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Dr Bill Cotching Tasmanian Institute of Agricultural Research

Managing our Land and Water Resources A research perspective. Dr Bill Cotching Tasmanian Institute of Agricultural Research. Tasmanian catchments are different. Landuse Rainfall Elevation Relief or Topography Soil types River channel length Drainage Geology Roads & tracks

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Dr Bill Cotching Tasmanian Institute of Agricultural Research

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  1. Managing our Land and Water Resources A research perspective Dr Bill Cotching Tasmanian Institute of Agricultural Research

  2. Tasmanian catchments are different Landuse Rainfall Elevation Relief or Topography Soil types River channel length Drainage Geology Roads & tracks Irrigation Riparian zone extent

  3. Society’s perception has grown of the relationship between agricultural activity and the quality of the environment

  4. Landscape Logic

  5. Soil and water nutrients research 3 Scales of investigation Catchment Farm/paddock Plot

  6. Catchment scale nutrient generation to waterways in Northern Tasmania Landscape Logic

  7. Catchment scale nutrient generation to waterways in Northern Tasmania Landscape Logic

  8. Fertiliser application rates in 2003/04 in one Tasmanian catchment dominated by dairy farming Average Range Average loss to (kg/ha) (kg/ha) waterways (kg/ha/yr) Nitrogen 116 9 - 392 25 Phosphorus 44 16 - 76 10

  9. Farm / paddock scale

  10. Nutrient losses in runoff from Togari experimental site 2004 – 2006 (Greg Holz) Average Range Total P losses in runoff (kg/ha/yr) 10 6 - 12 Total N losses in runoff (kg/ha/yr) 23 13 – 29 Total K losses in runoff (kg/ha/yr) 43 25 - 54 75% of P lost was in the dissolved form. Up to 98% of P was lost as dissolved P in November 2004 due to P losses following fertilizing. This one event amounted to 30% of P lost in the year.

  11. Each grazing event was followed by a period of elevated concentrations of P, NH4 and K. The principal driver of the loads of nutrient loss at this site is the volume of runoff.

  12. Lucy Burkitt and Jessica Coad 5200 ha 28 dairy farms ~ 9000 milking cows 1444 paddocks Britton’s Swamp Togari

  13. Olsen P concentration (0–75 mm) of milking paddocks across Togari and Brittons Swamp 2005/2006

  14. Summary of Montagu soil nutrient data • Results show high soil phosphorus and sulphur levels (mean Olsen P = 52, range 4 – 161) • highlights need for nutrient budgeting • Uneven nutrient distribution within farms • Each catchment likely to have unique set of issues

  15. New project with dairy industry in Duck catchmentto map soil nutrients and use farm nutrient budgets

  16. Plot scale

  17. Pasture growth response to soil Olsen P levels

  18. Mean annual (2007/08) dry matter pasture yield at the Montagu experiment site. Current catchment average

  19. What happens in the estuary ?

  20. Monatagu estuary Nitrogen concentrations were no higher than those recorded from the Black or Detention estuaries Phosphorous levels were only marginally higher. High tidal exchange restricts the accumulation of nutrients limiting the potential risk of eutrophication

  21. Montagu estuary Biological sampling found species adapted to stressed environments, particularly in the upper reaches of the estuary.

  22. Dairy farming is a nutrient leaky system

  23. Tasmanian proverb Planting many fence posts Will not stop soluble nutrients from feeding fat oysters

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