Introducing ……...

Slate waste

EU Life-Environment funded project:

Sustainable post-industrial land restoration and re-creation of high biodiversity natural habitats

Partners: University of Wales, Bangor; Alfred McAlpine Slate; Slate Ecology Co.,

Pizarras- Villar del Rey

Output: To produce a science-based guide to Best Practice for achieving the restoration of self-sustaining, semi-natural ecosystems of high conservation value

Scope of the project

• Nutrient and water delivery systems

• Plant responses

• Litter decomposition and soil formation

• Invertebrate, detritivore and bird biodiversity

• Socio-economic impacts

• GIS overlays of environmental variables

Soil functioning in natural and restored systems on slate waste

Julie Williamson1, Davey Jones1, Richard Bardgett2, Phil Hobbs3, Ed Rowe1, Mark Nason1 & John Healey1.1 University of Wales, Bangor, 2 University of Lancaster, 3 IGER.

Rationale and Hypotheses• typically, quarry sites lack topsoil

H.1 theoretical C:N considerations can be used to design substrates from organic wastes for nutrient delivery

• nutrient cycling needs a ‘kick start’

H.2 organic matter increases nutrient cycling capacity

• need to develop soil biochemical indices that predict longer-term above-ground success

H.3 organic amendments create a substrate biochemically comparable to that of naturally established vegetation

Method used for tree planting

Slates arranged tocollect rainfall

1-year oldtransplant

Soil amendments in 3 L pocket, depth 15 cm

Free-drainingcoarse slate waste

1mRoots moving towards fines

Water-holding fines

Design of tree establishment trial

3 water-holding treatments

None Boulder clay Polyacrylamide gel

3 nutrient supply treatments

None *Sewage-paper NPK (15:10:10) mix slow release

* mixed to a target C:N of 15-20 and to deliver mineral N at the same rate as NPK in Year 1

Materials used for tree establishment

Water factorkg.kg-1

Total C%

Total N%

Olsen Pmg.kg-1

GrossC:N

Sewage-paper mix

3.5 29.2 2.01 1.05 15

Selected nutrient concentrations of the organic amendment.

Target application rates to planting pocket kg.N ha-1

NPK 550 sewage-paper 4000

Results: substrate Mineral-N content (mg N.kg-1) over 3 samplings (1, 7, 13 months)

Fertiliser treatment P value

No fertiliser Sewage-paper mix

NPK

4.1 a 27 b 33 b < 0.001

Results: soil microbial biomass (mg N.kg-1) and basal respiration (mg C.kg-1.h-1) at 13 months

Fertiliser treatment P value

Nofertiliser

Sewage-paper mix

NPK

Microbial N 21 a 135 b 29 a < 0.001

Respiration 0.40 a 3.29 b 0.44 a < 0.001

Results: summary of soil N pool sizes at 13 months

mg N.kg-1 No fertiliser Sewage-paper mix

NPK

Total N (%) 0.056 a 0.30 b 0.061a

Mineral N 0.7 a 3.4 a 23.8 b

*PMN 10 a 86 b 25 a

Biomass N 21 a 135 b 21 a

*PMN+Mineral N 11a 89 c 49 b

*PMN is potentially mineralisable N

Results: comparing soil quality indices of naturally established and planted birch.

Microbial Nmg.kg-1

Respirationmg CO2C.g-1.h-1

Natural birch 137 b 2.63 b

Planted: no fertiliser 21 a 0.40 a

Planted: sewage/paper 135 b 3.29 b

Planted: NPK 21 a 0.44 a

Results: comparing soil quality indices of naturally established and planted birch.

Microbialquotient

Respiratoryquotient

MicrobialC:N

mean range mean range mean range

Natural birch(n = 24)

3.1 1.3-4.4 0.3 0.2-1.0 11 5-14

Planted birch(n = 27)

2.5 0.3-8.6 3.5 0.3-5.9 3 1-5

Results: Soil microbial PLFA profiles of natural and planted vegetation.

Proportion (% mol) of Gram+ve bacterial PLFA to total.

0

20

40

60

80

S S S

< Natural >< Planted >

Results: Soil microbial PLFA profiles of natural and planted vegetation.

Ratio of fungal-to-bacterial PLFA.

< Natural >< Planted >

0

0.1

0.2

0.3 Ratio of fungal to bacterial PLFA

Results: Soil microbial PLFA variation in natural and planted vegetation.

210-1-2

2

1

0

-1

-2

axis 1

axis

2 p

p(s)

p

p

p(s)

p

p p(s)

p

n

nn

n(bare)

nn

n

Plot of coordinates derived from detrended correspondence analysis (Canoco)

Conclusions

H.1 theoretical C:N considerations can be used to design substrates from organic wastes for nutrient delivery

Yes; soil mineral N concentrations during the first 13 months in the NPK treatment were matched by the sewage-paper mix treatment

H.2 organic matter increases nutrient cycling capacity

Yes; as evidenced by increases in microbial biomass, respiration and potentially mineralisable N, relative to other treatments

Conclusions cont’d

H.3 organic amendments create a substrate biochemically comparable to that of naturally established vegetation

Sewage-paper resulted in soil microbial biomass and respiration rate comparable to those in natural systems

But, microbial composition differed markedly, viz:

Planted systems had:

• greater proportion of bacterial PLFA

• lower microbial C:N ratio

• higher respiratory quotient