SA - Burdekin WQIP Cane Implementation Plan Irrigation_FINAL 080319 (1) | Page 48

As shown in Table 5.1 , three paddock models , the Agricultural Production Systems sIMulator ( APSIM ), GRASP and HowLeaky are used to generate constituent loads in sugarcane . For irrigation management , it is important to note that the modelling does not model an irrigation system as such ( e . g . furrow , drip , overhead low pressure ) but rather the amount of water applied and how often . Scenarios are created that mimic typical management situations seen in the field .

Table 5.1 . Paddock modelling approaches used for each constituent in sugarcane in the Paddock to Reef program .

Constituent Paddock modelling approach

Phosphorus Particulate P Function of hillslope erosion and soil TP ( in Source )

FRP and DOP Pesticides

HowLeaky functions on APSIM water balance HowLeaky functions implemented in APSIM

5.1 Model assumptions

The paddock modelling team from DNRME are currently updating the model parameterisation for sugarcane in the Lower Burdekin . A workshop was held in June 2018 with a small expert working group to review the various management specifications and combinations to be modelled , which for many parameters , varies between the BRIA and the Delta . The parameters include the dates for a crop cycle , cover management , tillage , irrigation , recycle pits , nitrogen rates and timing , mill mud and pesticide products and timing . The current model specifications for some of the parameters that were adjusted in the update are provided below . Further detail , such as the final definition of the local crop cycles , is available directly from the DNRME modellers .

Nitrogen rates and timing

Nitrogen use efficiency – The modellers are proposing to set N rates according to the rules in Table 5.2 . Note that the modellers will implement rules for min / max rates in each category to ensure that there is no overlap between management categories with fixed rates ( e . g . Cp ) and categories with NUE rule based N rate calculations ( e . g Df ).

Table 5.2 . Nitrogen rates used in the paddock modelling for the P2R Water Quality Risk Framework . NUE = Nitrogen Use Efficiency ; 6ES = Six Easy Steps ; DYP = District Yield Potential .

ABCD / WQ Risk

Af Lowest

Bf Low- Mod

P2R WQ Risk framework Strategy **

Six Easy Steps Nutrient Management program is employed , which includes yield monitoring and use of the results from leaf testing and fertiliser strip trials .

NUE and Rate Rules Plant Ratoons Notes

6ES Management Zone Yield Potential

5 per cent lower than Bp

5 per cent lower than Bp

Assumes 30 per cent difference in yield zones Moses project results – John Hughes

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