Today we’re winding up our soil science experiment by seeing how much water remains in the root zone mix (and thus, available for plants to use) after a rainstorm. We’ll also add another five inches of water to the system to compare how quickly it drains into the wet soil versus how quickly it drained into the dry soil.
But first, we’re stymied by captive air–because we’re conducting the experiment in a test tube and not in nature, we’ve got some trapped air that’s preventing the soil from draining. So…out comes the drill!
A couple days later, we check in again and see how the air has returned to the pore space previously occupied by water.
After a third rainstorm, the ground is pretty well-hydrated. Does this make the latest rain drain faster or slower?
Phil wraps up the demonstration with some thoughts about why severe thunderstorms that come after a week of dry weather do nothing to help our plants and lawns. He also discusses how these soil profiles were selected for Schenley Plaza and Mellon Park.
Thanks for watching! We hope to have more science-themed demonstrations in the future. If there’s ever something about the parks you’re curious about, drop us a comment and we’ll try to answer your questions!
Yesterday’s post showed you an example of how our Management and Maintenance team constructs a soil profile for highly-trafficked areas in the parks. Part of the advantage of this kind of soil structure is that it helps to infiltrate water more effectively than some of the existing soil structures in the parks. And better water infiltration leads to reductions in things like erosion, water runoff, and water that reaches the city’s combined sewer system. Plus, the deeper the water is able to infiltrate, the more groundwater recharge will take place.
Today we’ll watch over the course of an hour as we simulate a five-inch rainstorm in the test tube. We’ll see how quickly the water reaches the drainage gravel after entering a system of completely dry soil.
Five inches of rain in ten seconds–that’s a pretty big storm!
Checking in after 4 minutes:
What do all those air bubbles mean?
25 minutes later, the water begins to hit the bridging gravel – will the sandy soil on top start to drain into the gravel too?
35 minutes later, the water is making its way fully through the system:
An hour later, water begins to leave the system. How much water will remain in the root zone mix to feed the (hypothetical) plants?
Tomorrow we’ll add even more water and compare the rate of water infiltration into dry soil to how fast it infiltrates to already-moist soil. Any guesses which will go faster?
Today we’re taking you underground! Over the next few posts we’ll be looking at how specially constructed soil profiles can help to reduce the problem of storm water runoff we’ve been talking so much about lately. Our Director of Management and Maintenance, Phil Gruszka, conducted a science experiment last week to see whether the soil profile he put in place at Schenley Plaza and the Mellon Park Walled Garden really does help infiltrate water. You can watch the demonstration unfold on video, starting with the clips below.
Phil introduces the concept of the importance of soils to the appearance and functionality of the parks:
The three components of a soil profile: drainage gravel, bridging gravel, and root zone mix, and what each one does:
Replicating the soil profile at Schenley Plaza:
Using a sponge, Phil demonstrates the importance of having deep columns of topsoil to support plants and infiltrate water:
In our next post we’ll watch what happens over the course of an hour when we simulate a five-inch rainstorm.
* Thanks to Natural Sand Company in Slippery Rock for donating the materials for this demonstration!