Landscape Architect & Specifier News

JAN 2019

LASN is a photographically oriented, professional journal featuring topics of concern and state-of-the-art projects designed or influenced by registered Landscape Architects.

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Above: Freshly installed soil plots. From right to left - Plot 1: BioG Mix, Plot 2: 60:40 Haydite: in situ, Plot 3: Ohio Department of Natural Resources' Standard soil. Left: This is the Double Ring Infiltrometer by Turf Tec International. It measures the downward flow of water through the soil and includes a timer to correlate irrigation time to infiltration rate. This test was from July 2018 in Plot 1, which maintained original infiltration rates, while Plot 3 silted over and lost over 75% of the original infiltration rate. My Research Because the engineering perspective of soil is structural, there isn't as much attention payed to the materials that pass the #200 sieve. They simply call them "fines" and try to keep them to a specified minimum, often below 10%. In horticulture, we define and measure below the #200 sieve, as we are interested in how much and what type of clay is in the soil, to create a better environment for root systems. Many landscape plants in the Midwest (and many other regions) do much better with clay contents between 15 – 40%, even well into 50 or 60%. Traditionally, much of the research done on stormwater management practices has been by engineers who tested the infiltration rates, saturation rates, and dewatering times. They tested physical filtration capability, chemical filtration and the results pointed to high sand, low fines. This makes sense to them, as the goal is to filter the water quickly, and move it along. Somehow, some horticulturists got on board and said, "OK, we'll find some plants that will tolerate this planting condition to make a "rain garden."" So here is the condition: 32 Landscape Architect and Specifier News

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