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Does Organic Material Affect The Absorbency Of Water In Soil?

Researched by Stefanie D.



The purpose of this experiment was to determine how organic material affects the water absorbency of soil.

I became interested in this idea when I realized that lack of organic material might be drying out our soils.

The information gained from this experiment will aid gardeners by determining which organic material will benefit their plants the most.



My hypothesis was that 3/4 Peat moss would absorb the water the most.

I base my hypothesis on an article that Dale H. Vitt wrote, He said, " Peat Moss absorbs water through their dead cells and because Peat moss is used for transporting plants. That made me think that Peat moss would absorb water the most.





The constants of this experiment were:

  • The same size and type of pot 
  • The amount of sand, 
  • Amount of manure, 
  • Amount of peat moss, 
  • Temperature of room, 
  • Amount of water, 
  • The amount of time, 
  • The amount of total material in each pot.
The manipulated variable was the type of organic material and amount.

The responding variable was the amount of water absorbed by the soil mixture. 

To measure the responding variable the water drained from the soil was measured exactly 12 hours after the water was initially added. 




2000grams  Sand 
750grams Manure 
750grams  Peat Moss
Plastic pots
7 Plastic spoons
7 Plant saucers
7liters Tap water
1 Measuring cup (capacity 1 liter)
1 Triple balance beam scale




1. Gather all materials at place the pots separately on the table and place a saucer under each of the pots.
2. Measure out 500 grams of sand and pour into a pot and label Sand.
3. In another pot measure and place 125 grams of peat moss and 375 grams of sand into the pot and mix thoroughly. Label it 1/4 peat moss.
4. In another pot, measure 250 grams of peat moss and 250 grams of sand and place into another the pot. Mix Thoroughly. Label it 1/2 peat moss.
5. In another pot measure 375 grams of peat moss and 125 grams of sand and place in an empty pot. Mix thoroughly. Label it 3/4 peat moss.
6. In another pot measure 125 grams of manure, and 375 grams sand and add to a new pot. Mix thoroughly. Label this one 1/4 manure.
7. In another pot measure 250 grams of manure and 250 grams of sand and add to another of the empty pots. Mix thoroughly. Label this one 1/2 manure.
8. Measure 375 grams of manure and 125 grams of sand. Mix thoroughly, then label this one manure.
9. Place a plant saucer under each pot to catch the water.
10. Place 1 liter of water into each pot.  Gradually mix the water in. 
11. Wait 12 hours
12. Measure how much water came out into the saucer then subtract this from how much      initially added
13. Clean out all pots and start with new materials.
14. Repeat steps 1-12 2 times.




The original purpose of this experiment was to find out if organic material affects the absorbency of soil.

The results of the experiment were that in my first trial the 1/2 peat moss absorbed 760ml of water therefore absorbing the most and sand absorbed 387ml therefore absorbing the least. In trial 2, 1/2 peat moss absorbed the most again at 648ml and 1/4 manure absorbed the least at 354ml.

See The Table and Graph




My hypothesis was that 3/4 Peat moss would absorb the water the most and therefore affecting how much was absorbed.

The results indicate that this hypothesis should be rejected because I thought 3/4 peat moss would absorb the most but 1/2 absorbed the most.

Because of the results of this experiment, I wonder how plants would grow in the different mixtures.

If I were to conduct this project again I think that I would have tested normal potting soil too so I would know how much the absorbency of water was needed for soil. I would also use more water applied it more slowly and repeatedly to have a larger accuracy. I would also do more trials.


 Organic material is very important to agriculture. Farmers and gardeners use it to increase the nutrients in their soil. So by mixing organic material in your soil, you can highly increase the quality in whatever your product is.

Organic material is composed of decaying plants and animals. Microscopic fungi and bacteria cause the decay process. Amorphous, a type of loose organic material, forms soil particles called humus. Humus usually is dark brown or black, and it holds large amounts of water. Organic material puts nutrients into soil. In most mineral soils, only 6% to 12% of the volume of particles is organic.

Water is a necessity for growing plants. Water’s chemical formula is two parts hydrogen, one part oxygen. If water is pure, then it has no odor, is tasteless and is clear. Water is used for irrigation of plants if the soil does not have enough moisture naturally.  Plants need water because of something called photosynthesis. For every carbohydrate, which comes from photosynthesis, you need one molecule of H2O, or water. So without water, there would be no carbohydrates, no photosynthesis, and no food at all.

Peat moss, bog moss, or sphagnum moss grows in bogs and swamps all over the world. Peat is over 300 species of moss plants that can grow over 30 inches or more. Peat has stems and leaves that have special cells that absorb water very well. When Peat dies, it is compressed into peat moss or fuel. Peat moss can be used in gardening, or since it absorbs water so well, it is sometimes used for transporting plants. 

Sand is composed of small grains of loose, mineral materials. It is formed when rocks are broken down by weathering and erosion. Sand is a very important part of soil. It is usually found on the shores of lakes and the sea. 

Manure is animal or plant waste. Manure is combined with humus. Manure is high in nitrogen, which is a very important part of protein, phosphorus, which is absorbed from the soil by manure, and potassium, which is found with minerals. Manure is used for loosening soil and is used also to take in water.

Without organic material, soil would lack nutrients and the quality of the soil would decrease.




"Peat Moss," Encarta Encyclopedia 2000

"Manure," Encarta Encyclopedia 2000

"Sand" Encarta Encyclopedia 2000

"Soil" Encarta Encyclopedia 1996

"Soil" The World Book Encyclopedia.   1999. Vol.18. Pp.573-576

"Water" Encarta Encyclopedia 2000

Winkler, Suzzanne  and Rodgers, Mary M.  Soil. United States: Lerner Publications Company,   1994 

 Vitt, Dale E. "Peat Moss," World Book Encyclopedia. 1998 . Vol. 15 Pp. 225


I want to thank my mom for helping get my supplies and giving me tips for my project. I would also like to thank Mr. Newkirk for having after school work sesions.  If these people did not help me, then my project would not be as complete as it is now.


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