Hi, Team,

Thank you for letting me be a part of this. I know it was a bit frustrating at times, but I hope you learned a lot about how experiments are designed and about the trillion little things you have to think about! I was really impressed with the way you thought about setting up your experiments, and if you had more time, you would do everything over again until you felt confident in your results. You'd have a chance to answer your questions more definitively. Maybe next year :).

You did a good job talking about your experiment and your results on the poster. Your graphs showed differences between species and treatments pretty well.

Good luck with the rest of the school year. I hope you have a wonderful summer. Whatever you do, don't forget to notice the plants around you. They are pretty cool.

Take care,

Dr. P

Dr. P, 
    We would just like to say thank you for your assistance throughout this project. We greatly appreciate everything you did and the time you gave up to help us. Your insight improved our experiment and our understanding.
    Once again, thank you, 
    The Team

Hi, Team,

Thanks for the update, and I'm glad you are thinking critically about how to present your results. That's an important part of communicating science, and not everyone pays enough attention to it.

With your quantitative data (height, for example), if you want to show changes over time, you probably want to use a line graph. Line graphs are perfect for illustrating trends across time or some other ordered variable (light or water levels, for example, that would go from low to high). They also allow you to compare treatments on one figure.

But.... in your case, you have different species and different treatments, right? So you'll have to decide whether you want to make a graph for each species, with lines for each soil condition; or a graph for each soil condition that includes a line for each species. The way to decide is to figure out which result answers your main question the best. Do you want to compare species' responses to a given soil condition (=separate graph of each soil pH with species as lines) or do you want to compare growth of a species in different soils (=separate graph for each species with soil pH as lines)? We can talk more about this if you have trouble figuring that out.

Also, since you replicated (yay) and have more than one plant per treatment, you will need to plot the average height of all your plants. If you had a lot of plants per treatment (at least 10) you could do fancier statistics to show how much variation there was around the mean. You don't have enough plants to do that, but you probably still want to talk about the variation when you give your presentation. For example, there's a biological difference between an average of 5, with measurements ranging from 1 to 10, and an average of 5 with measurements ranging from 4 to 6. You could plot each plant separately, but that would make your graph very hard to read. The simplest thing would be to plot averages but make sure you write down the range somewhere and mention it.

As for the other variables, did you measure them every several days as well? Did you use some kind of number scale that could be plotted like height? Or did you use words?

For these variables, if the details of change over time are not very important, you might think about just using a table. For example you could say that blah-blah species grown in limestone soil had this color leaves and that amount of stem sturdiness by the end of the experiment. You'd put species in rows and soil conditions in columns and then just use words in the table body to describe what plants looked like at the end.

Let me know if any of this is confusing and we can talk more. Also let me know what you think and whether you agree. It's hard for me to know for sure without being there with you.

Keep up the great work!

Dr. P

Dr. P, 

The Iron Sulfate pots measured a pH of 4.8, regular soil was at pH of 6.72-6.74, and Limestone was around a pH of 6.8. Due to how quickly our plants died, we thought the Iron Sulfate soil would be lower than what it turned out to be. 

We have decided to stop our project early because of how much data we have measured; we have measured the height of the plants every several days and also noted qualitative data such as the color of different plants, how the Iron Sulfate has effected the contained, and how, for lack of a better word, sturdy, the stems are. We are all wondering if you could give us some advice on how to best format a graph or a table with our results.

Thanks, 
Team 

Hi, team,

I understand busy! Thanks for the update, though. I'm sorry that the break in watering may have complicated your results. What pH did you measure for the iron sulfate pots? Do you think you changed it too much?

Dr. P

Dr. P, 

Thank you for your patience. We have been very busy lately. 

Firstly, we planted our seeds before our Easter Break. We did end up dropping the Nasturtium. For our setup, we have four experimental groups for each plant in each of the pH level. For the peas, we put two seeds in each pot. However, for the buckwheat, we only had enough for one seed per pot.

