The Scientific Methodfor Solving Problems

Martha Rosemeyer

Eco Ag/Organic Seed

April 1, 2004

Outline

I. Observe your situation

II. Gather data from literature

III. Develop a testable hypothesis

IV. Test your hypothesis

V. Analyze data and determine whether

supports hypothesis or not

Why the scientific method?Useful for solving certain types of problemsMethodological: Françesco Redi and Louis

Pasteur used the scientific method to disprove the widely-held idea of “spontaneous generation” (that life arises from nothing)

Technological: In 1600’s the invention of microscope permitted viewing of germ cells

I. Observation is key

Look at problem- invest in a hand lens for insect and disease problems

Pattern of plant problem on the plantPattern of plant w/problem in the fieldWhat are the possible causes?What can we test for?

Example

You are watching pea seedlings come up in certain areas of field come up yellow

Observe the plant closely

Dark brown collar near soil line (crown) of plant

Plant can fall over Photo is of soybean

damping off

Observe the pattern in the field

You notice that low spots in the field have the symptom

Low spots collect water remain damp

II. Check the literatureExtension bulletinsPeer-reviewed articlesTalk to other gardeners or farmers in your

areaAnd to return to an example, Darwin not only

observed and took notes during his voyage, but he also studied breeding and read the works of other naturalists to form his Theory of Evolution.

WSU Extension BulletinDamping off and seed rot of peaSoil-borne fungus complex

Seedlings may be infected and fail to emerge from thesoil. Emerged seedlings are also attacked, causing them towilt and topple over. Water-soaked or brown to blacklesions are often visible on the stem at the soil line. Plantsbecome more resistant to attack as they mature. Damping-off fungi are more of a problem in cold soils with poordrainage, and in conjunction with overwatering.

WSU bulletin:Cultural control of damping off

Do not overwater!Do not plant in soils known to be infested with

damping-off fungi. Mulch to help raise soil temperature. Plant in warm, well-drained soils during warm, dry

weather (when possible). Plant shallowly to encourage quick seedling

emergence and growth.

--WSU publication

III. Formulate a hypothesis

Hypothesis is a statement that has two parts: Need a) testable explanation for the b)

observationNeeds to be able to be tested by an

experimentObservation Yellowing and death at crown

(where stem meets the soil) is due to damping off testable experiment

HypothesisThe observed symptoms (lesions at soil line,

yellowing) are due to damping off caused by a complex of fungi (Pythium sp., Rhizoctonia solani and Fusarium sp.).

What you observe is the effect and the hypothesis is the potential cause

Multiple hypotheses should be proposed wherever possible, e.g. “The observed symptoms are due to Aphanomyces root rot or an insect.”

IV. Test the hypothesis

Isolate the fungi from the diseased tissueReinoculate (apply fungi to) peas under

sterile damp soil conditions Observe symptoms-- are they the same?Re-isolate the same fungus complexThis process ascribing causality of the

pathogen with the symptoms is called “Koch’s postulates”

• Broth experiment to disprove spontaneous generation

– broth in open flash (control treatment)

– broth in closed, sterile flask (experimental treatment)

• Data demonstrated that spoiled broth an microbes were present in open flask only in repeated tests (repetitions)

• Therefore microbes did not arise by spontaneous generation

• Conclusion(s): Organisms do not arise by spontaneous generation in this manner. To quote,

– “Life is a germ, and a germ is Life. Never will the doctrine of spontaneous generation recover from the mortal blow of this simple experiment.”

--Louis Pasteur

Three essential ingredients of a scientific experiment1) Treatment group

Pea plants are inoculated using agar with fungus complex

2) Control group ONLY difference between the two is only the

ONE variable you wish to test For example if you have the fungi on agar blocks

and you are using the blocks for inoculation then your control is ….

3) RepetitionsWhy are repetitions needed?

Do all plants with symptoms have the pathogen Does the fungus or pathogen complex cause the

disease Environment: Does damping off arise only in damp

spots

How many times do I need to repeat experiment? Depends on variability in system

Pea with Pythium root rot vs. control

Pea damping off and root rot due to Pythium

A further hypothesisYou read in the literature and notice in

previous plantings that a number of varieties of pea (in a variety trial) that smooth-seeded varieties have greater problems with damping off than wrinkled. You set out to test some new smooth and wrinkled pea varieties, as we will.

What is your hypothesis?How would you test this?Treatment, control, how many reps?

V. Determine if the results support the hypothesis

Hypotheses can be proven wrong/incorrect, but can never be proven or confirmed with absolute certainty. They are “supported by the experimental results” Impossible to test all given conditions, and

someone in the future may find a condition under which the hypothesis does not hold true

Research is cumulative and progressive. Scientists build on the work of previous researchers, and one important part of any good research is to first do a literature review to find out what previous research has already been done in the field. Science is a process — new things are being discovered and old, long-held theories are modified or replaced with better ones as more data/knowledge is accumulated.

That’s nice but how can I make my results predictive?Another way to say this is “generalizable”This is where the compost tea experiment

last quarter suffered-- not predictive the worm bin compost (valid unto itself) and

other compost were only one example, but this was a preliminary experiment

How to make the predictive case

More tests ie more round vs. wrinkled seeds inoculated and under damp conditions Hypothesis-- Smooth peas on the market have a

greater tolerance to damping off. Has a predictive or generalizable result

ultimately

A theory...“..is a generalization based on many observations

and experiments; a well-tested, verified hypothesis that fits existing data and explains how processes or events are thought to occur.” Predictive May be modified with new information “Theory” in colloquial language means something not

solidified, but it is much more tested than hypotheses!

The role of serendipity or a positive, unexpected result Sometimes serendipity (Serendib = former

name for Ceylon) happens“Chance favors the prepared”Important to be an observer, especially

where your data doesn’t fit your hypothesis!

Scientific method for round vs. wrinkled peas and damping off

I. Observe your situation

II. Gather data from literature

III. Develop a testable hypothesis

IV. Test your hypothesis: treatments, control,

repetitions

V. Analyze data and determine whether

results support hypothesis or not

References

“The Scientific Method” cjcarter @ uc.edu.