Alternative substrates for potbedding plants

1
Alternative substrates for pot/bedding plants

• Susie Holmes
• ADAS Horticulture

2
The Major Alternatives

• Wood/forestry by-products
• Coir
• Green compost

3
Wood/forestry industry by-products

• Bark - pine and spruce
• Forestry by-products e.g. Sylvafibre, Pietal
• Sawdust
• Chipboard/furniture manufacture waste
• Recycled wood
• All need to be stabilised/composted before use

4
Coir fibre

• Must be from a reputable source
• Useful in propagation and for small modules
• Promotes good root development
• Used in blends as a low nutrient ingredient
• Non-indigenous, price may rise

5
Green compost

• Only high quality composts suitable
• Inherently high pH and K level
• Can have high chloride level
• High bulk density
• Useful slow release nutrient content
• Root pathogen suppression possible
• Needs diluting with low nutrient/low BD material

6
Blends for bedding/pot plants

• Reduced peat mixes - e.g. 20 - 70 other
  materials
• Woodfibre/bark (70/30) e.g. Sylvamix
• Sylvafibre/coir/loam (e.g. Petersfield Peat-free
  Supreme)
• Woodfibre/bark/green compost blends (e.g.
  Sinclair peat-free, Klasmann-Deilmann RT mix)
• Green compost/bark (e.g. Gem peat-free)

7
Management of peat alternatives

• Adapting irrigation is the key to success
• Some materials need more frequent watering
• Bark/wood wastes and coir need more N
• Nutrition needs to be reviewed
• Handling with automated systems needs examining
  e.g. flow into small modules

8
Further research needed

• Irrigation requirements - compatibility with
  different systems esp. capillary
• Fine-tuning of nutrient requirements
• Herbicide insecticide efficacy
• Compatibility with machinery
• Disease suppressive effects of green
  compost/woody materials
• Shelf-life