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2002 Trial Results - Ivan & Helen Lee |
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Saturday, 19 July 2003 |
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GRDC Precision Ag Research
Ivan and Helen Lee
Aim
To investigate the responsiveness of wheat to N, P and K on each productivity zone.
To investigate the theory that wheat crops grown on deep weak sands perform better if sown with a low seed rate. This will help to demonstrate if variable rate technology is likely to generate a profit.
Method
- The paddock was divide into high, medium and low productivity zones.
- Investigations were then undertaken to identify factors that may be limiting production in each zone.
- We investigated how varying N, P, K and seed rates would influence grain yield nd crop biomass in high, medium and low productivity zones.
Treatments
- The paddock was sown round and round, with the workings crossing the high, medium and low productivity zones. This created a donut trial design.
- The fertiliser input trial had 3 replications, and the seed rate by fertiliser demonstration was not replicated.
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Treatment |
Nitrogen kg/Ha |
Phosphate kg/Ha |
Potassium kg/Ha |
Sulphur kg/Ha |
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Low |
20 |
4 |
0 |
4 |
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Medium |
50 |
8 |
25 |
8 |
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High |
80 |
16 |
50 |
16 |
Demonstration
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Treatment |
Seed Rate |
N kg/Ha |
P kg/Ha |
P kg/Ha |
S kg/Ha |
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Low |
35 |
20 |
4 |
0 |
4 |
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Medium |
70 |
80 |
16 |
50 |
16 |
Results
- The yields of this trial were severely limited by drought (0.8-1.8T/Ha). April to October rainfall was 152mm, making 2002 a decile 1 season.
- However the crop biomass and grain yield did respond to varied levels of inputs.
Productivity zones
- The high productivity zone consistently out yielded the medium and low productivity zones, yielding 1.6T/Ha compared to 1.05T and 1.03T/Ha respectively.
Fertiliser inputs
- In the high productivity zone there was a trend for the high input plots to out yield the medium input and the medium out yielded the low input plots.
- However the yield gain was not large enough to cover the additional costs of the fertiliser inputs.
High Input Zone
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Input |
Yield Kg/ha |
Gross Income |
Income - Fertiliser cost |
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High |
1670 |
$424 |
$281 |
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Medium |
1600 |
$406 |
$337 |
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Low |
1540 |
$391 |
$367 |
On the medium and low productivity zones there was no response to altering fertiliser rates.
Seed rate by fertiliser demonstration
High Zone
On the high productivity zone, reducing seed rate from 70 to 35kg/Ha reduced grain yield by 40kg/Ha for both the high and low fertiliser treatments.
On the high productivity zone the high fertiliser treatments out yielded the low fertiliser treatments by 260kg/Ha. This generated an additional $66/Ha, however it cost an additional $119/Ha for the additional fertiliser.
Medium Zone
There were no trends in grain yield created by varying fertiliser or seed rates.
Low Zone
On the deep sands of the low productivity zone, reducing see rate to 35kg had a positive effect on grain yield (150kg/Ha).
Halving the seed rate generated a saving of $14/ha and also returned an additional $38/ha of grain.
The gross margin on deep sands was increased by $58/ha by reducing seed rates from 70 to 35kg/Ha in the dry season of 2002.
Conclusion
- The high productivity zones within the paddock gave a larger grain yield in response to increasing fertiliser inputs. However in this dry season the yield responses were not sufficient to cover the additional input costs.
- Reducing seed rates on poor performing deep sands can increase grain yield and gross return by $58/ha in a dry season.
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