Organic vs Chemical Nutrients to 6 year old

[kacee]

My 6 year old son came up with the following: Hypothesis: Using organic nutrients will result in tallest and fastest growth (radish seeds using organic fertilizer and variable was liquid organic nutrients and liquid chemical (Schultz plant food). Hypothesis was incorrect, chemical results were better. He is upset that he was wrong and although I've explained what happened he says he can't understand because its too boring. Can you please tell me what I can say so he understands the results. Thank you!

[donnahardy2]

Hi,

Welcome to Science Buddies!

It sounds like your son did an excellent project and obtained measurable results. Please explain to your son that it's not possible to get a wrong answer on a science project. He did a controlled experiment and obtained results that did not happen to match his hypothesis. But that is perfectly acceptable with a science project.

The next step, if possible is to have your son think about why his hypothesis may have not matched the results. Was there a difference in the concentration of the two fertilizers? Was there any difference in the light, temperature, or water with the two groups of radishes? Was the chemical fertilizer more soluble compared to the organic fertilizer? Organic fertilizers Organic fertilizers typically have more complex ingredients that take time to break down so the nutrients are available to the plant. Can you son think of any other possibilities?

Your son is 6, so don't worry if he is not ready to go to the next step with the data analysis. Continue to be positive and encouraging. Just tell him he did a great job and his answer is correct.

I hope this helps.

Donna Hardy

[kacee]

Donna,

Thank you for the advice!

We couldn't attribute any differences (temperature, light, water, etc.) When I first asked him why he thought the organic didn't have the better results his response was "they made the chemical one to work better". I told him he was correct because the chemical nutrients dissolve immediately into the plant roots and the organic nutrients can not be taken by the the plants because they need time to break down. Can you give me examples to explain "break down".

In general I think its confusing to him because he originally got this idea when he tagged along to the farmers market and he wanted to know why I had to go to both the grocery store and the farmers market. I explained about buying organic.

In anticipation of the science fair I've asked him several questions and everything is counter intuitive because he said "organic is more expensive and therefore it must be better, but that was not the case with his results." His conclusion in his own words "he needed more time".

Explaining that we also should be tasting the radishes and looking at the quality of the roots has been difficult because I thought we should keep the plants intact to take to the fair.

Thank you for your help!

[donnahardy2]

Hi,

You have a good question. Plants absorb nitrogen in the form of ammonia or nitrate. These are very small water soluble molecules that can easily be transported across the plant cell membrane.

Here's the MSDS for Schultz plant food; it contains urea, ammonium, potassium phosphate, and potassium nitrate and trace elements. All small molecules.

http://www.schultz.com/~/media/Schultz/ ... FEB08.ashx

Organic fertilizers like blood meal, cotton meal, and manure contain proteins, which are much larger nitrogen-containing molecules. In order to use the nitrogen in organic fertilizers, the large molecules must be broken down to ammonia or nitrate by bacteria growing in the soil. This takes time, so the nitrogen is not instantly available to the plant, but it is available over a longer period of time.

Here's the MSDS for an organic fertilizer that contains fish proteins and seaweed. This is a complex source of nutrients, definitely no nitrate or ammonia.

http://www.garden.com/ContentFiles/Asso ... 40MSDS.pdf

Organic fertilizers typically contain lower concentrations of nutrients. Look at the labels on the fertilizers you purchased. The first number on the label is the nitrogen content; if the non-organic fertilizer has a higher number, then it was a more concentrated source of nutrients. If your son used the same quantity of each type of fertilizer, then he probably used less nitrogen for the organically grown radishes.

Perhaps when discussing this with your son, you could explain that the non-organic fertilizer provides nutrients faster and the organic fertilizer is slower. Is faster growing better than slow growing?

Your idea of a taste test is a good idea for a future science fair project. Organically grown foods typically taste much better than regular foods, so this is a topic that is definitely worth investigating.

Donna Hardy

[kacee]

Hi Donna,

Thanks for this detailed response, I really appreciate your time in helping me to explain this to my son.

We used a liquid organic seaweed extract and followed the directions of ratio to water and we did the same using the Schultz. I checked what it contains and yes definitely no nitrate or ammonia and the MSDS looked exactly the same as the one you sent me.

Your guidance is extremely helpful. I will let you know how it went at the Science Fair. My son will have the opportunity to speak to two scientist who will ask him questions about his project. Although, he thought this project was "boring", I think its an amazing opportunity to start thinking about what is science, making a poster board and learning through the process.

As a parent I learned what to do differently next year, including guiding him towards a project that may be more age appropriate. Also, an experiment that is not drawn out over a lengthy period of time is more appropriate for the younger age group. We did a more age appropriate project last year and it was a big hit.

Again many thanks for your time and your research.

All the best!

[donnahardy2]

Hi,

I’m glad I was able to help you with the explanation.

I think you’ve done an amazing job of encouraging your son with this project. There’s a lot of science involved and would be challenging for a much older child.

Good luck to you son at the science fair!


Donna Hardy