1. Transition to responsibly sourced growing media use within UK horticulture (CP138)
Dr Barry Mulholland (ADAS), Prof. Keith Waldron (QIB), Andrew Watson (QIB), Graham Moates (QIB), Chloe Whiteside (ADAS), Julian Davies (STC), Dr Sonia Newman (ADAS) and Ryan Hickinbotham (ADAS)

2. CP138 aims (5 year project 2015-2019)
To construct a model that will produce the desired mixes at least cost.
To evaluate responsibly sourced growing media blends as alternatives to peat in commercial crop production systems.
By on-site demonstration and effective communication of the scientific evidence base, increase grower confidence to facilitate the uptake of responsibly sourced growing media for commercial horticulture.

3. RSGM Growing media raw materials Wood fibre Peat Coir Green compost
Bark

4. Commercialisation of strategic research (UK and US patents) for
controlled composting processes B 4 3 2 A C 6
Air Porosity
Dry Bulk
Density
Moisture
Retention 5
Peat-based
collection
Very immature
Composts
Plant structure
relatively
undegraded
Completely mature
Composts with little or no structure 1
Arrow represents
direction of loss
of structure
during composting
Waldron et al. (2013). Retaining cell wall structure in producing quality composts to replace peat as a growing media. Acta Hortic. 1013,

5. Selected physical variables (centroid approach)
GREEN COMPOST
Db (g cm-3)
(Mulholland et al. (2016) Technical monograph: Growing Media Laboratory Methods. ©ADAS, ISBN , 24 pp.

6. Comparing measured versus predicted (geometric algorithm) values for blended growing media physical properties
calculated
measured

7. Geometric axial augmented simplex centroid approach for prototype blend selection
Db (g cm-3)
GREEN COMPOST

8. Year (Growing season activity)
On-site grower trials and Knowledge Exchange
Sector
Year (Growing season activity)
1 (2015)
2 (2016)
3 (2017)
4 (2018)
5 (2019)
Total
Mechanisation
SITE 1 3 FV
SITE 2
SITE 3
HNS (p)
SITE 4
SITE 6 2
HNS (m)
SITE 5
SITE 7 4 M PE
SITE 8
SITE 9
PO (p)
SITE 10
SITE 12
PO (m)
SITE 11
SITE 13
SF (p)
SITE 14
SF (m)
SITE 15 TF
SITE 16
Total on site trial / KT event No. 8 6 30

9. Apple trees – experimental
Bramley apple - 12 weeks growth
No significant difference in branch extension

10. Apple trees – on nursery
Christmas Orange Pippin - 12 weeks growth
Significant difference in branch extension (p = 0.005)
Prototype blend 2 has significantly higher growth

11. Herbs - Chive

12. Current proprietary peat, peat reduced and peat free (baseline) and prototype blend comparison
Prototype blends
Db (g cm-3)
Trial 1
VEGETABLES 2
STRAWBERRY 3
HERBS 4
Hardy Nursery Stock 5
BEDDING PROP 6
BEDDING TRANS

13. Next generation prototype blend development
GREEN COMPOST
PEAT
COIR
BARK
AFP (%)
WOOD FIBRE
Db (g cm-3)
Raw Material type 1
COIR 2
BARK 3
GREEN COMPOST 4
WOOD FIBRE 5
PEAT

14. Summary of findings
RSGM in either raw or mixed form can be located as a point in the three- dimensional space specified by three physical parameters AW, Db and AFP.
Values of AW, Db and AFP in mixes can be calculated from those of the raw material constituents.
Prototype mixes that come close to the “peat centroid” have been developed and tested under a range of nutrient and water regimes representative of commercial practice. The process is iterative.
RSGM physical properties have also been related to commercial plant quality data to develop a model that can predict plant performance from growing media raw material.
Current work is identifying the performance of mixes that are not necessarily close to the peat “centroid”; to build a better predictive model.
The model will be an effective screening tool to identify “best blends, least cost“.

15. Acknowledgements
Generous support of the growing media and mechanisation industries.
Access to grower sites and working with the growers to seek robust and high quality data to progress the peat alternative challenge for Horticulture in England.
Unstinting support of colleagues in pursuit of excellence in experimental and commercial testing so that the industry can observe the development of the project in practice.
The important contribution of experts to workshop delivery and knowledge exchange for multiple aspects of growing media / root-zone management.
Thank you for listening - any questions?