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Home & Garden: Research and tomato yields

Curt Swift
CURT’S CORNER
Free Press Gardening Columnist
Close-up of a heap of tomatoes
Getty Images/Purestock | Purestock

Research means different things to different people. People often say they have researched a problem. In most cases they mean they have asked somebody a question or gone online to obtain an answer. If you are lucky, they reviewed research reported in scientific journals or talked to someone who has received specialized training or has extensive knowledge and experience in that area.

In the social sciences, research is often done using a survey. If the survey is designed properly, with an adequate number of randomly selected people responding to the survey, it can be statistically valid. Statistical validity means you will obtain the same results with the same level of confidence if you repeated the survey again with a different group of randomly selected people.

A survey to determine the feelings of the American people about President Obama using a group of Republicans who listen to and believe every word Rush Limbaugh promotes would not be considered a random selection nor would it be considered valid. A survey with a five-percent level of confidence means you should have the same results 95 percent of the time. A one-percent level of confidence means the survey when conducted in the same manner with a different group of randomly selected people would provide the same results 99 percent of the time.



With the natural sciences, the concept of research involves conducting field, greenhouse, or laboratory trials to verify the effect of a treatment. In order to have the research published, journals typically require the research to be repeated at least twice, either in different fields or at different times (even over different years). The trials are designed in such a way only the variable being examined should have an effect on the outcome.

For example, if we wanted to determine how the age of tomato seedlings effect the yield of tomatoes, we would grow the seedlings under the exact same conditions and then plant them in the garden at different ages of development. The seedlings would be grown under identical light, humidity, soil moisture, fertility levels, temperature, and other conditions to ensure all seedlings were treated exactly the same. The young tomato plants then would be planted in plots in such a manner that any difference in the garden soil would be eliminated. The only difference in yield would be age of the plants. We would then collect data from the plants (or groups of plants) and run a statistical analysis to determine if the degree of difference between the yields were statistically valid. Statistical validity means that no matter how often the trial was conducted, the results will be the same results.



The level of confidence is again critical with few research projects appearing in research journals if they exceed the five-percent level. If a trial will produce the same results only 90 percent of the time (10 percent level of confidence), getting the data published may be difficult.

To eliminate any variability in the garden soil, soil texture and structure, fertility levels, organic content, nutrient levels, soil moisture content, etc., the plants would be planted in a randomized pattern in the field or garden. Each treatment is assigned a number and where each assigned number occurs in a list of randomized numbers determines the planting pattern. There are randomized patterns as well as pseudo-random numbers and true random numbers to be considered when developing the trial. Developing a valid research trial is not easy. Conducting scientific research is not a guessing game or “fly by the seat of your pants” process.

In the case of how the age of tomato seedlings affects yield, you would want to grow the seedlings under identical conditions and transplant them into the garden at different ages. For example, if you wanted to compare the yield of tomatoes that were transplanted into the garden three, five, seven, or nine weeks of age, you would follow the procedure I’ve outlined above. You would most likely find, as previous researchers before you, tomato seedlings between five and seven weeks old when transplanted into the garden produce more fruit than older seedlings. Researchers also have found that the more frequently the seedlings are re-potted before being transplanted to their permanent spot in the garden, the lower the yield. Tomato plants with blossoms or fruit when planted into the garden also produce lower total yields.

When somebody tells you they researched a problem or topic, you might want to find out what they mean by “research.” Be inquisitive. Ask for the data. Maybe they are simply repeating hype provided by someone with an agenda.

I prefer my information to be scientifically based. When I go to the doctor, I expect him to base his problem diagnoses and treatments on science and research, not on a whim or fancy. Hopefully you feel the same way.

GJ Free Press columnist Dr. Curtis E. Swift is a retired horticulture agent with the Colorado State University Extension. Reach him at Curtis.Swift@alumni.colostate.edu, 970-778-7866 or check out his blog at http://SwiftsGardeningBlog.blogspot.com. He owns Swift Horticultural Consulting and High Altitude Lavender.


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