Greenman28 - that is more lime than I'll use in a lifetime. I have to be honest - I do organic grows, and I really don't pay much attention to PH most of the time. I've had containers that had a little lime vs. another similar planting that didn't, and neither of them held any distinct advantage over the other, when it was all said and done. I'd rather mix a nice rich mix, and barring any super out of whack PH shift, just take my chances. If I had synthetic ferts and a 5-1-1 mix, maybe I'd need to be a bit more studious. But while I DO check PH, I usually don't sweat it. Just not liking the idea of wasting a batch of fine ingredients.

Okay--revising the experiment for use of plants (poinsettia or ivy): I think that even the poinsettia would show changes during the three week period, but I would be worried about leaf drop/loss with the poinsettia. You probably should do the following during the experiment: 1) count the number of leaves on each plant. If you are within a leaf or two, remove a leaf or two from the leafier plant near the bottom (the worst-looking leaves) to make the number even. Do this before you start the experiment. 2) Weigh the plants. The analysis might not show any differences between the two regimens in terms of net growth, but when divided by weight might show a difference. Try to make sure that the plants start with approximately equal soil moisture levels--you could use a soil moisture meter to make sure that this stays the same. Weigh the plants every time you measure them, and if you can measure soil moisture, do that every time as well. An inexpensive proxy for a soil moisture measurement would be to place a square or circle of paper towel or coffee filter on to the surface of the soil, and measure how long it takes for the paper to become damp. 3) The place where you should see significant change is not perhaps in overall length of the plants, but the length of the stems between leaves (length between leaf nodes). To measure this difference effectively, put a small piece of twist-tie around the bases of the leaves you want to measure between so that you can find those leaves and stems again. Don't make the twist-tie very tight. You could use yarn and tie it loosely, as well. Don't make the tie or yarn pieces any bigger than absolutely necessary. If you wanted to be really systematic, you could get those little jewelry price tags that attach with a thread loop and number the tags. For your introduction and conclusions, you will want to look up information on the types of light (just like I mentioned with the seed experiment) and information on "etiolation". Etiolation, or lengthening of the stem between leaf nodes is what you would expect to see with a lack of light or with the "wrong" kind of light. The suggestions I made about using a light meter still hold, because another question that should be asked is whether it's the distance to the light source that may cause lengthening. By weighing the plants at each point, you can also control for additional biomass (plant growth) production. My guess is that the plants in both groups would be about the same--but that the stems and leaves under one treatment would be thinner and longer. If you really want to have fun with the biomass portion, at the end of the experiment, compare the differences in the plants visually (and note those differences), then dump the plants out of their pots, rinse the plants clean of as much soil as humanly possible, and leave the plants to dry. THEN weigh the plants and compare the masses. Which treatment, if any, produced the most biomass? Was there any difference in the size of the root mass? I realize that with the exception of weighing, these observations are more subjective and qualitative, but it could lead to more sensible data analysis and better subsequent experimental proposals. Don't forget to compare the color and quality of the leaves in both plants: one group of plants will probably have leaves that tend more toward yellow, and one more toward green. You could use something like a process color chart or embroidery floss sample card to describe the differences in color more accurately. I hope that you aren't absolutely overwhelmed by all this--I get into science and things just take off...

Curious about a couple of things. Why litmus paper? It will not indicate much will it? Most soils should just give a purple color. It changes blue about 4.5 and red about 8.3 doesn't it? The school should have a glass container and filter paper (A tall kitchen glass and some good coffee filter might work). Put some soil in the cylinder with distilled water and shake it up. Filter it. Stick a cheap borrowed meter in the filtrate. That is about as good as you would get, I should expect.

"One last thing is for the student to know why their experiment is important in the real world." One of my problems with the original hypothesis of which kitchen scraps would a worm prefer is how that makes a difference. It's not practical to separate food scraps into separate components. You might show that worms prefer watermelon rinds to beans but have you ever heard anyone complain about the amount of watermelon rinds causing problems at the landfill even after the 4th of July picnic? In this world of 'going green', I think I'd look at items that do present problems at the landfill but should not. A recycling company wants the easy to recycle stuff like newspaper, magazines, junkmail and old telephone books. Even in our city where we now have an active recycling initiative for paper and plastic we have things that are routinely sent to the landfill. A couple things come to mind. One is the papertowels from a restaurant or airport restroom. You could probably even get the information from the airport to compute the tonnage of waste paper they deal with. Another is disposable diapers -even though human waste is probably not something I would think a young child should be exposed to. And I'm not sure how well the worms can handle decomposing diapers anyway. A better choice would be lawn scraps. Particularly now that this is the time of year people will sending tons to the landfill instead of composting it themselves. You could even separate the lawn refuse into pure grass clippings vs chipped shrubbery scraps. I am aware that these will heat up and all that but you can do a week of precomposting them all after innoculating them with a measured amount of casting tea before adding the worms. The experiment would then not be a preference study but rather one of efficiency. Perhaps a mixture as another variable. After a specified time, sift the vermicompost for castings and compare with unprocessed material. You can do both bulk and weight comparisons.