Friday Follies: Breakfast Loaf & Soil Biology

This zucchini and olive breakfast loaf is amazing, and dead easy. While zucchini is used as the base of the loaf, it doesn’t taste at all like zucchini or your average (sweet) zucchini bread. It is savory amazing-ness. Go make it immediately.

And now to the main part of today’s program, a technical memorandum from Peter MacDonagh, ASLA, ISA, RHS, CSLA (phew, lotta acronyms!) on issues related to soil biology. This is particularly relevant for Silva Cell projects where the trees may not be planted for up to two years after the system installation has occurred.

Based on my experience and a search of peer reviewed literature I can find no issue with soil biology decay under pavement within the described time span. In this instance, trees would not be placed into the Silva Cell chambers for a period of 2 years. The macropore rich soils inside the Silva Cells will continue to “live” under the pavement for the following reasons:

In horticultural parlance, soils become “dead” in extreme anaerobic environments. It is a biological fact that there are numerous anaerobic bacteria and viruses that survive even in low oxygen soil environments. However, these are “dead” soils from a horticultural standpoint. Typically, long periods of inundation (months) causes soils to “die,” again this is from a horticultural point of view.

The key to “living” soils is the free movement of water and oxygen through the soil column. This oxygen-rich environment is made possible by macropores. These soils are ideally comprised of: 50% mineral; 25% water; 25% air.

Silva Cell specifications call for these macropore rich soils to be installed inside the frames of the system. Beneath the deck of the Silva Cells is a 1 inch to 3 inch (2.5 to 7.5 cms) air gap. This air volume allows free exchange of oxygen through the soil column.

The primary microorganisms of concern for “living” soils are Mycorrhizae, filamentous fungi primarily of the Glomus genus. Of all the biological associations in the world of trees, Mycorrhizae provide the greatest and most dramatic benefit to trees for water and nutrient uptake (USNFS; Amaranthus; Shigo).

The largest supplier of laboratory cultured Mycorrhizae in the world has placed a minimum 2 year shelf life on its shipped Mycorrhizae product inside sealed plastic bags at 80 degrees  F/26.7 degrees C, stored out of direct sunlight (Amaranthus et al).

The growing conditions under the pavement will not reach those extremes. Therefore the macropore rich soils inside the Silva Cells with air gaps under the decks will continue to keep the soils “alive” for a minimum of 2 years.

Peter MacDonagh, Director of Science + Design, Deep Root Urban Solutions & The Kestrel Design Group.

(Image: The Kitchn)

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