Rain Simulator for Drainage Testing
When designing mixes, one of the
most important aspects to consider is structure. While there are treatments to
amend a soil’s pH and EC after the fact, the structure that leaves the mixing
line is the structure that you are stuck with, for better or worse. This is
crucial because large aspects of a soil’s performance are determined almost
entirely by structure. The size of the particles and how they fit with one
another can determine how a soil settles, its weight, and, most importantly,
how it drains.
Drainage
in soils is a result of how much water the media holds, and how tightly it
holds on to it. Particle size has everything to do with this characteristic.
Sand, for example, is made up of fairly large particles compared to clay; because these larger particles can’t pack as tightly together, there are tiny
pockets of air in the media. This pore space is the part of the media that can
be occupied by water. Large pore spaces allow the media to take up water
quickly, but also allows it to leave quickly. In a media with small particles and pore
spaces, like clay, the water will be taken up slowly and retained for a longer
time. In other words, it drains more poorly.
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| CHSTR's Rain Simulator |
In the design I used, a 2-gallon nozzle was suspended over each drum, with a hole at the bottom. Water was collected from each hole in plastic carboys over a set amount of time. The amount collected in this window of time gives us insight into how quickly the mixes drain and gives us another data point to consider when designing new mixes or testing the performance of older recipes.
Michael Conway- Midwest Trading's Horticultural Soils Intern
