Science Buddies: "Ask an Expert"

I've conducted my expierment, and I'm analyzing my data. The variables I am testing are the number of sprouts, height of sprouts, number of branches/stems, number of leaves, and color of the pea sprouts.

In my conclusion, I want to explain why some of my data happened the way it did.

So my question is, What does sand add to soil and how does it physically affect the plants and the soil?

By the way, I'm in 8th grade, and have been working on this project in science classes since 6th grade.

Hi!
Sounds like a really cool project. Here are a couple of links which might help-
http://www.usc.edu/CSSF/History/2006/Projects/S1619.pdf
http://www.newton.dep.anl.gov/askasci/b ... t00570.htm
Hope this helped, good luck!

Hi PeaPod,
Interesting experiment. Sand can improve the drainage of clayey soil, but a very sandy soil can have too much drainage to support certain vegetation. The exact results you'd expect to get depend on the experimental conditions. What was your procedure?
Looking forward to hearing more about your project.
Chris

Thanks Stary113!

Hi ChrisG, Could you please explain how (and anyone else could also explain please) my 5 variables are affected by the sand in the soil? Thanks so much for your time and help. I've asked this question on numerous forums and researched this 'till my brain is rot, but I still can't find what I'm looking for! Hopefully you can help

Here were my procedures:

Procedures

1. Buy all of the materials necessary.
2. Put on your garden gloves.
3. Using your silver metallic Sharpie, label each cell numbers one through nine, starting in the top left corner. Don’t forget you’ll want to be able to see the numbers once the soil is in the cells, so place the numbers in a logical way. Each of your three plant-holders should now look exactly like this:

1 2 3
4 5 6
7 8 9

4. Remove three plant labels from the package.
5. Using your thin line black Sharpie: (Once done labeling, place one of each of the plant labels in the “two” cell of each plant-holder.)
a. Label one plant label “Control – No Sand”.
b. Label one plant label “1/4 Teas.”
c. Label one plant label “1/2 Teas.”
6. Open your bag of sand with the scissors.
7. Open your bag of soil with the scissors.
8. Open your package of pea seeds with the scissors.
9. Set the plant-holders “1/4 Teas.” And “1/2 Teas.” Aside.
10. Place the plant-holder “Control – No Sand.” In front of you.
11. Heap the tablespoon full of soil. Make sure it’s heaping. Dump the soil into cell 1.
12. Place 1 pea seed onto the soil.
13. Fill the tablespoon full of soil. Scrap the excess soil off with the butter knife. Dump the soil on the rest of the soil.
14. Pat down the soil.
15. Repeat steps 7. through 12. for each cell, numbers 1 through 9. When done, all of the cells in the “Control – No Sand” plant-holder should be filled with soil and 1 pea seed.
16. Do this for every tray, except change the appropriate amount of sand per container.
17. Measure 1 cup of water into your watering can.
18. As best you can, evenly pour water into each cell of the three plant-holders.
19. Place each plant holder into the tray.
20. Place the tray in a spot that will get sunshine.
21. Every day after and including the day you planted the seeds, check to see that each cell is damp, and if not, pour a small amount of water with your watering can into that cell.
22. Every day and including the day you planted the seeds, record the data being shown. If nothing has grown yet, record this on your chart.
23. If anything out of the ordinary happens, be sure to record this on your chart.
24. If you make an error, be sure to record this as well.
25. Have fun growing your pea plants!

Hi,

I agree with Chris--the sand could either have a positive effect or a negative effect on your variables depending on what sort of soil you started with. Not only will sand change the drainage, but in such a small amount of soil it also may affect the amount of nutrients available to the plants. Also, some of your variables may be more sensitive to the effects of sand than others. I would probably expect to see more of an effect in plant height than number germinated, for example.

What were your results? It will be much easier for us to help explain what happened than it will be for us to accurately hypothesize as to what will happen.

Hi PeaPod,

This sounds like a really interesting experiment, and it's great that you've continued it for so long! As MelissaB said, it will be easier for us to help you figure out your results if you tell us what your results were.

Try asking yourself what adding sand will change for the pea plants. Based on this change, what do you think will happen to the pea plant? You can then compare your expected result with your actual result.

As an example, suppose you hypothesize that the sand does not have all the nutrients that soil does. The plants that received more sand should then have fewer nutrients in them. How do you tell if this is correct in your results? You can look at things like plant height and leaf and pod color. You would expect that the plants that receive fewer nutrients would look "sick": They should have yellow leaves and pods (or perhaps no pods), and be shorter than the control plants, since they do not have enough nutrients to grow. Then you can compare this expected result with the actual result, and see if the plants you grew with sand really are yellow and short, compared to the plants that had no sand.

