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Biometrical exercise 2

This material addresses aspects of the following syllabus outcome:

H4.1 applies appropriate experimental techniques, technologies, research by methods and data presentation and analysis in relation to agricultural problems and situations.

The work presented in the following section contributes towards achieving the following syllabus content areas:

experimental analysis and research in plant/animal systems
the role of a control, randomisation, replication and standardisation of conditions
the collection and analysis of data.

Source: NSW Board of Studies Agriculture Syllabus

In this biometrical exercise you will examine the results of a field trial, measuring the effect of preplant urea on the yield and protein levels of wheat.

After you have read the aim, method and results of the growth trial, you should answer the questions.

Aim: To determine the effect of preplant urea on the yield and protein levels of wheat.

Method: The trial was carried out on the same property. Each replication was carried out in paddocks with similar aspect and soil type.

All areas used in the trial had had the following treatments:

prior to the wheat sowing, canola had been grown
in February the canola regrowth had been removed
in April the areas had been sprayed with 'Logran' to control ryegrass and canola regrowth
the wheat crop was sown in May to a depth of 20 cm and at a row spacing of 17.5 cm
the seeding rate was 65 kg/ha
100 kg/ha of DAP was added with seed.

There were three treatment groups:

treatment A received preplant urea at 60 kg/ha
treatment B received preplant urea at 120 kg/ha
treatment C received preplant urea at 180 kg/ha.

The preplant urea was added to each area, one week prior to sowing.

Three different areas were used for the trial. The layout and yields obtained from each treatment and replicate are shown below.

C 147.7 kg	Control 107.5 kg	A 110 kg	Control 102.5 kg	B 109.3 kg
A 110.5 kg	Control 95 kg	B 147.5 kg	Control 99 kg	C 155 kg
B 117.5 kg	Control 109.5 kg	C 138.9 kg	Control 103.8 kg	A 114.5 kg

Each treatment plot was harvested individually with a conventional harvester.

Results: The yields for each treatment plot are shown on the layout. The results of the protein percentages for each treatment were not determined.

Means and Standard deviations for Control, Treatments A, B and C.

	Control	Treatment A	Treatment B	Treatment C
Mean
Standard deviation	5.35	2.46	20.11	8.06

Questions:

Explain why it was necessary to ensure that all areas of land used for the trial has been treated in exactly the same manner prior to the trial.
Explain why all areas of land used for the trial received identical treatment with the exception of the quantities of urea applied.
What plant nutrient(s) are supplied by urea?
Construct a table and arrange the results in a meaningful way.
Calculate means for each of the treatments and place them in the table constructed for them with the standard deviations.
Do you think that it would be a reasonable assumption to expect that increasing the quantity of urea would increase the protein percentage of the wheat? Explain your answer.
Suggest some reasons for the use of the control and why controls were positioned as they were in the trial.
Why were each of the treatments replicated three times?
The standard deviation has been calculated for each of the treatments and is shown in the table above. Explain why the standard deviation is a useful statistic.
What evidence do you have that indicates that preplant application of urea affects the yields of wheat?
What other information may be useful to decide whether it is viable economically to apply greater quantities of urea as a preplant fertilizer?
What recommendations would you make for further investigation into the effect of preplant application of urea on the yield and protein percentage of wheat?

Answers