What is Yield Prophet?

Yield Prophet® is a web interface for the crop production model APSIM (http://www.apsim.info/). It simulates crop growth based on paddock-specific inputs of soil type, pre-sowing soil water and nitrogen, rainfall, irrigation and nitrogen fertiliser applications, and climate data.

Yield Prophet was developed by BCG (Birchip Cropping Group) in collaboration with CSIRO as a risk management tool for dryland farming systems in the Victorian Wimmera and Mallee, with an emphasis on decision support for nitrogen fertiliser inputs. It was first used for wheat at BCG trial sites in 2002, and its early predictions of the failure of that season generated sufficient interest and credibility to allow a commercial release to BCG members in 2003 as a monthly fax-out service. Continuing demand resulted in the development of the Yield Prophet web-interface, which allowed a larger number of subscribers to receive up-to-date crop information and forecasts in 2004.

2005 was the first year of general commercial release of the service, and 338 paddocks were subscribed to the service from all over Australia and over 6800 reports were generated during the season. Subscriptions grew in 2006 to include 540 paddocks, and over 9000 simulations were generated.

Subscriptions for 2007 are now open!  For details on how to subscribe to Yield Prophet in 2007 click here. 

How does Yield Prophet® work?


Farmers or consultants subscribe to the service in late summer and autumn and provide the Yield Prophet team with their paddock names, locations (used to determine soil type and closest Bureau of Meteorology weather stations) and planned crops and varieties.

Subscribers are then given a user name and password allowing them to log onto the Yield Prophet website. Growers are also able to nominate a consultant with whom they wish to access Yield Prophet, and this consultant is also given access to data on that grower’s paddocks.

Soil sampling

During autumn, subscribers sample their Yield Prophet paddocks’ soil at different depth intervals down to the maximum rooting depth of their crop (e.g. 0-10, 10-40, 40-70, 70-100 cm). These samples are analysed for water content, nitrate concentration, organic carbon, electrical conductivity, chloride concentration and pH. These data are entered by growers into the Yield Prophet web interface, and are also used by the grower and Yield Prophet team to select a suitable soil characterisation.

Soil characterisation

An appropriately measured soil characterisation is an essential input for Yield Prophet to simulate crop growth, yield and protein accurately.

The plant available water capacity (PAWC) and bulk density of a specific soil type 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).

The Yield Prophet team have a ‘library’ of soil characterisations measured for many of the major cropping soil types found throughout Australia. However, many subscribers have soil types for which there are no available measured characterisation data. In these circumstances, a soil characterisation is estimated by the Yield Prophet team based on soil type and previous rainfall and crop yields provided by the growers, and any information available from existing soil surveys. An estimated characterisation is less likely to produce accurate results in comparison to a measured characterisation, and it is recommended that potential subscribers to Yield Prophet consider characterising their soil if no appropriate data exist. For more information, please contact Neal Dalgliesh on 07 46881376, mobile 0427 725955 or e-mail.

Crop growth simulation

During the season, subscribers enter paddock management details (sowing date, crop type, variety, nitrogen fertiliser and irrigation) and rainfall.  When growers wish to find out how much water and nitrogen is currently available to a crop, the likely yield of their crop, or what the likely impact of management events will be, they generate a report.

When a report is generated, Yield Prophet simulates daily crop growth from sowing up to the present using the paddock specific rainfall and management data entered by the subscriber, and climate data (maximum and minimum temperature, radiation, evaporation and vapour pressure) from the nominated BOM weather station.

At every daily time step 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. This information is then presented to subscribers in reports returned to the subscribers’ account (Figure 1).

Yield prediction

In order to make predictions about crop yield, Yield Prophet uses the last one hundred years of climate data taken from the nearest Bureau of Meteorology weather station to continue the simulation from the date of report generation to the end of the season. The model simulates one hundred different crop yields and proteins, based on the current season up until the day the report is generated, and on the season finishes of the past one hundred years. These yields are then plotted as a probability curve (Figure 2), which provides growers with an estimate of the probabilities of obtaining different yields. This range of probabilities narrows as the season progresses and components of yield become more certain.

This is the main output of Yield Prophet, and its value is increased by incorporating seasonal forecasts, such as the Southern Oscillation Index (SOI) phase system. In this case, instead of using season finishes for the last one hundred years, Yield Prophet selects the years in which the SOI phase was the same as in the current year, and runs the future part of the simulation using only the finishes from those years. This creates another probability curve which growers can use if the SOI phase is strongly indicating wet or dry conditions (Figure 3).

Figure 3. Yield probability curve generated using season finishes for the last hundred years of climate data (solid blue line), and only those years in which the SOI phase was the same as the current phase at the time the report was generated. In the above example, this is the years with a negative SOI phase in July-August; the report was generated for a paddock near Birchip on 1 September 2006.

Scenario predictions

The likely impact of different sowing dates, varieties and irrigation and nitrogen applications can then 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 or protein response from the addition or water or nitrogen (Figures 4 and 5), or from different sowing dates and varieties (Figure 6). Yield Prophet can also calculate a nitrogen gross margin based on likely grain quality and price (Figure 7).

Yield Prophet® in 2007

New features available in Yield Prophet in 2007 will include:

• Climate change report
• Irrigation water gross margin
• Frost and heat shock risk at flowering
• Crop biomass at flowering (to support hay cutting decisions)
• Effect of stubble management on soil water

See it for yourself!

You can visit the Yield Prophet website to view previously generated reports for the BCG trial site and access help files which will tell you more about operating Yield Prophet and how to interpret reports. Simply respond to Username and Password by typing in Visitor.

Pricing & Subscription

For Yield Prophet subscription types and prices click here. Prices do not include sampling and analysis for initial soil conditions. Information on the requirements and costs of initial soil data are available here.

To subscribe to Yield Prophet in 2007, register online. Please register before 1 April to ensure access prior to sowing.

For further information...

Please contact:

James Hunt - Yield Prophet Coordinator, BCG
Phone: 03 9354 1654
Mobile: 0429 922 787
Email: james.hunt@aanet.com.au

A one-page flyer for Yield Prophet is available.

Reports on national accuracy for past years are available – 2004  2005  2006

The Yield Prophet Project is supported by the Australian Government through the Information Technology Online (ITOL) Program of DCITA (Department of Communications, Information Technology and the Arts).  

Yield Prophet is also partially funded by the GRDC supported Land and Water Australia MCVP (Managing Climate Variability R&D Program) project: 'Prophetable' Cropping Using Seasonal Forecasting Tools.