It all depends….

SOILLESS MIXES

Kevin Donnelly, CH

.

GROWING MEDIA

Air

Water

Structure

Nutrient Reservoir

THE IDEAL MIX

It all depends….

Fits your growing style

Produces quality plants with limited

management

Consistent/Predictable

Cost effective

PHYSICAL PROPERTIES

MACRO VS. MICROPORES

25% Solids

75% Water

25% Solids

45% Water

30% Air

CAPILLARY ACTION IN MIX

Important when sub irrigating containers

Pores act as a straw and

ZONE OF SATURATION

Amount mix will hold at the bottom

CONTAINER SIZE

Size and Shape of container can effect water

air water relationships

Look at the force of gravity45% Air

25% Air

10% Air

BULK DENSITY/ COMPACTION

Depending on how it is filled can impact air

water relationships

Compact vs. lightly filed

SHRINK

Settling after watering

Component breakdown

Out the bottom?

Shrink from blending

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

May not be watering enough or evenly

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

CHEMICAL PROPERTIES

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

PH

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!!

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)

OTHER MEASURMENTS

Organic Matter

CEC

C:N

Weed Seed presence

Wettability

Moisture content

TESTING

What do you test for

How Often

How do you test

Interal testing

External lab

What do you do with that

information

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

TESTING FOR PHYSICAL PROPERTIES

Air Porosity

Field Method

NCSU Porometer

Sieve analysis

TESTING CHEMICAL

In house

EC

pH

External Lab

Nutrients

CEC

Etc.

EC

Method maters

1:1

2:1

SME

Pour Thru

Many use it for managing fert

If EC reading falls below X, then fertigate

PH TESTING

Moving Target

Can be adjusted

4

4.5

5

5.5

6

6.5

7

1 2 3 4 5 6 7 8 9

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

BIOLOGICAL

Mycorrhizae

Benificial bacteria/fungi

These can be incorporated into mix

As well as some pesticides

COMPONENTS

Its all about logistics

AGGREGATES

Perlite

Vermiculite

Sand

Calcined clay

Oildri

LWA

Others

Lava

Glass

Polystyrene

Rockwool

ORGANIC COMPONENTS

Peat

Sphagnum

Reed Sedge

Pine

Rice

Coir

“Composts”

Landscape compost

Manure compost

Biosolids

Worm Casting

Mushroom “Compost”

Spent Mushroom

Substrate

NEW PRODUCTS

Why we need them

Price

Availability

Quality

Sustainability

These are not

replacements

Look for local

Cheap

Effective

NEW FRONTIERS

Whole Tree Substrate

Corn Cobs

Miscanthus

Biochar

MANAGING RAW COMPONENTS

These are natural

products

They vary

They change over time

How you manage them

maters