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Title: Physical Characteristics of

1
Substrate Technology, Water and Mineral Nutrition
in Protected Agriculture Workshop
Day 1 Topic 2
Physical Characteristics of Soilless Substrates
Andrew G. Ristvey Extension Specialist
Commercial Horticulture
University of Maryland Extension Wye Research
and Education Center College of Agriculture and
Natural Resources University of Maryland
2
Smarter Substrate Management

Objectives for this topic include
Review soilless substrate physical properties
Relate those factors to air and water
availability
Evaluations for physical properties

3
Soils vs Soilless Substrates
What are the important physical differences
between soils and soilless substrates?
Parent materials or components
Particle size
Porosity
Air and water availability
4
Particle Size
Soils

Soilless Substrates
Composition
Particle Size Pore

Texture
Structure

5
Soilless Substrates Physical Properties

Three Phases of Growing Media by volume

Solid (matrix) 33 to 50
Liquid (water) 15 to 45
45 Solid (matrix)
Gas (air) 10 to 40
Water Air Total Pore Space
15 - 45 Water
10 - 40 Air
Matrix Component Porosity
determines the ratio between
6
Variability of Components

Peat Moss
Pine bark
Perlite
Coir
Rice Hulls
Shredded palm leaves
and other organics
Sand
Gravel
Vermiculite

Highly Variable
Physical properties
Very porous
Leach very easily
Various combinations
Plant Available Water
the volume of water that plants can retrieve

7
Component Structure
(Handreck Black, 1994)
8
Typical Substrates Utilized in Costa Rica
9
Porosity Air and Water Availability

Physical Properties

Particle Size and Composition Their affect on

Air-Filled Porosity (AFP)
Water Holding Capacity (WHC)

AFP - air in the substrate after irrigation /
drainage
WHC water in the substrate after irrigation /
drainage

10
Pores

When we buy substrate---we are buying pores!
What else can affect substrate AFP and WHC?
Handling
Watering
Age
Container geometry
Potting
- do not compress substrate
- water the plant in

11
Components Affect AFP and WHC

Porosity
Macropores ? Water drain
through freely
(lt 4mm)
Mesopores ? Water at CC
(1 to 0.5mm)
Micropores ? Water might
work as
buffer
(0.5 to 0.03mm)
Ultramicropores ? Water held
beyond 1.5 Mpa
(lt0.01mm)

Drzal et al. (1999)
12
Components Affect AFP and WHC

Particle size affects WHC and AFP

Capillary action

water tension - water is attracted
to surfaces with a force large
enough to support a relatively
large mass of water against the
pull' of gravity

the smaller the particle, the
more firm the hold

13
Components Affect AFP and WHC

Physical Properties Pore Size

Pore size affects WHC and AFP

14
Soilless Substrates
Important Attributes of Soilless Media

Recommended physical characteristic values for
soilless
substrates, after irrigation and drainage are (
volume)
Air-Filled Porosity - 10 to 30 or 20 to 35
(field test)
Water Holding Capacity - 45 to 65
Available water content - 25 to 35
Unavailable water content - 25 to 35
Note A substrate with many coarse particles has
a large air space
and a relatively low water holding
capacity.

15
Field Test for AFP

W1 Saturated container media
W2 Drained container (several hours later)
W3 Volume of Substrate
W4 Weight of Container
W5 Weight of Dry Media

Saturation
W1
W2
AFP
X 100
AFP
W3
W4
Total Volume
16
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Substrate Technology, Water and Mineral Nutrition
in Protected Agriculture Workshop
Day 1 Topic 3
Substrate Management
Andrew G. Ristvey Extension Specialist
Commercial Horticulture
University of Maryland Extension Wye Research
and Education Center College of Agriculture and
Natural Resources University of Maryland
18
Smarter Substrate Management

Objectives for this topic include
Composting and aging
Storage of substrates
Handling of substrates

19
Composting and Aging
Composting is a biological process where complex
organic material is degraded into more basic
organic components at a rate faster than
decomposition would occur naturally. Aerobic
Composting is a thermophilic (generating heat)
process Aging is not composting, because there
is no heat generation
20
Composting and Aging

The process of efficient composting requires
several ingredients.
The basic recipe
A source of organic material
Microorganisms
CN ratio of more than 301 this may mean
the addition of
a nitrogen or carbon source
Proper moisture levels 45 to 60 by weight
Oxygen
pH stabilizer, if needed

21
Composting and Aging
Composting Chemistry The CN Ratio
Materials High in Carbon C/N
Senesced leaves 30-801
straw 40-1001
wood chips or sawdust 100-5001
bark 100-1301
mixed paper 150-2001
newspaper or corrugated cardboard 5601
Materials High in Nitrogen CN
vegetable scraps 15-201
coffee grounds 201
grass clippings 15-251
manure 5-251
22
Composting and Aging

