Caustic CompostCaustic Compost

by Meby Me

Science fair 2010Science fair 2010

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 soil around the house is very bad. It has lots of clay and rocks, so my dad is adding grass of 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

Internet research showed that plants need nutrients in Internet research showed that plants need nutrients in the soil to grow, as well as water and carbon dioxide. the soil to grow, as well as water and carbon dioxide. Plants also need a neutral pH in the soil to grow best.Plants also need a neutral pH in the soil to grow best.

pH is a measurement of how pH is a measurement of how much acid is in somethingmuch acid is in something

pH of the soil can be changed pH of the soil can be changed by chemicals or by plants.by chemicals or by plants.

(See citations section for details)(See citations section for details)

QuestionQuestion

What are the effects of leaf type on compost pH?What are the effects of leaf type on compost pH?

This could also be written as…This could also be written as…

Does the type of leaves added to a compost pile Does the type of leaves added to a compost pile change the pH of the compost?change the pH of the compost?

HypothesisHypothesis

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

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 each leaf type. Gather 1 liter (approx) of each leaf type. This includes aspen, poplar, maple, walnut, This includes aspen, poplar, maple, walnut, apple, fir needles, and grass clippings.apple, fir needles, and 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

Ph OF VARIOUS TYPES OF LEAVES MIXED WITH POTTING SOIL

LEAF TYPE

ResultsResults

The data shows that the pH of the walnut leaves The 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.

It was surprising to see that almost all of the soil It was surprising to see that almost all of the soil samples had very close to the same pH. samples had very close to the same pH.

ConclusionConclusion

This experiment predicted that if walnut leaves This experiment predicted that if walnut leaves were added to potting soil, then the pH of the were added to potting soil, then the pH of the mixture would be lower than plain potting soil mixture would be lower than plain potting soil because walnut trees seemed to prevent because walnut trees seemed to prevent growth of other plants. growth of other plants.

The data showed that walnut leaves lowered the The data showed that walnut leaves lowered the pH the most - from neutral to just slightly pH the most - from neutral to just slightly acidic. acidic.

Conclusion ContinuedConclusion Continued

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

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 the project will be to actually plant Phase 2 of the 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.