Which element has the greatest influence on decomposition: water, dirt, or heat?
I think dirt will have the greatest influence on decomposition because of the micro-organisms found in dirt. After dirt, I think heat will have the most influence. Cold preserves organic material, it makes sense heat would decompose organic material. After dirt and heat, I think water will have the next greatest influence on decomposition because water is a naturally destructive force. With these thoughts in mind I believe the jars will show signs of decomposition in the following order:
To conduct this experiment, I will place an equal amount of produce in six canning jars, with each jar containing the same produce. Once the six jars have produce in them, I will put one cup of water in two of the jars and fill two jars the rest of the way up with dirt. Then I will tightly close all six jars. Jars 1, 2, and 3 will be placed outside in full sun. Jars 4, 5, and 6 will remain inside out of direct sunlight and away from any sources of heat. I will record the daily high temperature, so I can monitor how much heat the outside jars are exposed to. I will take pictures of the jars frequently so that I can monitor the decomposition occurring in each jar. At the end of each week, I will make a written observation about the changes I see in the produce. I will collect the pictures and observations in a log on my website. Then I will present my findings as my midterm science project using the Merlot.org format that is required. I will also keep my findings on my website for future review.
At the end of the third week I am comfortable saying that I have disproved my hypothesis, which stated the jars would show decomposition in the following order:
I thought the produce in the dirt would decompose faster because of the micro-organisms present in the dirt. However, the two jars containing dirt are the least decomposed of all six jars. I thought the next greatest influence would be heat, with the outside water and outside only produce jars decomposing faster than the inside jars. This was only partially correct. The outside water jar did show greater signs of decomposing than the inside jars, however the inside water jar showed greater decomposition than the outside only produce jar. The jars currently appear to be decomposing in the following order:
This shows that water is having the greatest influence on the decomposing of the produce. Heat seems to be the second most influential factor. Dirt seems to be the least important.
Upon further research, it has come to my attention that there are other factors that need to be considered. One of these factors is the oxygen present during the decomposition process. When designing this experiment, I chose to use jars with lids for my containers. I chose to do so in order to keep the fruit flies in the house to a minimum. Limiting the oxygen available during the decomposition process does not stop decomposition, but it changes the chemical process.
There are two types of decomposition: anaerobic and aerobic. Anaerobic decomposition occurs without oxygen. Aerobic decomposition occurs with oxygen (Texas A & M, 2009). The oxygen present determines whether organic matter decomposes with the help of living creatures, or through putrefaction. Because I sealed the jars with lids I am denying oxygen to the environment and engaging in anaerobic decomposition. There are a number of disadvantages to using this decomposition method. First and foremost is the smell. This smell is caused by the hydrogen sulfide and compounds which contain sulfur (Texas A & M, 2009). This is what caused the pressure build up and smell in Jar 4. Another large disadvantage to this method is the amount of time compost must be held before it is safe to use. Anaerobic decomposition produces less heat than aerobic decomposition. This heat is the key to killing pathogens and parasites. The pathogens and parasites will eventually be eliminated; however, it takes at least six months (Texas A & M, 2009).
The smell as well as the potential to contain pathogens and parasites, makes my chosen method of decomposition less effective than aerobic composting. Aerobic decomposition is the method most commonly found in nature and is the process that is occurring in my composter. In order to effectively test variables that influence the production of my composter, I have to test the method of decomposition that is utilized by the composter.
Therefore, if I were to conduct this experiment again there are a number of things that I would change. I would begin by finding a method of temperature control that is not inside the house. This would allow for oxygenation of the material without the fruit flies driving my family insane. Also, as the temperature tracking shows, around the second week mark the temperature controls switched. By this I mean, it became consistently warmer inside the house than outside. I believe this influenced the rate of decomposition in the outside jars. I think this could be countered by beginning this experiment at the beginning of the summer instead of the end. Even without the outside temperature drop, I would have liked a way to better gauge the temperature of the jars. I tracked the outside high temperature, but this does not tell me about the temperature inside the jar.
References
Texas A & M Agrilife Extension (2009). Earth-kind landscaping: Chapter 1, The decomposition process. Retrieved from https://aggie-horticulture.tamu.edu/earthkind/landscape/dont-bag-it/chapter-1-the-decomposition-process/