1. Caustic Compost by Me Science fair 2010

2. Introduction My family just moved into a new house, and the soil around the house is very bad. It has lots of clay and rocks, so my dad is adding grass clippings and leaves to the soil to help it grow grass in the future. I’ve also noticed that nothing grows under my grandma’s walnut trees under my grandma’s walnut trees and her pine trees.

3. Background Research Internet research showed that plants need nutrients in the soil to grow, as well as water and carbon dioxide. Plants also need a neutral pH in the soil to grow best. pH is a measurement of how much acid is in something pH of the soil can be changed by chemicals or by plants. (See citations section for details)

4. Question What are the effects of leaf type on compost pH? This could also be written as… Does the type of leaves added to a compost pile change the pH of the compost?

5. Hypothesis If walnut leaves are added to potting soil, then the pH of the mixture will be lower than plain potting soil because walnut trees seem to prevent growth of other plants. If walnut leaves are added to potting soil, then the pH of the mixture will be lower than plain potting soil because walnut trees seem to prevent growth of other plants.

6. Materials List 2 liters distilled water 2 liters distilled water 1 liter each of walnut leaves, apple leaves, aspen leaves, maple leaves, poplar leaves, fir needles, and grass clippings 1 liter each of walnut leaves, apple leaves, aspen leaves, maple leaves, poplar leaves, fir needles, and grass clippings 8 gallon-size Ziploc bags 8 gallon-size Ziploc bags 24 clear plastic cups 24 clear plastic cups 24 plastic spoons 24 plastic spoons 20 liter bag of potting soil 20 liter bag of potting soil pH meter pH meter scissors scissors

7. Procedure 1. Gather 1 liter (approx) of each leaf type. This includes aspen, poplar, maple, walnut, apple, fir needles, and grass clippings. 2. Place each type of leaves in a separate gallon-size Ziploc bag. 3. Let the leaves decompose inside the sealed bags for 4 weeks

8. Procedure Continued 4. Prepare the cups by mixing 150 ml of potting soil with 100 ml of distilled water in each cup. Mix with a clean plastic spoon. 5. Use scissors to cut up each type of leaves into pieces no larger than 1 cm. Mix 100 ml of each type of leaves into three soil cups. Mix with a clean plastic spoon each time. 6. Put no leaves into the three control cups.

9. Procedure Continued 7. Measure the pH of the soil/compost mixture in each cup, rinsing off the meter with distilled water in between each test. 8. Record the results and keep the cups for Phase 2 of testing.

10. Variables and Controls Independent Variable : type of compost Independent Variable : type of compost Dependent Variable: pH measurement Dependent Variable: pH measurement Constants: amount of soil, amount of compost, amount of water, type of cup, length of time to decompose, stored at same temperature, measured in the same way Constants: amount of soil, amount of compost, amount of water, type of cup, length of time to decompose, stored at same temperature, measured in the same way Control: cup with soil only and no compost Control: cup with soil only and no compost

11. Data Ph OF VARIOUS TYPES OF LEAVES MIXED WITH POTTING SOIL LEAF TYPE pH measurement

12. Results The data shows that the pH of the walnut leaves and soil mixture was the lowest, which means that walnut leaves have the most acid. It was surprising to see that almost all of the soil samples had very close to the same pH.

13. Conclusion This experiment predicted that if walnut leaves were added to potting soil, then the pH of the mixture would be lower than plain potting soil because walnut trees seemed to prevent growth of other plants. This experiment predicted that if walnut leaves were added to potting soil, then the pH of the mixture would be lower than plain potting soil because walnut trees seemed to prevent growth of other plants. The data showed that walnut leaves lowered the pH the most - from neutral to just slightly acidic. The data showed that walnut leaves lowered the pH the most - from neutral to just slightly acidic.

14. Conclusion Continued The hypothesis was partially supported because although the pH was lowest with the addition of walnut leaves, the change in pH was not significant.

15. Future Research The acid in the walnut leaves was not enough to cause plants not to grow under the trees. There must be something else in the leaves besides acid that prevents seeds from growing. Phase 2 of the project will be to actually plant seeds in the soil cups and see which type of compost produces the most plant growth.