The result of efficient aerobic composting is .
Generation of Heat 55 Co
CN Ratio of between 10 and 15 1
Degradation of organic material and increase
Cation Exchange Capacity

23
Composting and Aging
Microorganisms
24
Composting and Aging
The Aerobic Cycle
http//www.theteggroup.plc.uk/technical_library/mi
crobiology_of_invessel_composting
25
Composting and Aging

Cellulose and Lignin
Why some substrates degrade
faster than others
Cellulose is a sugar
Lignin is a more
complicated molecule
and more difficult
to degrade

26
Composting and Aging

When it goes wrong
Compounds like alcohols and methane are developed
in anaerobic composting.
Weed and pathogens are not destroyed

27
Adding Compost to Growing Media

Consistency can you assure?
Well/properly composted
Water Holding capacity Pore Space?
Nutrient availability
what is in compost?
adjust your nutrient management plan?

28
Adding Compost to Growing Media

First, analyze your compost
All macro and micro nutrients
How much should be added?
Base your addition on nutrients, WHC AFP and EC
Usually no more than 20
Check your WHC and AFP

29
Smarter Substrate Management

There are three lines of defense against plant
diseases
To prevent pathogens from entering the
production systems
Create cultural conditions that work for plant
growth and
against disease development
Correctly and timely treat disease problems
that do arise

But first Prevention! is crucial to successful
plant health management
30
Storage of Substrates
31
Storage of Substrates

Storage high and dry?
Potting
- do not compress substrate
- water the plant into pot
What else?
Handling
Watering
Age

32
Storage of Substrates
33
Practical Examination for Substrates

Capillary Force practical experiment
Particle Distribution Analysis
Field Porosity and water holding capacity tests
Question
Does particle size affect AFP and WHC?

34
Substrate Re-use and handling
35
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36
Substrate Technology, Water and Mineral Nutrition
in Protected Agriculture Workshop
Day 2 Topic 4
Irrigation in Protected Environments Systems
Audit
Andrew G. Ristvey Extension Specialist
Commercial Horticulture
University of Maryland Extension Wye Research
and Education Center College of Agriculture and
Natural Resources University of Maryland
37
Overhead Irrigation Systems
The pros and cons of overhead irrigation systems.

Pros
Easy management
Lower labor costs
Less infrastructure

Cons
Efficiency low - depending
Larger volumes needed
Higher pressures needed

38
Micro Irrigation Systems
The pros and cons of microirrigation systems.

Cons
Greater management
Higher costs more specialized
equipment needed
Potential Higher labor costs

