1. McGee, C.F., Gaffney, M. and Doyle, O.
Assessing the potential of commercially composted waste streams for suppressing root rot diseases in horticultural crops
McGee, C.F., Gaffney, M. and Doyle, O.

2. Background EU Landfill Directive
Markets needed for composted materials
Evidence of disease suppressive properties

3. Aims
To assess a range of commercially composted waste streams for disease suppressive potential
To determine if waste stream composition could be associated with disease suppressive ability
To determine if physico-chemical characteristics can be associated with disease suppressive potential

4. Characterisation and Methods
Pot based growth trials in glasshouse units
Fresh weight measurements
Composted materials characterised using CEN protocols for pH, EC and self heating
Three patho-systems investigated

5. Pathogens Oomycete and fungal
Identified by morphological characteristics of sporulating structures and molecularly on ITS sequences using universal primers
P. ultimum
P. erythroseptica
F. oxysporum

6. Pathosystems P. ultimum – Brassica pekinesis F. oxyspoum – Allium cepa
P. erythroseptica – Solanum lycospercium
Peat based inocula
Re-isolation between trials
Inoculation rates based on literature

7. Characteristics Compost Waste streams pH EC (mS.cm-1) Temp Δ (°C) A
Seafood processing waste (33.5%) green waste (66.5%)
7.92
4.48 B
Green waste (100%)
8.81
1.84
3.45 C
Biowaste (98%), animal manure (2%)
7.35
4.12
1.35 D
Seafood processing waste (100%)
6.57
4.96
0.25 E
Biowaste (53%), sewage sludge (45%), animal manure (2%)
8.35
0.33
10.8 F
Biowaste (100%)
6.88
4.65
0.45 G
Biowaste (66%), animal manure (33%)
9.04
1.40 H
Animal manure (66%), green waste (33%)
8.73
2.51
3.35 I
Biowaste (95%), sewage sludge (5%)
7.54
0.83 J
Sewage sludge (60%) and animal manure (40%)
7.29
1.80 K
7.72
1.44 L
Biowaste (50%), animal manure (50%)
8.43
1.38 m
Manure (42.5%), green waste (2.5%), seaweed (50%)
6.82
37.15 n
Manure (95%), green waste (5%)
8.70
5.03
40.7 o
Manure (90%), green waste (10%)
6.33
8.64

8. PCA
Compost Composition
Physico-chemical characteristics

9. Suppression
Compost
P. ultimum
P. erythroseptica
F. oxysporum a
74.9
79.5
90.7 b
130
108.1
47.9 c
62.5
139.5
128.6 d 49
45.7*
56.7 e 60
13.1**
103.2 f 51
31.4**
49.7* g
74.2
98.3
88.5 h
62.2
188.5 i
33.9*
53.8
183.5 j
124.1
104
156.3 k
30.5*
87.5 l
69.5
93.2
106.3
Average
68.5 ± 30.8
77.1 ± 36.6
107.3 ± 48.3
Disease severity in pot based growth trials expressed as percentage of inoculated control. Asterisks (*) represent significance, * = P ≤ 0.05 – 0.001, ** = P < 0.001

10. Conclusions High variability seen in commercial products
Trends indicate biowaste associated with suppressive capacity
Salinity a problem for inclusion rates at 20% or more
Engineering composts suppressive ability a more realistic option