Discussion on Unexpected Outcomes from Overseer Output Based on GSL Modeled Farm Production Data.

  1. Soil Type is significant in quantifying total leaching of farm and precise identification of effluent and cropping areas may significantly affect real average losses N losses for total farm. (see table 1.0)
  2. Ensuring all Soil Types are specifically identified for a particular farm may be critical in lowering Overseer’s reported N leach total for farm. (see table 2.0)
  3. N leaching for crop production particularly when grazed where grown appears to inversely reduce the cropping areas N leach when yield of crop is increased over low yielding crop. This can be very significant in quantifying the farms total average N leach per Ha. (see table 3.0)
  4. Relationship between the applied N on a reducing scale being replaced by natural N on an increasing scale but averaged annually may give an incorrect total N leach assessment relative to the real usage/benefit of the actual time of applied N use. (see table 4.0)
  5. Analysis identifies an apparent discrepancy between N applied and N “used” when pasture DM yield. Pasture yield response to applied N does not appear to be accounted for in Overseers output.
  6. Inability to identify and quantify N leach and surface water run off and drainage losses when grazing crops under wet winter conditions.
  7. Rainfall effect which increases fracleach but does this increase diminish GHG total?
  8. Cultivation effect for cropping may be a variant that can reduce leaching of N through the Overseer model.
  9. Total Milk production is the primary connection in Overseer to N leach outcomes. Is sufficient account taken of the effect per cow production will have on the N leach outcome?
  10. Overseer appears to reduce the volume of N as a less productive system introduces more applied N to the system.

1.0 Overseer N Leach Variance for Soil Type and Rainfall

Rotrua Farms – Base Scenario
rotrua farm

2.0 Overseer N Leach Variance for Soil Type Rainfall & Crop
Rotorua Farms – Base Scenario

rf scenario1

Rotorua Farms – Base No N Scenario

rf scenario2

3.0 Fodder Crop Yield Influence on N Leach Result

rotrua farm

4.0 Test for N Leached with Variable Clover Content of Pasture

test for ntest for n charttest for n 1test for n chart 1test for n 2test for n chart 2


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