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| Nina Bassuk's trees are planted in CU-Structural Soil® amid pavement. |
From the point of view of pavement, trees are not good neighbors. The loose soil needed by tree roots can’t support sidewalks and roadways. And if tree roots can’t find enough moisture at depth, they erupt at the surface and buckle the pavement.
A pragmatic Nina Bassuk ’74, director of Cornell’s Urban Horticulture Institute, and then graduate student, Jason Grabosky, MS ’96, PhD ’99, developed CU-Structural Soil® with the needs of pavement and urban trees—in mind. CU-Structural Soil® is composed of 1-inch crushed stone that forms a weight-bearing lattice (strong enough to support the pavement and traffic above) as well as ample void space (called macropores) among the rocks for the needs of tree roots (soil, air, and water), a very small amount of water absorbing hydrogel (to help the soil stay uniformly mixed with the stones), and, of course, some actual soil (a clay-loam will do as long as some organic matter is included).
As strong as it is, the rocky lattice structure still leaves plenty of empty space at depth for roots “to explore,” as Bassuk likes to say. So the roots are less likely to invade upper levels of their “assigned space” and buckle pavement.
With CU-Structural Soil®, urban trees get what they need: uncompacted soil with adequate moisture, drainage, aeration, and fertility. And needs of pavement are met, too: a load-bearing base and, if all goes well, a little shade from nearby trees.
The last time Cornell’s name went on designer dirt, it was the famous Cornell potting soil mixes and the recipe was distributed freely. This time CU-Structural Soil® is licensed by Amerq Inc., a small company in New City, N.Y. The primary reason for this is for quality control. The recipe for CU-Structural Soil® is simple, but it is easy to get it wrong. As is the protocol with other patented Cornell inventions, proceeds are shared among the university, the department of origin, and the inventor.
Whichever way technology is transferred—through free recipes or through a marketable product—the public and the plants come out ahead. (Roger Segelken)
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