Jardí Botànic de Barcelona
cultivate the soils after the passage of much heavy
machinery.
The standard correction applied to the whole site
before inauguration consisted of the addition of a
15cm top layer consisting of 55 per cent coarse
gravel, 20 per cent clay, 10 per cent mud and 15 per
cent organic matter. Oversized tree pits (more than
twice the root area) were used in order to improve
planting conditions; these were backfilled with a
mixture of 50 per cent coarse sand, 30–40 per cent
plant-based organic matter, and 10–20 per cent
animal manure.
Where more acidic conditions were required a
standard specification was an 80cm–1m-deep plan-
ting bed, consisting of 10cm of drainage quarry
rubble (30–70mm), 50–60cm of coarse sand, 10cm
of sieved coarse sand, 20cm of a mix of 75 per
cent sieved coarse sand and 25 per cent organic
matter. After the soil improvement process, a con-
ventional tree and shrub planting process was fol-
lowed, together with the installation of an irrigation
system.
Mulching and soft paving scheme
After the opening, the aim was to get closer to the
character of the original landscapes, while rational-
ising maintenance, especially in those phytoepi-
sodes which had just been planted or where the
percentage of soil covered by plants was low. Thus,
a mulching and soft-paving scheme was conceived.
The practical criterion was to search for a functional
alternative to the original landscape cover. Different
solutions are being tested at the moment:Sieved coarse sand (beige in the scheme)
is used for the driest phytoepisodes with
low plant coverage, as well as for dressing
many of the areas of an acidic nature, and for
developing scrubland phytoepisodes that will
eventually be totally covered with vegetation.
The sand is spread in a 10–15cm layer on top
of a geotextile. In the driest phytoepisodes the
mulch is 100 per cent coarse sand, while in the
rest 25 per cent organic matter is added.
Woody prunings (sky blue in the scheme) are
used in woodland phytoepisodes with little
understorey. The prunings consist of branches,
mostly from conifers and up to 20cm long,
which have not been composted. They are laid
in an 8–15cm layer.
Volcanic gravel (purple in the scheme) is used
in the Canary Islands volcanic phytoepisodes.
Two textures are used: a red 10–15mm mix and
a bigger 20–25mm black one.
Pine needles are used in the Canary Islands
pinewoods phytoepisodes, just as they occur
in nature. Fallen pine needles are simply left on
the ground.•
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7.28
Acidic soil improvement at South Africa’s Fynbos