Soil Drainage and Water Retention Experiment
A healthy soil is key to insuring proper drainage and water retention. Without proper drainage, soils become too saturated leading to fungal and disease problems as well as little to no aeration for roots or microbial life. Soils with little water retention can become dry and compacted, equally leading to no aeration and ultimately causing poor drainage and standing water. Whether you have soil that is too saturated or too dry and compacted, plants will not grow well and life within the soil cannot thrive. A fun and easy experiment can show how different soils handle water.
· 3 to 4+ two-liter soda bottles.
· 3 to 4+ different soils, both from areas with poor soil and areas that seem to have abundant plant growth. Get enough to fill the top part of the soda bottle (1.5 to 2 cups). Here are some ideas on soil to collect;
o Your own garden soils
o Soil from a local flourishing agriculture field (with or without crops growing)
o Soil from a seemingly non-touched area such as in the mountains, forests or in nature
o Soil from a local park (both high traffic and landscape areas)
o Sandy soil from a beach
o Soil from a non-paved parking lot
o Soil near the side of a sidewalk or high traffic walking area
o Soil from an area that only seems to grow weeds
· Rinse bottles out and take labels off. Cut the soda bottle and place cut top as shown in the pictures below.
· Put each soil into the top of the soda bottle, trying your best not to push on or compact the soil too much. You want the soil to be as close to what it naturally was when collected. You can keep the lid on until you’re ready for the experiment to reduce soil lose.
· Label each bottle with the location the soil was collected from and a short description on the area (i.e. compacted, cotton field, parking lot, forest, etc.)
· Take the lid off the bottle if used, and then slowly poor water into each (enough to fill to the rim). It is best to do this one by one as some will quickly drain before you've even finished filling the others.
· Have your kids take note on how each is draining and decide which soils are healthy and unhealthy.
What should you be seeing?
The soils collected will do 1 of 4 things; (1) drain very quickly, barely sitting in the soil. (2) drain moderately, soil becomes fully saturated but water doesn’t puddle on top for long. (3) drain very slowly, water sits on the top for a while and may just barely drip out the bottom. (4) no drainage at all, water puddles on top and doesn’t get through at all.
(1) Very sandy soil has little to no water retention and will quickly drain water within seconds. This doesn't allow the soil to become properly saturated and also leads to nutrients being too quickly leached.
(2) Healthy soils with proper soil structure and aeration will moderately drain. The water has time to fully saturated the soil without leaving standing water on top. Any nutrients applied with the water are properly moved through the soil and given time to cycle through the system before leaching.
(3) High traffic soils can become compacted, leaving no space for water and air. This leads to water sitting on top, attracting pests and disease. Soil is clumpy or hard, and if it has a high clay content can cause large cracks. Water may take hours or days to fully drain.
(4) Also, in high traffic and compacted areas.