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How Does Yield Prophet Work?

Simulation Inputs
 

The crop simulations are created by combining the essential components of growing a crop including

Soil Test Sampling

In late summer and autumn, subscribers sample the soil in their Yield Prophet paddocks down to the maximum rooting depth of their crop at different intervals (eg 0-10, 10-40, 40-70, 70-100cm). These samples are analysed for water content, organic carbon, nitrate and chloride concentration, electrical conductivity and pH. This information is entered into the Yield Prophet web interface and is then used by the grower/consultant and the Yield Prophet team to select a suitable soil classification. Information on the requirements and costs of initial soil data are available on the 2012 Soil Sampling Information page.

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Soil Classification

An appropriately measured soil classification is essential for Yield Prophet to accurately simulate crop growth and yield.

The Plant Available Water Capacity (PAWC) and bulk density of a specific soil type are used to determine how much of the measured water and nitrogen is available to the crop for growth during the season. PAWC is determined by a soil’s ‘Drained UpperLlimit’ (DUL, or field capacity) and its ‘Crop Lower Limit’ (CLL, similar to permanent wilting point).

Yield Prophet has a catalogue of soil classifications for many of the major cropping soil types found throughout Australia.  More information about the catalogue of soils can be found on the APSOIL website.  Many subscribers have soil types for which there is no available measured classification data. In these circumstances, a soil classification is estimated based on soil type and previous rainfall and crop yields, and any information available from existing soil surveys. An estimated classification is less likely to produce accurate results in comparison with a measured classification and it is recommended that potential subscribers to Yield Prophet consider characterising their soil if no appropriate data exists.

If you are interested in having your soils characterised or would like more information please feel free to contact Tim McClelland. Alternatively, if you would like to understand more about soil classification process, please visit the APSOIL website for a methodology.

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Climate Data

Yield Prophet uses entire climate record, ~120 years of data (maximum and minimum temperature, radiation, evaporation and vapour pressure) taken from the subscriber-nominated BOM weather station to simulate crop growth and make predictions about crop yield. The climate information is sourced directly over the web from the SILO Patched Point Dataset (PPD). This is a catalogue of climate information for 4600 weather stations across Australia. If you wish to know more about the SILO PPD please visit the SILO website.

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Rainfall Data

During the season, Yield Prophet subscribers may enter rainfall for each paddock into the web interface. Alternatively, they can opt to utilise the seasonal rainfall data recorded at their nominated BOM station.

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Crop Details

Yield Prophet requires subscribers to enter individual crop details into the website for inclusion in the simulations. Specific details required are the type and amount of starting stubble, sowing date, crop type, cultivar and sowing density.

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Fertiliser and Irrigation Applications

During the season, subscribers update paddock management details (cultivations and nitrogen fertiliser and irrigation applications) as they occur.

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Crop Growth Simulation

When a report is requested, the paddock-specific information is emailed from the Yield Prophet database to a computer cluster where the simulation is processed. Using climate data for the current season, Yield Prophet simulates the soil water and nitrogen processes in the paddock from the soil sampling date together with the crop growth from the user-nominated sowing date, up to the present. Yield Prophet calculates the amount of water and nitrogen available to the crop and the water and nitrogen demands of the crop. This is used to determine whether the crop is suffering stress from lack of either of these resources and any resultant reduction in growth and yield potential.

Using historic climate data, Yield Prophet then simulates crop growth and resource availability from the day on which the report was generated to the end of the season.

This process is repeated once for each year of climate record (~120 years) providing 120 separate yield outcomes (Figure 1). These yields are then plotted as a probability curve (Figure 2), providing growers with an estimate of the probabilities of obtaining a range of yields. This output is then adapted to the requested report type and emailed to the database where it can be viewed by the subscriber. Report generation takes from five to fifteen minutes.

 

  Figure 1 (above): Visual representation of the Yield Prophet simulation process

 

Figure 2 (below): is the main output of Yield Prophet which is a core component of all the reports generated in Yield Prophet.  Figure 2 is showing that this crop has:

Figure 2 (above): A yield probability curve, the principal output of yield prophet.

 

Scenario predictions

The likely impact of different sowing dates, varieties and irrigation and nitrogen applications can be determined by simulating different ‘scenarios’. Yield Prophet generates a probability curve for each scenario, and subscribers use this to determine the probability of achieving a yield response from the addition of water or nitrogen (Figure 3 and Figure 4), or from different sowing dates and varieties (Figure 5). Yield Prophet can also calculate a nitrogen gross margin based on the predicted grain quality and price (Figure 6).

Figure 3 (above): Yield probability curves for three different nitrogen top-dressing scenarios generated for a dryland wheat crop. Scenario 1 (pink line) is the yield probability adding no further nitrogen, Scenario 2 (blue line) is the yield probability with 20 kg/ha of nitrogen top-dressed and Scenario 3 is the yield probability with 40 kg/ha of nitrogen top-dressed. There is an 80% chance of achieving a yield response with top-dressing, and about a 30% chance of achieving a 1 t/ha yield response from 40 kg/ha of nitrogen.

Figure 4 (above): Yield probability curves for three different nitrogen and irrigation scenarios generated for an irrigated wheat crop. Scenario 1 (pink line) is the yield probability adding no further water or nitrogen, Scenario 2 (blue line) is the yield probability with an additional 50 kg/ha of nitrogen top-dressed, Scenario 3 is the yield probability with 50 kg/ha of nitrogen top-dressed and two additional 25 mm irrigations.

Figure 5 (above): Yield probability curves for three different sowing date scenarios (sowing dates are shown above the graph) generated for a wheat crop at Birchip.

Figure 6: Nitrogen profit curves for the same nitrogen application scenarios shown in Figure 3. Each line is calculated as the return from grain (determined by yield and protein minus cost of fertiliser and spreading) for Scenario 1 (solid pink line 0kg/ha of nitrogen) Scenario 2 (solid blue line, 20 kg/ha of nitrogen) and Senario 3 (solid red line, 40 kg/ha of nitrogen). This shows the difference in return between applying nitrogen of specified amounts, and not applying nitrogen. In this case, the cost of fertiliser is assumed to be $2.00 per kg of nitrogen, cost of spreading $10 per ha and the wheat price (AH) $350/t, with a $2.50 per 0.5% protein bonus.

How much does it cost?


There are three costs associated with subscribing to Yield Prophet®: a subscription fee, soil sampling expenses and soil analysis charges.  The total cost of subscription usually ranges between $250 and $400/paddock (ex GST).A breakdown of these costs is shown below:

Yield Prophet subscription

See it for yourself


You can visit the Yield Prophet website (www.yieldprophet.com.au) to view previously generated reports for the BCG trial site and access help files with more information about operating Yield Prophet and how to interpret reports. Simply respond to Username and Password by typing in ‘Visitor’.

For further information...

Please contact:   

Tim McClelland
Yield Prophet Coordinator
p: 03 54 922 787
f: 03 54 922 753
m: 0400 090 659
e: yieldprophet@bcg.org.au

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