1. Chemistry of plug production
Neil Bragg
Product Development Director
Bulrush Horticulture Ltd

2. Issues to consider: Physical size of the plug unit Water quality
Chemical properties of ingredients
Practical fertigation
Monitoring for quality,

3. Different size of plug units
350’s to 28’s – volume of units
Tray
Vol mls
350
4.7
230
7.5 40
87.5 28
285

4. Water quality and the issues surrounding:
Most important characteristic:
ALKALINITY –degree of temporary hardness,
Soft water – rainwater collection – ppm Alkalinity
Issues Calcium and Magnesium supplies
Medium Hard water ppm Alkalinity
May be worth ‘softening’ water via acid injection
Choice of acids, Nitric and for lower levels of hardness citric acid
Hard water – ppm Alkalinity
Acid treatment needed to release Calcium and Magnesium, avoid
Increasing pH and hence lock-up of elements such as Iron (Fe).

5. Chemical properties of ingredients:
Ref: Technical monograph: Growing media laboratory methods, ADAS – ISBN:
Moving towards new materials we need an understanding of things such as the CEC of materials:

6. Issues of moving away from peat
pH control in relation to spp:
Petunia vs Geranium
Supply of Calcium and Magnesium
Other sources, Gypsum & Epsom salts
Leaching potential
CP095 Fellowship work
Water holding capacity
Ease of filling plug trays

7. Feeding to achieve optimal growth:
Koranski – favoured the stages of growth approach
For ageratum
Stage 1, 2-3 days fertiliser 50ppm
Stage 2, 7 days fertiliser 50ppm
Stage 3, 14 days fertiliser 150ppm

8. Example taken from Plug and transplant production – Styer & Koranski

9. Issue of achieving the N inputs
Feed containing 150mg/l N
How much is actually applied per watering?
Might be 5mls –
Equivalent to : 0.75 mg N applied??????? Once or twice a week???

10. Monitoring of substrates in plugs
Squeeze tests
Saturated paste
Lab 2:1 extraction
Probes
Interpreting values- building the picture