Pros
Higher Efficiency
Less volume needed
Lower pressures
Less waste

39
Irrigation Audits
Summary Is your irrigation system working
properly? First, do an inspection repair
problems. Second, check pressures and flow
rates. Third, do a test for uniform
application. Decide on changes to improve
system and water wisley.
40
Uniform Water Application?
Applying water uniformly should be goal 1,
particularly for container crops Question -
Where are your dry spots after irrigation? If
none, do you knowingly overwater some plants to
adequately water other plants? How do I check my
irrigation system?
41
System Audit Procedure
First, inspect for problems and repair them. 1.
Damaged pipelines and risers 2. Damaged,
clogged, worn, or broken nozzles or drip tubes.
42
System Audit Procedure
Second, check pressure and flow rate. 1. What
were the pressures and flow rates of the system
when new? 2. Check pressure at pump, beginning
and end of laterals, and before and after
filters. 3. Check the nozzles for wear and flow
rate. Check drip tubes for clogging.
43
Pressure Check
Installed or Portable Pressure Gauges
44
Pressure Check
Filter
Pump
Pressure Gauge
Laterals drip or sprinkler
45
Pressure variation in a Lateral
For good design, pressure variation from one end
of a lateral to the other should not exceed /-
10 percent of the average lateral design
pressure. Actual variation in lateral is 20.
Average of 50 psi
45 psi
55 psi
46
Pressure affects Application Pattern
Correct operating pressure is best! Pressure too
high or too low causes distortion of application
pattern.
47
Nozzle Flow Rate
Use a bottle or bucket to catch the water
discharged from the nozzle for one
minute. Measure the volume of water caught.
Convert to gal/min. as in nozzle chart. Measure
nozzle pressure, if possible.
48
Nozzle Flow Rate
RainBird 14DH
Nozzle (new) specs for water discharge at a given
pressure.
49
Nozzle Flow Rate
RainBird 14DH
Note changes in gpm for changes in PSI.
50
Nozzle Wear Check
Use drill bit to check size carefully.
51
Nozzle Wear
RainBird 14DH
Note changes in gpm radius for changes in Size.
Wear changes demand on the pump.
52
Nozzle Pressure Flow Rate
Lets recap the last few slides We checked
nozzle wear, pressure and flow rate. From the
nozzle chart we saw that a different pressure
resulted in a different discharge and wetted
radius. Differences mean non-uniformity!
53
Nozzle Pressure Flow Rate
Lets recap the last few slides We checked
nozzle wear, pressure and flow rate. From the
nozzle chart we saw that a different pressure
resulted in a different discharge and wetted
radius. Differences mean non-uniformity!
54
Application Uniformity Check
The next step is to check on the application
uniformity of your system. This process uses a
grid pattern of water catch cans to collect
water. A regular pattern of cans is placed on
the ground in the irrigated area.
55
Application Uniformity Check
Catch can top left Calibrated measuring
container bottom left/ top right
56
Application Uniformity Check
57
www.iaef.org
Audit Kit
Irrigation Association Education Foundation
58
www.iaef.org
Audit Kit
http//www.iaef.org/Files/Combined_Module_Order_Fo
rm.pdf
59
Application Uniformity Check
Catch cans - use 16 or more.
60
Do audit to sample application uniformity several
places.
61
Application Uniformity Check
62
Application Uniformity Check
Irrigation Lateral
Catch cans
Production Bed Hoop House
Must run all laterals that cover catch area.
63
Lower Quarter Distribution Uniformity, DULQ
Sketch of laterals and sprinklers. Show catch
cans and amounts of water.
List in descending order. Mark smallest quarter.
Average of total and smallest 1/4 .
Divide Average of ¼ by Average of total x 100
64
Readings (use 16, 20, 24 or more) 0.32 0.34 0.32
0.34 0.30 0.28 0.25 0.30 0.33 0.30 0.27 0.33 0.36
0.24 0.31 0.37 Total of all 4.96 Average All
0.31 Total small 1/4 1.04Average 1/4
0.26 DULQ 0.26 / 0.31 x 100 84
65
Doing the Math easy!
We calculate the Lower Quarter Distribution
Uniformity, DULQ DULQ Avg of smaller 1/4
readings / Avg of all readings x 100 Tells us
how close the lowest (dry) readings are to all
readings. Less than 70-75 percent is not so good.
66
Summary
Correct pressure and nozzle/emitter flow rates
are important factors in overall uniformity of a
system. The Lower Quarter Uniformity
Distribution gives us a measure of the uniformity
of application. Check out your system soon.
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Substrate Technology, Water and Mineral Nutrition
in Protected Agriculture Workshop
Day 2 Topic 5
Irrigation in Protected Environments Plant/Substra
te Relations
Andrew G. Ristvey Extension Specialist
Commercial Horticulture
University of Maryland Extension Wye Research
and Education Center College of Agriculture and
Natural Resources University of Maryland
72
Smarter Irrigation Management

Manage irrigation and substrate water content

Are we over-watering? Water logging will
increase the incidence of disease

Water-use efficiency research at UGA showed
that during a 6 week trial, Vinca
(Catharanthus
roseus) could be grown with liter of water
without reduction in mass or quality

Why dont we use soil in containers?
Key reason too many fine particles, which
leads to waterlogging
Also, bottom of container creates a barrier to
drainage resulting in a perched
water table
The smaller the particle size, the higher the
perched table
Soilless substrates degrade in time and
act like soils

74
Container Size and Water Holding Capacity
Given the same substrate
Given the same volume
Moisture/air gradient capillary action
Squat containers hold more water
75
AFP and WHC based on Container Size
Water
Solid
Air
Adapted from A Growers Guide to Water, Media,
Nutrition for Greenhouse Crops, Ed. David Wm.
Reed, 1996.
76
Plant Available Water

Soils and substrates have the ability to hold
and release water
Some water is available for the plants
Some water is not available for the plants
even though the substrate or soil may seem moist
Why?
Recall our lesson about particle size and water
attraction

77
Plant Available Water
78
Plant Available Water

Soils and substrates have the ability to hold
and release water
Some water is available for the plants
Some water is not available for the plants
Even though the substrate or soil may seem moist
Why?
Recall our lesson about particle size water
attraction
Plant Available Water is the water that held by
the soil or substrate
Divided into
Easily Available Water and Water Buffer
Capacity

79
Plant Available Water
(Handreck Black, 1994)
80
Water
Easily Available
Buffer capacity
Readily available water
(Handreck Black, 1994)
7 kPa 1 PSI
81
Finding Plant Available Water

Desorption curves generated using a custom-built
desorption table using 5 and 20cm long Ech2O
capacitance sensors.

