The Scientific Method for 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 problems §Methodological: 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 plant §Pattern of plant w/problem in the field §What 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 l 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 literature §Extension bulletins §Peer-reviewed articles §Talk to other gardeners or farmers in your area §And 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 Bulletin

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) observation §Needs to be able to be tested by an experiment §Observation Yellowing and death at crown (where stem meets the soil) is due to damping off testable experiment

Hypothesis §The 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 tissue §Reinoculate (apply fungi to) peas under sterile damp soil conditions §Observe symptoms-- are they the same? §Re-isolate the same fungus complex §This 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 experiment 1) Treatment group l Pea plants are inoculated using agar with fungus complex 2) Control group l ONLY difference between the two is only the ONE variable you wish to test l For example if you have the fungi on agar blocks and you are using the blocks for inoculation then your control is ….

3) Repetitions §Why are repetitions needed? l Do all plants with symptoms have the pathogen l Does the fungus or pathogen complex cause the disease l Environment: Does damping off arise only in damp spots §How many times do I need to repeat experiment? l Depends on variability in system

Pea with Pythium root rot vs. control

Pea damping off and root rot due to Pythium

A further hypothesis You 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” l 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 l 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 l Hypothesis-- Smooth peas on the market have a greater tolerance to damping off. l 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.” l Predictive l May be modified with new information l “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” uc.edu.