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 2008 are now open!  For details on how to subscribe to Yield Prophet in 2008 click here. 

How does Yield Prophet^® work?

Subscription

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).
Figure 1. Output from Yield Prophet^® indicating the amounts of water and nitrogen available to the crop during the season. The stress graphs indicate loss of potential growth and carbon fixation, i.e. on a day when the graph is at 0.5, the crop is growing and photosynthesising at half its potential rate.

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.

Figure 2. A yield probability curve, the main output from Yield Prophet.

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).

Figure 4. Yield probability curves for three different nitrogen top-dressing scenarios generated for a dry land wheat crop on 1 August 2005. Scenario 1 (pink line) is the yield probability adding no further nitrogen, Scenario 2 (blue line) is the yield probability with 35 kg/ha of nitrogen top-dressed on 15 August, Scenario 3 is the yield probability with 70 kg/ha of nitrogen top-dressed on 15 August 2005. There is an 80% chance of achieving a yield response with topdressing, and about a 50% chance of achieving a 1 t/ha yield response from 35 kg/ha of nitrogen.

Figure 5. Yield probability curves for three different nitrogen and irrigation scenarios generated for an irrigated wheat crop on 3 October 2005. 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 on 3 October, Scenario 3 is the yield probability with 50 kg/ha of nitrogen top-dressed on 3 October and two additional 25 mm irrigations on 3 and 17 October.

Figure 6. Yield probability curves for three different sowing date scenarios (sowing dates are shown above the graph) generated for a wheat at Birchip crop on 21 June 2005.

Figure 7. Nitrogen profit curves for the same two nitrogen application scenarios shown in Figure 4. Each line is calculated as the return from grain (determined by yield and protein minus cost of fertiliser and spreading) for Scenarios 2 (solid red line, 35 kg/ha of nitrogen) and 3 (solid blue line, 70 kg/ha of nitrogen) from Figure 8, minus the return from Scenario 1 (adding no further nitrogen). This shows the difference in return between applying nitrogen of specified amounts, and not applying nitrogen. In this case it assumed the cost of fertiliser as $0.95 per kg of nitrogen, cost of spreading as $5 per ha and that the wheat price would be APW at $160 per tonne, with a $2 per 0.5% protein bonus.

Irrigation scheduling

Because Yield Prophet calculates the amount of water available to a crop, and average evaporation and transpiration based on 100 years of data, it has the potential to be a very effective tool for irrigation scheduling.

Figure 8 shows the Irrigation Scheduling report from Yield Prophet. The graph shows the PAWC of the soil that is being accessed by the crop as roots grow, and the amount of PAW calculated from initial measured soil water plus rainfall and irrigation, subtract evaporation and transpiration. The red section of the line is a projection of PAW over the future two weeks assuming no rain, and growers can use this to determine when to water, and how much water to apply. The impact of any irrigation can be calculated from the probability curves in the irrigation comparison report described above (Figure 9).

This output is also very useful for dry-land crop management, as it provides an indication of the amount of water that is available to a crop at any point in the season.

Figure 8. The graphic display of soil water from the Irrigation Scheduling Report in Yield Prophet.

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