Our Topic

Why should we care about earthworms?

Believe it or not, earthworms play a large role in sustaining agriculture and the greater environment by maintaining the soil. Annually, earthworm populations can consume around 2 tons of dry matter that they then process and mix with the soil. Not only does this mixing help promote crop growth, but it also supplies the soil with valuable nutrients such as potassium, phosphorus, calcium, nitrogen, zinc, and more. Soil that is passed through earthworms will have a neutral pH as well as a high concentration microbes which benefit the decomposition of crop residue. Earthworm burrows also help aerate the soil and increase soil porosity. This allows for more oxygen and water to infiltrate the soil and better reach plant roots. Along with this, earthworms consume a variety of organisms, such as nematodes and protozoa, that live in the soil. For these reasons and many more, earthworms play a pivotal role within the soil and their presence is certainly valued!

 

What is clay soil?

Clay soil consists of fine mineral particles and some organic material. The texture of clay soil is very sticky and moist because the mineral particles do not have much space, making drainage difficult. Clay soil provides nutrients such as phosphorous and potassium which help with plant growth. The high nutrients from clay soil come from negatively charged particles from the soil that attract positively charged particles including calcium, potassium, and magnesium. Though clay soil is very compacted and does not allow for much air, it retains water and moisture well. Overall, clay soil provides earthworms with an environment to live and thrive in.

 

Can you tell me more about earthworms?

Earthworms are boneless invertebrates that travel by contracting and relaxing their segmented bodies. They absorb oxygen through their skin so they require moist environments. When it rains, they will often move to the surface to avoid suffocation. Though in the wild earthworms only live around 1 to 2 years due to environmental factors, they have been observed to live up to 10 years in a protected environment!

There are thousands of species of earthworms but they are all grouped into 3 categories: epigeic, endogeic, and anecic species. Epigeic species or litter dwellers live and eat amongst the leaf litter and are not particularly common in most soils. Endogeic or topsoil dwellers live within the upper 5 to 7cm of the soil. They ingest large amounts of soil and create horizontal burrows that support agriculture. Anecic species or subsoil dwellers live around 1.5 to 2 meters in the soil in permanent vertical burrows. They travel to the surface to cap their burrows with crop residue that they bring into their burrows to consume.

 

What is our experiment exploring?

The Early Birds explored a topic based around the interaction between earthworm populations and soil textures; specifically clay soil. Clay soils are made up of fine particles that retain water and nutrients such as potassium, phosphorus, and more. Many earthworms are naturally attracted to and thus found in clay soils. This is mainly because earthworms need moisture within their soil to move and burrow in the ground. Dry, heavy, or compacted soils make life and movement difficult for earthworms.

When referencing previously collected data, we noticed that there was a large population of earthworms in a Microclimate with a large population of protozoa. Since this should be a case of predator (earthworms) vs. prey (protozoa), there should be a difference between these population sizes. We hypothesized that perhaps the Microclimate’s soil composition directly impacted the mobility and location of earthworms, causing them to group together and not spread out to consume protozoa.