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Marie-Curie IAPP ‘Green Roof Systems’ Project

The Green Roof Research Conference 18-19 March 2013, Sheffield

Substrate physical properties and potential amendments Dr. Tobias Emilsson1, Ralf Walker2 1

Senior Researcher, ZinCo GmbH, tobias.emilsson@zinco-greenroof.com 2 Project Leader, ZinCo GmbH, ralf.walker@zinco-greenroof.com

Introduction The establishment of the green roof vegetation is crucial to system performance in respect to e.g. stormwater reduction, biological diversity and aesthetic qualities. The main problem during the establishment phase is drought which can cause almost complete failure of the vegetation. Re-establishment of failing vegetation or improving establishment through irrigation is related to increased cost of installation which means that there is a strong drive to develop substrates that can support the newly established vegetation with water for an extended period of time and thereby increasing survival. We have been investigating the effect of different types of amendments on water storage and maximum water holding capacity in crushed brick based green roof substrates. The main focus has been direct towards finding amended substrates that improve survival and plant performance during a drought cycle.

Overview of Methodology Our investigation started with a broad investigated of available substrate amendments from which a number of interesting and different amendments were selected. Our analysis have been primarily focused on measurements as defined by FLL, development of soil moisture retention curves and plant based drought survival tests.

Figure 1 – Substrates have been investigated through 3 different methodologies: A) Physical tests as defined by FLL. B) Plant based drought survival test in controlled climate, and C) Pressure extraction for determination of available water content and soil moisture retention curves.


Marie-Curie IAPP ‘Green Roof Systems’ Project

The Green Roof Research Conference 18-19 March 2013, Sheffield

Key Findings Most of the investigated amendments were found to have a clear effect on water holding capacity of crushed brick based substrates. Increasing the amendment level increased the water holding capacity. We also discovered that different amendments did influence the plant performance even when substrates were designed to have the same 35 % V/V maximum water holding capacity. Thus, the characters of the individual amendment did influence plant performance.

Figure 2 – Maximum water holding capacity as defined by FLL for crushed brick based substrates amended with 5 different types of organic material in different levels. Substratetype: Gel Bromus

Leucanthemum

Sedum

5 4

Gel1

3

Plant rating (0-5)

2

day 0 7 14 21 28 35 49

1 0 5 4

Gel2

3 2 1 0 0

10

20

30

40

50 0

10

20

30

40

50 0

10

20

30

40

50

Water content % (V/V)

Figure 3 – Plant performance (visually rated 0-5) for two different substrates amended with hydrogel and planted with Bromus, Leucanthemum and Sedum during a 7 week drought experiment.

Substrate physical properties and potential amendments - Tobias Emilsson  

The establishment of the green roof vegetation is crucial to system performance in respect to e.g. stormwater reduction, biological diversit...

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