Post if you have more questions,
Sonia

Here are my findings everybody... I wanted to post my graphs too, but this forum won't let me. >.<
The places at the end of the paragraphs are were I need more information. (Possible theories on why my data turned out the way it did)

How would I incorporate my research on pea plants and sand and soil into my paper, as you can see I don't have any in my paper. Also, if there are any improvements that you guys would suggest, PLEASE tell me.

This is helping me so much!

If you want to see my graphs I'll give you guys my email.

Thanks, PeaPod

Analysis and Conclusion

My research project observed the effect of the amounts of sand (1/4 teaspoon, ½ teaspoon, and 1 teaspoon) a pea plant is potted in on the number of sprouts, height of sprouts, number of branches/stems, number of leaves, and color of the pea sprouts. I found that the sand affects the color distribution of the plants and the number of the plants that sprout the most, while sand does not greatly affect the height or the number of branches/stems and leaves of the plants. Sand affects soil by making it lighter, it adds alkaline, provides good drainage, and when there is good drainage, it washes away the nutrients. It is also important to note that sand does not add nutrients to soil; it is a pure inorganic matter, called silica.

The first variable that I observed was the number of sprouts that grew in the different amounts of sand. Three out of nine plants grew in the control (no sand) pod. Five out of nine plants grew in the ¼ teaspoon pod. Two out of nine plants grew in the ½ teaspoon pod. And only one lonely plant grew in the 1 teaspoon pod. My hypothesis was, “If I grow pea plants with different amounts of sand in the soil, then the control plants with only soil, no sand, will grow the most, because the roots will be able to stretch out the farthest without the obstruction of sand.” I reject my hypothesis because 55.56% of the pea plants grew in the ¼ teaspoon pod, exceeding the 33.33% of the pea plants that grew in the control pod. Possible theory’s for why some of the plants didn’t sprout is

The second variable that I observed was the height of the pea sprouts. The control plants with no sand mixed in with the soil grew an average of 8.3 centimeters high. The plants with ¼ teaspoon of sand mixed in with the soil grew an average of 7.22 centimeters high. The plants with ½ teaspoon of sand mixed in with the soil grew an average of 8.7 centimeters high. And the plants with 1 teaspoon of sand mixed in with the soil grew an average of 7 centimeters high. My hypothesis was, “If I grow pea plants with different amounts of sand in the soil, then the plants with the most sand in the soil (1 teaspoon) will the grow the tallest, because the roots will be able to grab hold in the soil easier with the most soil.” I reject this hypothesis as well. The pea plants with ½ teaspoon of sand mixed in with the soil grew to an average height of 8.7 centimeters high, while the pea plants with 1 teaspoon of sand mixed in with the soil grew to the shortest height of 7 centimeters. It is important to note, that there was not a wide range of data collected. The range of the data is 1.7 centimeters. This is proves that sand does not significantly affect the height of pea plants. Possible reasons for this may be that
The third variable that I observed was the average branches/stems per sprout. The control with no sand mixed in the soil grew an average of 2 branches/stems per sprout. The plants with ¼ teaspoon of sand mixed in with the soil grew an average of 1.8 branches/stems per sprout. The plants with ½ teaspoon of sand mixed in with the soil grew an average of 2 branches per sprout. And the plants with 1 teaspoon of sand mixed in with the soil grew an average of 2 branches per sprout too. My hypothesis was, “If I grow pea plants with different amounts of sand in the soil, the plants with the least amount of sand (1/4 teaspoon) in the soil will grow the most branches/stems, because the plants will have a balanced amount of nutrition and water drainage (from the sand) causing the stems to grow strong.” I reject my hypothesis. All of the plants grew an average of 0.2 more branches/stems then the plants with ¼ teaspoon of sand mixed in with the soil. The range between the data is 0.2 branches. This proves that sand does not significantly affect the number of branches pea plants grow. This maybe because

The fourth variable I tested was the average number of leaves each pea plant grew. The control with no sand mixed in the soil grew an average of 7.33 leaves per sprout. The plants with ¼ teaspoon of sand mixed in with the soil grew an average of 8 leaves per sprout. The plants with ½ teaspoon of sand mixed in with the soil grew an average of 9 leaves per sprout. And the plants with 1 teaspoon of sand mixed in with the soil grew an average of 3 leaves per sprout. My hypothesis was, “If I grow pea plants with different amounts of sand in the soil, the plants with the least amount of sand (1/4 teaspoon) will grow the most leaves, because the plants will have a balanced amount of nutrition and water drainage (sand) causing the stems to grow strong, sprouting the most leaves.” I reject my hypothesis. The plants with ½ teaspoon of sand mixed in with the soil grew the most leaves, with an average of 9 leaves per sprout. Theories…

