Caustic CompostCaustic Compost

by Megan Harrisby Megan Harris

IntroductionIntroduction

My family just moved into a new house, and the My family just moved into a new house, and the soil around the house is very bad. It has lots of soil around the house is very bad. It has lots of clay and rocks, so my dad is adding grass clay and rocks, so my dad is adding grass clippings and leaves to the soil to help it grow clippings and leaves to the soil to help it grow grass in the future.grass in the future.

I’ve also noticed that nothing growsI’ve also noticed that nothing grows under my grandma’s walnut trees under my grandma’s walnut trees and her pine trees.and her pine trees.

Background ResearchBackground Research

I checked on the Internet and found out that plants need I checked on the Internet and found out that plants need nutrients in the soil to grow, as well as water and nutrients in the soil to grow, as well as water and carbon dioxide. Plants also need a neutral pH in the carbon dioxide. Plants also need a neutral pH in the soil to grow best.soil to grow best.

I found out that pH is a I found out that pH is a measurement of how muchmeasurement of how much acid is in the soil. I also acid is in the soil. I also found out that the pH of the found out that the pH of the soil can be changed by soil can be changed by chemicals or plants.chemicals or plants.

QuestionQuestion

Now I’m wondering…Now I’m wondering…

Does the type of leaves used in compost change Does the type of leaves used in compost change the pH of the soil they are added to?the pH of the soil they are added to?

HypothesisHypothesis

I predict that walnut leaves and fir needles will I predict that walnut leaves and fir needles will lower the pH the most because nothing grows lower the pH the most because nothing grows under those types of trees.under those types of trees.

Materials ListMaterials List 2 liters distilled water2 liters distilled water 1 liter each of walnut leaves, apple leaves, aspen 1 liter each of walnut leaves, apple leaves, aspen

leaves, maple leaves, poplar leaves, fir needles, and leaves, maple leaves, poplar leaves, fir needles, and grass clippingsgrass clippings

8 gallon-size Ziploc bags8 gallon-size Ziploc bags 24 clear plastic cups24 clear plastic cups 24 plastic spoons24 plastic spoons 20 liter bag of potting soil20 liter bag of potting soil pH meterpH meter scissorsscissors

ProcedureProcedure

1.1. Gather 1 liter (approx) of every type of leaf Gather 1 liter (approx) of every type of leaf in my grandma’s yard. This includes aspen, in my grandma’s yard. This includes aspen, poplar, maple, walnut, apple, fir needles, and poplar, maple, walnut, apple, fir needles, and grass clippings.grass clippings.

2.2. Place each type of leaves in a separate Place each type of leaves in a separate gallon-size Ziploc bag.gallon-size Ziploc bag.

3.3. Let the leaves decompose inside the sealed Let the leaves decompose inside the sealed bags for 4 weeksbags for 4 weeks

Procedure ContinuedProcedure Continued

4.4. Prepare the cups by mixing 150 ml of potting Prepare the cups by mixing 150 ml of potting soil with 100 ml of distilled water in each soil with 100 ml of distilled water in each cup. Mix with a clean plastic spoon. cup. Mix with a clean plastic spoon.

5.5. Use scissors to cut up each type of leaves Use scissors to cut up each type of leaves into pieces no larger than 1 cm. Mix 100 ml into pieces no larger than 1 cm. Mix 100 ml of each type of leaves into three soil cups. of each type of leaves into three soil cups. Mix with a clean plastic spoon each time.Mix with a clean plastic spoon each time.

6.6. Put no leaves into the three control cups.Put no leaves into the three control cups.

Procedure ContinuedProcedure Continued

7.7. Measure the pH of the soil/compost mixture Measure the pH of the soil/compost mixture in each cup, rinsing off the meter with in each cup, rinsing off the meter with distilled water in between each test.distilled water in between each test.

8.8. Record the results and keep the cups for Record the results and keep the cups for Phase 2 of testing.Phase 2 of testing.

Variables and ControlsVariables and Controls

Independent Variable : type of compostIndependent Variable : type of compost Dependent Variable: pH measurementDependent Variable: pH measurement Constants: amount of soil, amount of compost, Constants: amount of soil, amount of compost,

amount of water, type of cup, length of time to amount of water, type of cup, length of time to decompose, stored at same temperature, decompose, stored at same temperature, measured in the same waymeasured in the same way

Control: cup with soil only and no compost Control: cup with soil only and no compost

DataData

5.8

6

6.2

6.4

6.6

6.8

7

Control Apple Aspen Maple Poplar Walnut Fir Grass

ResultsResults

My data shows that the pH of the walnut leaves My data shows that the pH of the walnut leaves and soil mixture was the lowest, which means and soil mixture was the lowest, which means that walnut leaves have the most acid.that walnut leaves have the most acid.

I was surprised to see that almost all of the soil I was surprised to see that almost all of the soil samples had very close to the same pH. I samples had very close to the same pH. I thought walnut and fir would be much more thought walnut and fir would be much more acidic.acidic.

ConclusionConclusion

In this experiment, I tried to determine if In this experiment, I tried to determine if different types of composted leaves affected different types of composted leaves affected the pH of the soil they were mixed into. My the pH of the soil they were mixed into. My data showed that walnut leaves lowered the pH data showed that walnut leaves lowered the pH from neutral to just slightly acidic. My from neutral to just slightly acidic. My hypothesis was partly supported, because I hypothesis was partly supported, because I predicted that both walnut leaves and pine predicted that both walnut leaves and pine needles would make acidic soil. I was needles would make acidic soil. I was surprised that the walnut leaves were not very surprised that the walnut leaves were not very acidic.acidic.

Future ResearchFuture Research

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