Secondly, because no one was able to water our plants over Easter Break, most of them are not doing so well. The peas are growing best (based on our measurements) in the regular soil. The buckwheat seems to be dead or dying in most of our pots (except for one in the regular soil, which is thriving compared to the others). The iron sulfate killed all of the plants as soon as we planted them. On the iron sulfate containers, we have noticed a white substance has appeared on the sides. The iron sulfate soil has a lighter appearance than the other soils. 

Thirdly, we figured out how to calibrate the PASCO pH probes and have (what we think is) an accurate reading. They were slightly off of what we originally proposed. The limestone wasn't nearly as basic as we hoped for; it was very close to what our regular soil read. 

Lastly, we have been watering our plants consistently throughout (except Easter Break) our experiment, including the iron sulfate soil. We also have been measuring the growth of our plants' stems in centimeters every now and then. 

Thanks,

Team

Hi, Team,

Too bad you have to drop the nasturtium, but it does make sense at this point. Unless there is another species on the list that has the same pH requirements as nasturtium, you are probably best off focusing on just the two species.

I don't know for certain what might be causing differences in the probe readings, but could it be that the soil isn't adequately mixed with the limestone? Are you measuring liquid from the soil or are you measuring the soil directly? If you are sticking the probe directly into the soil and if the soil isn't uniformly wet, you could get different results. If you are putting a teaspoon of soil into water and testing the water, you might be sampling a particularly limestone-rich part of the soil in one test.

Let me know what you think of these ideas.

Good luck,

Dr. P

Hello Dr. P, 

We wanted to give you a quick update on our thoughts and progress for this week. On the 14th of March we started germinating our seeds by putting ten seeds of each type in Petri dishes (doing this three times total and having thirty seeds of each type) and adding 10 ml of water to each dish.

We were originally planning to use three types of seeds (Peas, Buckwheat, and Nasturtium); however, after leaving the seeds to germinate for six days, the Nasturtium is slow going and only has around three germinated seeds. We believe this is because of its thick outer coating, but due to its slow progress germinating and our want to start planting tomorrow, we are considering dropping Nasturtium from the experiment and only proceeding using Peas and Buckwheat. 

If we were to do this we would only need 18 pots but we would still use all three pH levels that we have been conducting tests with. While on the subject of testing pH levels, the lowest we could get the pH to was 3.8 and the highest was around 7. However, we did encounter some issues with the PASCO pH probes. We have two probes and when we were testing they didn’t seem to read the same pH levels. For example, we were testing the limestone mixed soil and one probe would read a 7 while the other probe would read around 10. We are not sure what has caused these differences and were wondering if you might have some insight into measuring pH levels and how we can be as accurate as possible. 

Thanks, 
The Team 

Hi, Team,

Your template looks great. The only thing I noticed was that your hypothesis states you will test pH of 4, but your treatment description says 3.5.

You did a great job explaining which variables you will hold constant. You are also replicating appropriately, which is essential.  One final thing to keep in mind is the location of your pots. Even if it looks like light is constant in one area, it does vary a bit. Pots right under a bulb will get more light, even if the light looks bright everywhere. Be sure to mix up your pots so that you don't have all 3 of one treatment in bright light and all 3 of another in dimmer light.

Good luck and keep me up to date!

Dr. P

Hello Dr. P, 

We have uploaded our completed design template and were just wondering if you had any feedback or further suggestions before we got started with the experiment.

Thank you, 
Andria, Meredith, and Sophie

Hi, Team,

Thanks for the update. It's better to take your time to do things right than to rush it and get ambiguous results. Keep up the good work!

Dr. P

Hello Dr. P, 

To give you an update on our progress we have updated our design template. It has been taking us longer than expected to test the different ways to change pH and get accurate readings of different soil pH levels. We used the PASCO pH probe and also tried using pH test strips. We will continue running some more tests this week to see how acidic and basic we want the pH levels to be. 

