Framework Directives Ireland- P included in NAP EU milk quotas ended April this year Food Harvest % dairy output Intensification Water Quality? Sustainability?

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6 P Balance and Losses Imports Exports Loss

7 Catchment

8 Catchment 42 land owners farmers- most area 12 in derogation (>2 LU ha -1 ) (34% area) Overall stocking rate 1.94 LU ha -1 (165 kg organic N ha -1 ) Arable Land Use Other 10% 15% 75% Grassland

9 Well Drained Imperfectly Drained Poorly Drained Well drained Imperfectly drained Poorly drained Typical Brown Earth Typical Brown Alluvial Soil Stagnic Brown Earth Gleyic Brown Alluvial Surface-water Gley Peat Meters

10 Farm P Balance 9 dairy, 1 suckler, 1 mixed tillage % catchment area Dairy Farm Average- 61 ha 92% grassland whole-farm stocking rate 2.4 LU ha -1 milk production 9761 l ha -1 dairy gross margin return 3130 ha -1 top 10% nationally

11 Dairy Farm P Balance kg ha -1 yr -1 Imports Exports 9.7 ( ) 9.3 ( ) 6.2 (0 12.7) 0.3 (0-1.5) (2.4 6) 0.1 (0 1.2) Balance = (-3-8) PUE = 89% (59 126%)

12 International Comparison Australia Irelandthis study Source: Gourley, C. J., Dougherty, W. J., Weaver, D. M., Aarons, S. R., Awty, I. M., Gibson, D. M.,... & Peverill, K. I. (2012). Farm-scale nitrogen, phosphorus, potassium and sulfur balances and use efficiencies on Australian dairy farms. Animal Production Science, 52(10),

13 Sources: Mounsey, J., Sheehy, J., Carton, O. T., & O Toole, P Nutrient management planning on Irish dairy farms. End of project report, ARMIS, Treacy, M., Nutrient management on intensive dairy farms in the South-West of Ireland. Masters Thesis, Queen's University, Belfast, Northern Ireland. Mihailescu, E., Murphy, P. N. C., Ryan, W., Casey, I. A., & Humphreys, J. (2015). Phosphorus balance and use efficiency on 21 intensive grass-based dairy farms in the South of Ireland. The Journal of agricultural science, 153(03), Buckley, C., Murphy, P., Wall, D., Farm-gate N and P balances and use efficiencies across specialist dairy farms in the Republic Ireland (online). Teagasc Rural Economy Working Paper. Available at: Trends Nitrate Nitrate Regulations Regulations P Balance kg ha -1 yr P Fertiliser n=12 n=21 n=21 n=195 n=

14 Fertiliser Use in Ireland -16% -30% -38% -63% -48% -41% -46% -55% -48% Source: Lalor et al. 2010

15 Optimal P Balance kg ha -1 yr -1 Imports Exports 9.7 ( ) 9.3 ( ) 6.2 (0 12.7) 0.3 (0-1.5) Optimal Balance = ( ) 4.3 (2.4 6) 0.1 (0 1.2)

16 Form of P Applied 11% 89% Organic Inorganic

17 Jan C Jan O Feb Mar Apr May Jun Jul Aug Sep Oct O Oct C Nov Dec Jan C Jan O Feb Mar Apr May Jun Jul Aug Sep Oct O Oct C Nov Dec Phosphorus applied (%) Timing of P Application % 67%

18 Areal Proportion (%) Soil P Status Index 1 Index 2 Index 3 Index

19 Closed Period Stream P Concentrations

20 Stream Biological Water Quality Post Summer No clear trend over 5 years Post Winter Good Seasonal trends stronger than inter-annual Moderate Poor

21 Time Lag Nutrient Transfer Continuum Source Mobilisation Transport Delivery Impact??

22 Key Agronomic Messages P budget now very tight- requires good management Attention to soil P status Slurry/manure management Timing and location of P application Precision Nutrient Management: paddock scale at least

23 Key Environment Messages Positive trends in P source management Possible response in P concentrations in shallower water flow pathways during the winter months No clear trends in stream biological water quality Impact of management practices sooner closer to P sources on-farm - improvements in stream water quality delayed - Time Lag

24 Take-Home Messages Improvements in nutrient management may be slow to convert to definite improvements in stream water quality Stick with the established measures and water quality improvements should follow in time ND measures effective in improving P management on dairy farms Achieved with production and economic performance comparable to top 10% nationally- bodes well for dairy expansion Farmers should focus on implementing these measures as best they can -optimising nutrient management at the field/paddock scale -Precision Nutrient Management Slurry/soiled water/manure management NB This sort of intensive monitoring is probably necessary to effectively monitor and evaluate such NAPs