The fifth variable I tested was the color of leaves each plant grew. To test this, I created a scale: 1 means pale whitish-grey/very pale green; 2 means light green; 3 means medium green; and 4 means the optimal dark green color. Color is used often to observe how healthy plants are; and this is what I was testing. The control plants with no sand mixed in the soil were 67% light green (2) and 33% medium green (3). The plants with ¼ teaspoon of sand mixed in with the soil were 20% pale green (1), 60% medium green (3), and 20% dark green ($). The plants with ½ teaspoon of sand mixed in with the soil were 50% light green (2) and 50% medium green (3). And the plants with 1 teaspoon of sand mixed in with the soil were 100% light green (2). I concluded that the plants that were medium green (3) and dark green (4) were getting the optimal amount of nutrition; while the plants with a pale green color (1) and a light green color (2) were not getting enough nutrition, causing them to lose pigmentation. Theories…

I could have made many possible errors while conducting my experiment. Most of the errors I could have made are/were caused by human error. For example, I could have overwatered or under-watered the plants. I could have measured too much or too little sand into one of the 36 plant cells. To improve my science experiment, I would conduct the experiment in summer, not winter, and I would place the plants outside, not inside. I also would measure the water when pouring it instead of estimating. To further this experiment, I could create more variables, like the texture of the plants. Another way to further my experiment would be to send a letter to soil companies, and explain to them my findings, that way maybe the manufacturer could incorporate my data into making better soil.

Hi Peapod,

Congratulations on doing such a thorough, detailed experiment. Your procedure is excellent, I think I could do the experiment myself by reading your procedure, and that's the test of a good procedure section. I'm sorry you could not post the tables of the results, but thanks for writing out the results so we can tell what happened. You may be making your write up too difficult. You did a very carefully controlled experiment, and you measured your results, so now you just need to compare your hypothesis to your results and make your conclusions. Here are some ideas for your write up.

1. Possible theory of why some plants didn't sprout:

From your description, it sounds like you planted a total of 36 seeds, and only got only 11 plants altogether. From your procedure, it sounds like you provided the appropriate conditions for sprouting the plants, but not many of your seeds grew. It's possible that you bought a package of seeds that was old or that had not been stored properly before you got it, and so the seeds were not viable. Or, another possibility is that pea seeds are very susceptible to water mold in the soil, and they might not germinate if the mold starts growing on them first. Or, perhaps the temperature was not optimum for pea sprouting. What was the approximate temperature when you started the experiment? Here's a website that lists optimum temperature for seed germination: http://www.heirloomseeds.com/germ.pdf. Peas will sprout best between 65 and 70 degrees F (convert this to Centigrade if you include temperature in your write-up, as science fair data should always be in metric measurements, but you obviously already know this because your plant heights are in cm).

I don't think you can conclude that the differences in pea germination are related to your independent variable. And, at least you had some plants grow in all of your soil mixtures. Figuring out the exact problem that caused low seed germination would be another science fair project.

2. Height of plants: Possible reasons that the sand does not affect the height of pea plants: There is a calculation called the student t-test that can be used to determine if differences in results are significant. But you have a low number of plants in each group, so I wouldn't recommend looking this up at this point. I would just say here that the amount of sand in the soil did not appear to affect the height of the plant.

3. Number of branches: Possible reasons that sand does not affect the number of branches: Again, there are no differences in your results, so you can conclude that the amount of sand in the soil does not appear to affect the number of plant branches.

4. Number of leaves: You appear to have a difference in results here, but with only plant in the 1 tsp group, your conclusions need to be tentative. Were there any other plants in the other groups that had only 3-4 leaves? If all of the other plants in the other groups had 7-9 leaves, and there were no other individual plants that only had 3 leaves, then you can conclude that the amount of sand appears to affect the number of leaves.

5. Color of leaves: You do have a significant difference in results here. The plants with the lowest amount of sand were definitely greener than the plants growing with more sand. So you can conclude that your results show that the amount of sand is related to the green color.

In your conclusion section, you can review what plants need for optimum growth, i.e. soil, nutrients, water, light, carbon dioxide, temperature. You can review what effect adding sand would have (less nutrients, better drainage/drying out faster, alkaline pH). Then, because you kept all conditions controlled, except for the amount of sand, you can conclude that adding sand to the soil adversely affects pea plant growth because of these factors, and that number and color of leaves is the best way to measure the effect of your independent variable.

