How does Yield ProphetŪ work?

Simulation inputs

Yield Prophet 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. Requirements and costs of initial soil data (new window).

Soil classification

An appropriately measured soil classification is an essential input 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 upper limit’ (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 found here (new window). 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 to a measured classification, and it is recommended that potential subscribers to Yield Prophet consider characterising their soil if no appropriate data exists.

If you would be 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, view a 36-page guide to the methodology of estimating plant available water content (PDF 2.1MB, new window).

Climate data

Yield Prophet uses the last 100 years of climate 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. Find out more about the SILO PPD (new window).

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.

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.

Fertiliser and irrigation applications

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

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, and 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 demand of the crop. This is used to determine if the crop is suffering stress from lack of either of these resources and any subsequent reduction in growth and yield potential.

Then, using historic climate data, Yield Prophet 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 100 times (once for each year of climate data) providing 100 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 different 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. Visual representation of the Yield Prophet simulation process.

Figure 2 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:

  • A yield potential of 3t/ha given the best season finish on record with available nitrogen.
  • A yield potential of 4t/ha given the best season finish on record with unlimited nitrogen.
  • A yield potential of 1t/ha given the worst season finish on record
  • A 50% chance of achieving a yield of at least 2.2t/ha with available nitrogen
  • A 50% chance of achieving a yield of at least 2.6t/ha with unlimited nitrogen
  • An 80% chance of benefitting from the application of nitrogen (i.e. the nitrogen limited curve separates from the nitrogen unlimited curve at the 80% line).

 

 

Figure 2. 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 calculates 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 likely grain quality and price (Figure 6).

 

Figure 3. 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 20kg/ha of nitrogen top-dressed and Scenario 3 is the yield probability with 40kg/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 1t/ha yield response from 40kg/ha of nitrogen.

 

 

Figure 4. 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 50kg/ha of nitrogen top-dressed, Scenario 3 is the yield probability with 50kg/ha of nitrogen top-dressed and two additional 25mm irrigations.

 

Figure 5. 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, 20kg/ha of nitrogen) and 3 (solid red line, 40kg/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/kg of nitrogen, cost of spreading $10/ha and the wheat price (AH) $350/t, with a $2.50 per 0.5% protein bonus.

Yield Prophet subscription and pricing

For Yield Prophet subscription types and prices and to register for Yield Prophet in 2010, click here (new window). Prices do not include sampling and analysis for initial soil conditions. Please register before 1 April to ensure access prior to sowing.

Read about soil testing information - requirements and costs of initial soil data (new window).

See it for yourself

Visit the Yield Prophet website (new window) 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
Phone: (03) 9882 2670
Fax: (03) 9882 0996
Mobile: (0400) 090 659
Email: yieldprophet@bcg.org.au