Ten columns were
simultaneously
desorbed for each
substrate (n30).

82
Finding Plant Available Water

Each column was packed by
slowly adding and settling the
substrate with water
Each column had a
capacitance probe sealed into
the top polycarbonate lid,
positioned centrally and
vertically down the column
Once sealed, each column was slowly hydrated over
6 hours to gradually force the interstitial air
out of the substrate

83
Finding Plant Available Water

Positive gas pressure was incrementally applied
at 1, 2, 4, 6, 8, 10, 20, 40, 60, 80 and 100
kPa

The volume of water expressed
at each pressure increment was
measured for each column

84
Results Physical Properties (5cm columns)
100 Perlite 80 Pine Bark 20 Peat 100 Coir 100 Pine Bark 80 Peat 20 Perlite
Pressure (kPa) Distribution of Water () Distribution of Water () Distribution of Water () Distribution of Water () Distribution of Water ()
EAW (1 to 5) 36.0 40.0 32.6 34.6 43.7
WBC (5 to 10) 1.2 7.0 2.1 2.2 13.1
PUW ( gt10 ) 62.8 53.0 65.3 63.2 34.1
Total volume of the 5-cm column 722 mL. Note that CC TP - AS. Use CC values to interconvert data. An additional 9.1 water was expressed from this substrate between 10 and 60 kPa (to total 100) Total volume of the 5-cm column 722 mL. Note that CC TP - AS. Use CC values to interconvert data. An additional 9.1 water was expressed from this substrate between 10 and 60 kPa (to total 100) Total volume of the 5-cm column 722 mL. Note that CC TP - AS. Use CC values to interconvert data. An additional 9.1 water was expressed from this substrate between 10 and 60 kPa (to total 100) Total volume of the 5-cm column 722 mL. Note that CC TP - AS. Use CC values to interconvert data. An additional 9.1 water was expressed from this substrate between 10 and 60 kPa (to total 100) Total volume of the 5-cm column 722 mL. Note that CC TP - AS. Use CC values to interconvert data. An additional 9.1 water was expressed from this substrate between 10 and 60 kPa (to total 100) Total volume of the 5-cm column 722 mL. Note that CC TP - AS. Use CC values to interconvert data. An additional 9.1 water was expressed from this substrate between 10 and 60 kPa (to total 100) Total volume of the 5-cm column 722 mL. Note that CC TP - AS. Use CC values to interconvert data. An additional 9.1 water was expressed from this substrate between 10 and 60 kPa (to total 100)
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Determination of Leaching Fraction
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Substrate Technology, Water and Mineral Nutrition
in Protected Agriculture Workshop
Day 3 Topic 9
Knowledge Center - Access to Online Resources
Andrew G. Ristvey Extension Specialist
Commercial Horticulture
University of Maryland Extension Wye Research
and Education Center College of Agriculture and
Natural Resources University of Maryland
89
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Substrate Technology, Water and Mineral Nutrition
in Protected Agriculture Workshop
Day 4 Topic 10
Advanced Management Plant Water Requirements and
Real-time Monitoring
Andrew G. Ristvey Extension Specialist
Commercial Horticulture
University of Maryland Extension Wye Research
and Education Center College of Agriculture and
Natural Resources University of Maryland
94
Significance for the Industry
(Ristvey, 2004)
95
Current Focus

Deployed Three Networks
Working through implementation issues with
growers
Placement, variability, interpretation issues
Integration with irrigation control systems
Performance
Calibration of sensors soilless substrate
characterization
Sensor placement in the root zone real-time
monitoring of readily-available H20 and EC
Monitoring and control of irrigation events w/
both data streams

96
1. Raemelton Network

Fully integrates all Ech20 sensors
plus a number of other sensors
Node runs off 5 AA batteries
life dependent on sensors
and frequency of sensing
At least 6-month battery life
Plug n play operation
Line of sight transmission
No control capability
Only five sensors per node

97
Production System Variability Soil Systems

More Extensive Root Systems
Custom Ech20-5cm sensor
calibration for both blocks
Sensor placement issues very
important
Tree Water Status
Control / promote growth
Reduction in pruning frequency
Improve nutrient uptake efficiency

98
Soil Sensor Data
18 sensor
12 sensor
6 sensor
99
Soil Sensor Data Cornus florida
Irrigation event
0.4 Rain event
1.5 Rain event
100
Soil Sensor Data Acer rubrum
No response from 6 sensor after 1.5 rain event
101
Sensor Performance