Your error section is good. You might want to add a suggestion that next time you would measure soil pH, moisture levels, and nitrogen levels at various times during the experiment. That way you might be able to measure the factors that are affecting plant growth.

I hope this helps. Let me know if you have any questions.


Donna Hardy

PeaPod,

Thanks for such a thorough writeup! You seem to be well on track. Most of what I'm going to say about things that can be changed in the writeup are minor details; you're welcome to take them or leave them, as you like.

First, about your results. You have a very low sample size. Only a few of your plants sprouted, and this makes it hard to draw conclusions. The fewer plants there are, the more likely it is that the results you are seeing are due to random chances. This is probably something that you want to mention in your errors/ future work section. Growing more plants for each treatment will give you more confidence that the results you are seeing are correct.

One thing that I notice about your data is that the control plants seem to do less well than the plants in 1/4 tsp sand: Your plants were more numerous and healthier-looking in 1/4 tsp sand than in the control. This could indicate several things: 1) The seeds were not good, and the plants in 1/4 tsp sand happened to receive more of the best seeds. Donnahardy also suggested that there might have been mold on the seeds--you could try digging the seeds back up to see if this was the case. 2) There may have been differences in conditions for the control plants, other than the lack of sand. Maybe you had the control plants set up behind the plants with 1/4 tsp sand, and the control plants didn't get enough sun, for example. Or maybe the control plants were in full sunlight, and their water evaporated quickly. Little differences like these that you noticed or remember from your setup are important to note in the errors section of your report. 3) Maybe this particular species of pea plant happens to grow best with a little sand in its soil. You could look into this by researching what its habitat in the wild is like. Does it grow in a place that might be a little sandy?

You might be able to say that the amount of sand affected the number of leaves that grew on the plants, since the average number of leaves dropped from 7 or 8 to 3 in the plants in 1 tsp sand. That's a pretty big difference! You say that you rejected your hypothesis because the plants grown in 1/2 and 1/4 tsp sand were taller than the controls; this might be because of chance, or it might be, again, that the plants grow well with some sand. But the number of leaves decreases so drastically with 1 tsp sand, it seems that there might be a cut-off point for how much sand the plants grow well in. If you put in more sand than the cut-off point, the plants no longer do as well.

The numbers for the rest of your dependent variables don't look different enough to me, given your low sample size, to say for sure that they were affected by the amount of sand in the plots. Even the color of the leaves is iffy, because 2 of your 3 control plants were light green. (Speaking of colors, it's probably fine if you talk about them qualitatively [light green, medium green] rather than with your number scale, because you distinguish between the color groups pretty clearly.)

I know you said that you couldn't post your graphs, but are you using tables to present your data as well? It might be easier for a reader to follow your conclusions if you put your data in tables. Also, because so few of your plants germinated, I would suggest using numbers or fractions instead of percentages (2 control plants were light green, or 2/3 control plants were light green, as opposed to 67% were light green). Similarly, because you only had one plant that grew in the 1 tsp plots, it's probably better to refer to it in your report as a single plant (The one plant that grew with 1 tsp of sand was light green in color).

You don't always need to worry about theories for why you got the results you did, especially where you see no effect; that's just what the data show you. I do think that it will be important to explain about the low sample size, and what this does to your experiment. Other than that, you have done a very thorough job with your experiment and your writeup. Good work!

Feel free to post again if you have more questions,
Sonia

Hi Peapod,
That's a very nice write-up. It looks like you have gotten lots of great advice here. I wanted to comment about one item:
"It is also important to note that sand does not add nutrients to soil; it is a pure inorganic matter, called silica."
To geologists, "sand" only describes the grain size of the stuff and does not indicate what minerals are present. There are sands that are predominantly quartz (SiO2), but most sand in nature is composed of many minerals. There are even beach sands that are composed mostly of magnetite (an iron oxide).

Also, for the purpose of your experiment I believe it is true to say that the sand would not add a substantial amount of nutrients that support plant growth. You might be interested to know that in natural soil systems over a long period of time, grains of minerals in sand contribute important minerals to the soil through the process of weathering.

Just some food for thought. Great work!

Chris

What would the control group be???

Hi Shaxz,

Are you asking about the control group in this "Effect of Sand on Plants" experiment? Just wondering since it's a very old thread and I want to make sure my reply makes sense!

Megan

Hello. I am in 6th grade, and I am testing a similar question for a science fair. I am testing different types of soil affecting a certain plant. The control soil is a standard store-bought soil, against sandy soil and composted soil. I have been reading these, and I just wanted to say thank you. These have helped me a lot.