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What
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Yield
Prophet® is a web interface for the crop production model APSIM (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 dry-land 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 at will in 2004. The end of season report detailing model performance
can be downloaded as a PDF.
2005
was the first year of general commercial release of the service, and 338
paddocks were subscribed to the service from all over
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 with which they can 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
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 within BCG’s membership catchment and other regions Australia-wide. 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.
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 June-July; the
report was generated in early August 2004.
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 8 and 9), or
from different sowing dates and varieties (Figure 10). Yield Prophet®
can also calculate a nitrogen gross margin based on likely grain quality and
price (Figure 11).
Figure
8.
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
9.
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
10.
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
11. Nitrogen
profit curves for the same two nitrogen application scenarios shown in Figure 8.
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
12 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
12.
The graphic display of soil water from the Irrigation Scheduling Report in Yield
Prophet®.
Yield
Prophet® in 2006
Yield
Prophet® in 2006 features many improvements on the service in 2005.
These include;
-
New
look user-friendly website
-
More
efficient website structure for consultants
-
‘Batch’
and ‘favourite’ report generation capabilities, as well as streamlined
report structures, for quicker and easier report generation
-
Long
waits for reports eliminated by installation of a 26 dual processor computer
cluster for simulation runs
-
Improved
barley module
-
User
memory meaning users don’t need to provide password during each session
-
User
selection of customised home page upon log-in
-
Automatically
updated crop growth stage readouts
- Additional agronomic information, including rooting depth and forecast timing of growth stages relevant to management (end of tillering, flag leaf emergence, flowering
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
Yield
Prophet® subscription types and prices are listed 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.
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