Basics on soilless growing media. Physical, chemical characteristics and other attributes

1. It all depends….
SOILLESS MIXES
Kevin Donnelly, CH
.

2. GROWING MEDIA
 Air
 Water
 Structure
 Nutrient Reservoir

3. THE IDEAL MIX
 It all depends….
 Fits your growing style
 Produces quality plants with limited
management
 Consistent/Predictable
 Cost effective

4. PHYSICAL PROPERTIES

5. MACRO VS. MICROPORES
30% Air
75% Water 45% Water
25% Solids 25% Solids

6. CAPILLARY ACTION IN MIX
 Important when sub irrigating containers
 Pores act as a straw and

7. ZONE OF SATURATION
 Amount mix will hold at the bottom

8. CONTAINER SIZE
 Size and Shape of container can effect water
air water relationships
 Look at the force of gravity
45% Air
25% Air
10% Air

9. BULK DENSITY/ COMPACTION
 Depending on how it is filled can impact air
water relationships
 Compact vs. lightly filed

10. SHRINK
 Settling after watering
 Component breakdown
 Out the bottom?
 Shrink from blending

11. WHY IT MATTERS
 Overwatering or under watering causes
issues
 Pick up method of checking watering status
 If I change the weight of your mix, you will mess
up
 Surface may dry up but not underneath
 Knock out pots to check

12. WETTING AGENT
 Aids in wetting up mix
 Peat is hydrophobic
 Helps with even watering,
 Not channeling down the sides of the pot
 A good idea for postharvest quality

13. CHEMICAL PROPERTIES

14. PH
 Will effect nutrient availability
 Fluctuates over the course of the crop
 The plant causes pH changes
 Alkalinity of your water is important
 May need to do acid injections
 Buffer capacity of your components
 Lime and Iron Sulfate

15. PH

16. EC
 AKA soluble salts
 Measure of salt content in solution
 Can be from good salts or bad
 Many use EC as indication of fertility
 Listed in dS/m or ppm (dS/m X 670)
 Dilution method matters!!

17. NUTRIENTS
 Minerals/non coated
 dolomite lime
 Iron Sulfate
 Controlled Release Fertilizers (CRF or SRF)
 Encapsulated NPK+
 Organic Fertilizers
 Often have low analysis and low availability
(predictable)

18. OTHER MEASURMENTS
 Organic Matter
 CEC
 C:N
 Weed Seed presence
 Wettability
 Moisture content

19. TESTING
 What do you test for
 How Often
 How do you test
 Interal testing
 External lab
 What do you do with that
information

20. SAMPLING
 How you sample may add bias to the test
 Area of pot
 Top 1/3rd
 Middle 1/3rd
 Bottom 1/3rd
 Random sample or targeted sample

21. TESTING FOR PHYSICAL PROPERTIES
 Air Porosity
 Field Method
 NCSU Porometer
 Sieve analysis

22. TESTING CHEMICAL
 In house
 EC
 pH
 External Lab
 Nutrients
 CEC
 Etc.

23. EC
 Method maters
 1:1
 2:1
 SME
 Pour Thru
 Many use it for managing fert
 If EC reading falls below X, then fertigate

24. PH TESTING
 Moving Target
 Can be adjusted
7
6.5
6
5.5
5
4.5
4
1 2 3 4 5 6 7 8 9

25. BIG POINT FOR ANY TESTING
 Don’t make major changes right after testing
starts to correct issues that may be normal
 Need historical values to see what is your
norm
 Plants don’t read test reports

26. BIOLOGICAL
 Mycorrhizae
 Benificial bacteria/fungi
 These can be incorporated into mix
 As well as some pesticides

27. Its all about logistics
COMPONENTS

28. AGGREGATES
 Perlite  Others
 Vermiculite  Lava
 Glass
 Sand
 Polystyrene
 Calcined clay
 Rockwool
 Oildri
 LWA

29. ORGANIC COMPONENTS
 Peat  “Composts”
 Landscape compost
 Sphagnum
 Manure compost
 Reed Sedge
 Biosolids
 Pine
 Worm Casting
 Rice
 Mushroom “Compost”
 Coir  Spent Mushroom
Substrate

30. NEW PRODUCTS
 Why we need them  Look for local
 Price  Cheap
 Availability
 Effective
 Quality
 Sustainability
 These are not
replacements

31. NEW FRONTIERS
 Whole Tree Substrate
 Corn Cobs
 Miscanthus
 Biochar

32. MANAGING RAW COMPONENTS
 These are natural
products
 They vary
 They change over time
How you manage them
maters