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

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

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

Landscape Logic

Soil and water nutrients research 3 Scales of investigation Catchment Farm/paddockPlot

Catchment scale nutrient generation to waterways in Northern Tasmania Landscape Logic

Catchment scale nutrient generation to waterways in Northern Tasmania Landscape Logic

Fertiliser application rates in 2003/04 in one Tasmanian catchment dominated by dairy farming Average RangeAverage loss to (kg/ha) (kg/ha)waterways (kg/ha/yr) Nitrogen Phosphorus

Farm / paddock scale

Average Range Total P losses in runoff (kg/ha/yr) Total N losses in runoff (kg/ha/yr) 2313 – 29 Total K losses in runoff (kg/ha/yr) Nutrient losses in runoff from Togari experimental site 2004 – 2006 (Greg Holz) 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.

Each grazing event was followed by a period of elevated concentrations of P, NH 4 and K. The principal driver of the loads of nutrient loss at this site is the volume of runoff.

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

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

 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 Summary of Montagu soil nutrient data

New project with dairy industry in Duck catchment to map soil nutrients and use farm nutrient budgets

Plot scale

Pasture growth response to soil Olsen P levels

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

What happens in the estuary ?

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

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

Dairy farming is a nutrient leaky system

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