Assignment1
Trimester2,2013
Report1

Aim:- The aim of this assignment is to expose you to decision support models, and to
developan understanding of N and water in farming systems. Information on water use
efficiencyis discussed in Topic 7, and nitrogen budgeting is discussed in Section 6.4.4,
with additional information being included on Moodle, in the additional reading in the
physiologysection, and in the manual “Managing Legume and Fertiliser N for Northern
Grain Cropping”.

This assignment will require you to investigate the nutrient and water requirements, and
crop physiology, of a wheat paddock over the next 8 weeks.
YieldProphet

Yield Prophet® is an on-line crop production model designed to present grain growers
and consultants with real-time information about their crops, providing integrated
production risk advice and monitoring relevant to farm management. Yield Prophet
operates as a web interface for the Agricultural Production Systems Simulator (APSIM),
and generates crop simulations and reports to assist in decision making. By matching
crop inputs with potential yield in a given season, Yield Prophet subscribers may avoid
over- or under- investing in their crop.

The simulations provide a framework for growers and advisors to:
•?Forecast yield
•?Manage climate and soil water risk
•?Make informed decisions about nitrogen and irrigation applications
•?Match inputs with the yield potential of their crop
•Assess the effect of changed sowing dates or varieties
•?Assess the possible effects of climate change
Assignmentsetup:-

Go tohttp://www.yieldprophet.com.auand login to Yield Prophet using the user name:
UNEStudent21and password: une

Select a region/paddock to monitor. You have a choice of Boggabilla
The actual weather and soil information for this year has been entered for these sites, and
thiswill be suitable to start this assignment. However, if you want to change details to
better reflect your local area or paddock, then you can modify the following:
•?the paddock location and weather station used (select information to do this)
•?the variety sown, sowing date, and population (select crop)
•?soil type
•?N and water values, rooting depth, and stubble cover and type for your soil
•?applications of N, water, etc. You will be expected to modify both N and waterduring the assignment.

There will be an information file on Moodle which explains how to do each of these.

Answeringquestions:For most of the questions, there is no completely right or wrong
answer. What we want you to do is show us that you understand what is driving the
system, or causing the differences/trends which you are seeing, and how these
interactions between weather, soils, nutrients, and crop are important in managing a
farmingsystem.

When you are showing us that you understand, please keep your answers short – a couple
oflines to a paragraph is all we are expecting for most points in a question. This saves
time for you when answering, and for us when marking.

Include the relevant graphs from the reports – this will help your answer, and allows us to
seethe information you are basing your answers on.

Reportpart1
20/25marks

Generateacropreportforyourpaddock(SelectReports>Create>CropReport)

1. What is your estimate of the yield of this crop? Base your comments on the
climate forecast, and yield probability curves, and comment on the range of
predicted values.
Discuss the range of yields predicted with current nitrogen application, and when
N is unlimited from now, and from the start of the season. Your comments should
includethe differences between wetter and drier years for the different N scenarios.
Comment on whether yield has been lost up to this point from the lack of nitrogen.
2. Give your thoughts or comments on the following from the crop report
a. The amount of rainfall which has fallen so far, in comparison to historical
records.
b. Crop rooting depth (now and the final limit),
c. water and N availability and stress,
d. likelihood of frost and heat stress affecting this crop.
e. You are planning to spray fungicide to protect the flag leaf just after it has
emerged – when are you likely to be spraying.
To get more information on heat and frost risk, you can use the sowing
opportunityreport on Yield Prophet, or the CropMatewebsite
(http://cropmate.agriculture.nsw.gov.au but not for WA sites) to calculate
when the window with the lowest risk of heat or frost stress is.

3. Using the Nitrogen Comparison Report (and possibly the N Profit Report), apply
different rates of N to determine what you think is the optimum rate of N for this
site(you don’t need to include these reports in your assignment). Then apply that
rate of N at different timings to see whether timing is important in your region. I
would suggest the following three timings to start with, but feel free to play with
others if you want.
a. Presowingor at sowing
b. Growth stage GS16 (6 leaf stage late tillering)
c. Growth stage GS37 (flag leaf emergence)
Briefly discuss the results, including why there are differences between timings.
You should also include comments on which of these timings (or other timing)
you would use, and how other factors, such the initial N level, might influence
yourdecisions.

Tips

•?Use the crop report to determine the dates these growth stages occur.
•?Assume the following when using the N profit report – grade APW, 10.5% protein,
protein payment $5/%, grain price $250/t, nitrogen price $1.50/kg
•If your paddock has high levels of N applied at or before sowing, and is
not responsive to these applications, remove this initial application and
apply it at the above growth stages to see if you can improve on your
existing strategy. Write a comment so that we can see what you have done.
4. This question is looking at the effect of starting soil water levels on yield. Pick
one of the other sites, and modify it to have the same weather station and soil type
as your existing scenario. Set up the initial soil water levels to be different to your
existing scenario.

For Boggabilla, start with approximately 15-25% of a full profile.The actual
percentage isn’t important, it’s the difference between wet and dry profiles we are
interested in. See the ‘Modifying the setup in YP’ file on Moodle for how to
change water if you don’t see what you should be doing.

Produce a crop report, and discuss the differences in yield between this scenario
and the results from the initial soil water level (Q1). Include comments on the
differences between the current and unlimited N yields, and between wetter and
drier years.

5. Using the Irrigation comparison report and the best rate and timing of N from Q3,
enter the following scenarios to add water to the crop (this could be rainfall or irrigation):
a. Pre-sowing 100mm, 75% efficiency
b. GS16 100mm, 75% efficiency
c. GS65 100mm, 75% efficiency
Discuss the effect of increased rainfall/water on yield, and particularly the
differences in response between the different growth stages.

Report part 2:5/25 marks

This follow up is to observe how the yield predictions have changed over time in
response to rainfall, and to look briefly at how much and when the crop has been stressed.
Ideally this would be done after grain fill or at harvest, but the trimester is a little too
short for this.
For your initial scenario/soil set up with your recommended N rates from Q3.
6. What are the yield estimates for this crop now? Comment on what has influenced
the yield estimate, and include comments on what has stressed the crop, and when
this has happened.
7. Review your nitrogen rate decision from Questions 3 – is this rate still a profitable
decision, given the rainfall which has occurred? If you had made this
recommendation to a grower, what would you be saying if they were attacking
your decision (if it is still a good decision, well done, but outline your response
had it been a very dry finish, or very wet finish).