Thanks, 
Andria, Meredith, and Sophie

Dr. P,
Thank you for the ideas for the experiment, we plan on having our design done by Friday. This week we are doing more research and plan to do some preliminary testing of different factors that effect soil pH with our probes. 
Thank you, 
The Team

Hi, Team,

You are very wise to ask how to set up an experiment with so many variables. You want to test a range of pH values, but not so many that your sample gets out of control. If you were looking at just one species and you didn't know its tolerance, you might test 5 or 6 values to increase the chance of seeing a response. In your case, you have some useful information: published reports about the ranges of your test species. That background information will let you narrow your treatments.

I suspect those species tolerance ranges overlap somewhere around 6 to 6.5. Is that right? If so, then a control of sorts would be to use slightly acidic soil, which would fall in that overlapping region. All of the species should do OK there, even if it's not their optimal condition.

Assuming you can test two additional pH values, what would they be? Obviously you would test values above and below that middle point, but how far would you want to go? Think about that and we'll talk more.

By the way, the reason I suggest only three pH levels is that you would already have 3 species at 3 levels for nine combinations. You need to replicate your experiment with at least 3 pots per combination, so you are already up to 27 pots. I don't know how much room you have.

Dr. P

Dr. P,
    We have been researching the pH ranges and also how to change the soil pH. To change the pH we have some limestone available to us as well and will be conducting more research on those effects. We have also found 3 plants at our disposal, peas, buckwheat, and nasturtium, with separate ranges. We have gotten a little confused on how to set up an experiment with that many variables and were wondering if you could give us a little insight.
Thanks,
Meredith, Andria, & Sophie

Hi, team,

Thanks for your thorough answer! I'm glad you have the resources to test pH and a strong set of reasons to look at that variable.

I mentioned that some plants have a wide tolerance and others a more narrow one. Since you have many species available to you, you might think about testing more than one species. If you do a bit of research and find that two or three of your species have different ranges, you might test both or all three. One resource I find useful is from the USDA (https://plants.usda.gov/java/factSheet). Search for your plant and see what you find. On this page, if you search for a common name, and not the scientific name, you have to change the little menu below the search field. When the page for that species comes up, you have to look for the plant guide and fact sheet links on the page. They are sort of small.

You'll also need to decide how you plan to change the pH. There are various ways gardeners do this, and you'll want to do some research there. Let me know if an internet search doesn't help, and I'll make some suggestions. (By the way, "extension agencies" are good sources of information. There are, of course, less reliable sources!). One thing to think about is how long the additive might take to work. For example, adding sulfur seems to work by influencing the bacteria in the soil, and it may take a while for that to change the pH. Watering the soil directly with something acidic or basic would be faster, but you want to be sure you can disperse the liquid throughout the soil and not just dump it on the base of the stem.

OK, team, keep thinking and let me know what you learn!

Dr. P

Hello Dr. P,

To answer your first question, Soil is interesting to us because depending on what’s within the soil, it can have different minerals, vitamins, and nutrients which are needed for specific plants to grow, and can show the effects of several different soils on plants in specific geographical locations. 

Now, addressing your pH questions, within our chemistry class we did learn a little about pH. We are aware of the pH scale from 1-14 and how something can be acidic or basic and that water is neutral. Within biology, we have also learned that pH can effect cell function and protein composition. We are interested in pH because we wanted to try something that was different from our other classmates and because it seems more like a realistic research (for example, if there were plants living in an area with acid rain we could see a general overview of the effects it would have on a certain plant species). 

Another aspect of soil that seems interesting to us is varying nutrient levels; for example how levels of nitrogen, or other nutrients, effect plant growth. 

We have a variety of plant species which are available to us, including Buckwheat, Peas, Alfalfa, Pearl Millet, Radish, Ryegrass, Nasturtium, and Soybeans. We have PASCO pH probes available and pH paper slips. We will be doing this project until around mid April.

Thank you for responding so fast. We hope we answered your questions efficiently! 
Andria, Meredith, and Sophie