Discussion

This experiment served as a preliminary investigation to examine the food preferences of red wigglers, Eisenia foetida. Worms are an important component of the ecosystem because they break down organic wastes, which provide fertile soil for living plants. Therefore, these worms can be useful in composting bins in a process called vermicomposting (Dickerson 2004). Vermicomposting, or composting with worms, is a useful technique to recycle human food waste, yard waste, and paper products. Worm castings, which result from the digestion and secretion of organic material through the worm, create a nutrient rich soil that is ideal for plant growth. Worm castings often contain “5 to 11 times more nitrogen, phosphorus, and potassium than the surrounding soils” (Dickerson 2004). Therefore, using worms to decompose organic matter mutually benefits earthworms through providing a food source and plants, which benefit from their nutrient enhanced soil. By placing red wigglers into soils with different sources organic matter, we hoped to determine the food preference of red wigglers between grass clipping and newspaper clippings. This information may be useful when using earthworms as part of a composting bin because the proper ratios of organic matter could enhance the survival and reproduction of red wigglers, thus creating a more nutrient rich soil.

Our first hypothesis that red wigglers would prefer soil with organic matter over soil without organic matter was supported with data from our experiment (Figure 1 and 2). It was determined that red wigglers preferred soil with an organic source because a significant number of worms were found in the soil containing organic matter (grass or newspaper) compared to the soil containing potting soil, which lacked a source of organic material. Since worms rely on a source of organic matter to survive, these results were expected. In addition, these results also provide evidence that earthworms prefer soil with an organic source over soil without an organic source. From these results, we were able to test whether a red wiggler would prefer soil containing grass clippings over soil containing newspaper clippings.

By setting up bins with soils with two organic sources, where half the soil contained grass clippings and half the soil contained newspaper clippings, we were able to investigate the preference of red wrigglers. This was determined by their location in the bin after forty-eight hours. Since the difference between data sets of worms found in grass containing soil vs. newspaper containing soil showed no statistical significance, the hypothesis that worms would prefer grass containing soil over newspaper containing soil was not supported. From this data, it could be speculated that earthworms will simply exist in soil containing organic matter, regardless of its source.

However, prior investigations provide evidence that factors beyond organic matter influence the location of worms in soil. These factors include the soil’s moisture, texture, depth, pH, and nitrogen content (Curry 1998). This experiment controlled the variables of moisture, texture, and depth by keeping these factors constant for both soils containing grass or newspaper clippings. The pH and nitrogen content of soils containing grass vs. soils containing newspaper could differ between soils and thus influence the location of earthworms during the experiment. While differences exist between species, it has been determined that worms generally prefer soil with a pH in the range of 5.0-7.4 (Curry 1998). Our hypothesis that red wigglers would prefer grass clippings over newspaper clippings was based on the assumption that the dyes in newspaper could contribute to a more acidic soil, which could deter worms from choosing newspaper as a food source. However, the pH measured for each soil type was within the 6.0-7.0 range and therefore probably did not influence the location of worms in this experiment. The difference in nitrogen content between soil containing grass and soil containing newspaper was not large in each trial, so nitrogen levels also probably did not play a role in the worms’ location. Since the factors contributing to worm soil location were not significantly different between soil types and there was no significant difference of the number worms found in a specific soil, a preference for grass or newspaper as a food source was not evident in this experiment.

Extensions of this experiment can easily be completed to investigate the food preference of earthworms. For example, various organic sources could be tested by repeating the experiment and adding another organic source to the soil. Some examples could include fruit scraps, leaves, vegetable scraps, or manure. Measuring the preference of worms of each organic source would be useful to determine the ratio of organic matter to add to a composting bin. By creating a favorable environment for worms, the quality of soil can also be enhanced by facilitating to worm survival and reproduction. Also, the preference of organic texture can also be useful to creating a healthy environment for worms. It may be useful to finely chop waste so that worms can consume and digest organic materials more easily. Finally, different species of worms could be used to determine if they differ in food preference. Our experiment used red wigglers (Eisenia foetida), but another worm species may yield different results. Many extensions of this experiment could provide useful insight on the dietary and soil preferences of worms.

Using a simple procedure, we completed this preliminary experiment to determine the food preference of earthworms. While our data supports the hypothesis that earthworms will prefer soil with an organic source over soil lacking organic material, the data did not reveal a worm preference between soil containing grass or newspaper. There are a few modifications that could be made to improve this experiment. First, we used the same worms for each trial, which could contribute to the worm location during each trial. Perhaps using a new set of worms would result in different data. Also, if more trial were conducted, a greater amount of data collected could reveal trends in worm soil preference. Finally, a test of the soil’s pH and nitrogen content before and after the addition of worms could provide evidence of the worms’ efficiency to decompose the organic source.

Overall, this experiment provides evidence that earthworms decompose organic material found in soils. A preference between soil containing grass or newspaper was not determined during this experiment. This does not diminish the importance that worms, such as red wigglers, play in the ecological cycle by decomposing organic material. Humans can accelerate and exploit the decomposition process by using worms in composting bins, a process known as vermicomposting. More research would need to be completed to determine the optimal environment and food source for red wigglers. Regardless of a preference for a specific organic source, worms provide nutrient rich soils for plants through the decomposition of organic materials. Determining worm food preference would serve to accelerate decomposition and promote the health of worms to create an environment where both worms and plants can prosper.