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LHAP 105 Soil and Water Presentation Soil and Water

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Slide 1 LHAP 105Media Introduction Developed by LHAP/Horticulture Olds College - ‹#› Slide 2 Media defined: A component or combination of components designed to give the optimum ratio of AIR, WATER, and MINERALS to a given crop and provide sufficient SUPPORT. (4 Basic Functions) Slide 3 Media Components Sphagnum peat Coir fibre Mineral soils Vermiculite, Perlite Rice Hulls, Sand Pine bark Rockwool What Are They?! Slide 4 Properties of a Container Media A. Physical properties Chemical properties C. Biological properties D. Other desirable characteristics Slide 5 Physical properties – Media must provide: 1. Support Keeps plants upright Anchors roots Slide 6 Bulk Density (Db) Defined = the mass (weight) of dry solids in relation to the bulk (volume) of the media. Db= oven dried weight of media (g) volume of soil (in cc or ml) Slide 7 Bulk Density applied For ease of handling, a light Db is desirable (optimum pore spaces and low pot weight)... but it MUST still support the plant. Slide 8 A. Physical properties 2. Total Porosity Defined: Percentage of media composed of pore spaces *Greenhouse media optimum: 75-85% pore spaces* Slide 9 A. Physical properties 3. Aeration Porosity: MACROPORES Water drains quickly through media with large pores 15-20% Pa= Large Containers (nursery) 20-25% Pa = For Rapid Growth (GH) Slide 10 Physical properties 4. Capillary Porosity MICROPORES Slide 11 Symptoms of poor aeration and prolonged water logging of media Wilting Roots with brown tips Lack of root hairs Sour smell Rotten egg odor Stunted growth Chlorosis in older leaves Necrotic margins Roots forming on stems at media surface Slide 12 Physical properties 5. Stable organic matter (note the difference between STABILITY and SUPPORT) Provides aeration, drainage and water holding capacity Slide 13 Chemical Properties Slide 14 B. Chemical properties Media components can affect mineral content and availability: Slide 15 Chemical properties Cation Exchange Capacity (C.E.C) The sum of the exchangeable cations that media can retain per unit weight Slide 16 B. Chemical properties Hatched areas indicate ranges of Cation Exchange Capacity (meq/L) for media components Slide 17 B. Chemical properties 2. 2. Acceptable pH Determination of Acidity or Alkalinity! GH mixes ideal pH = 5.5-6.5 Slide 18 Availability of Nutrients in relation to media pH https://extension.uga.edu Slide 19 Chemical properties 3. Low soluble salts/initial low fertility Dissolved mineral salts found in media Can be a source of mineral supply - Can also be toxic Slide 20 B. Chemical properties 4. Buffering Capacity described as the media’s ability to resist change in pH *Components with high CEC also have high buffering capacity* Slide 21 BIOLOGICAL PROPERTIES Photo source: Filter Forge Slide 22 C. Biological Properties Two considerations: Presence or absence of Harmful Pathogens 2. Presence or absence of Beneficial Microorganisms Slide 23 Biological Properties 1. Pest free Components are considered sterile from the bag ** Mineral Soil MUST be PASTEURISED prior to use ** Slide 24 Biological Properties 2. Beneficial microorganisms Compost brings biological life to a mix Mycorrhizae… (Myke) Slide 25 D. Other desirable characteristics of media 1. Biologically, physically, chemically stable 2. Standardized and uniform from batch to batch 3. Media components should be: Economical Readily available Easily mixed Light in weight

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Slide 1

LHAP 105Media Introduction

Developed by LHAP/Horticulture Olds College -

‹#›

image12.jpg

Speaker Notes

  • Gather for class:
  • Samples of types of Media
  • Pot with media, water, other container to demo ‘just drained’

Slide 2

Media defined:

A component or combination of components designed to give the optimum ratio of AIR, WATER, and MINERALS to a given crop and provide sufficient SUPPORT.

(4 Basic Functions)

Speaker Notes

  • We’re used to thinking of DIRT or MINERAL SOILS. Media is NOT.
  • These are the four basic functions of Soil
  • Discuss - what are some differences between the DIRT (soil) you find outside and what you find from a greenhouse?

Slide 3

Media Components

Sphagnum peat

Coir fibre

Mineral soils

Vermiculite, Perlite

Rice Hulls, Sand

Pine bark

Rockwool

What Are They?!

image2.jpg image3.jpg image13.jpg

Speaker Notes

  • More about these later - this is what a Component is…
  • Mineral soils made of Sand, Silt, Clay, and O.M. Ours can be a little more complicated/engineered
  • Individual elements determine
  • 1/internal pore spaces in Just Drained Media (AIR/WATER)
  • 2/Particle packing (Compaction, which leads to AIR/WATER)
  • 3/Stability - decomposition/Crushing
  • 4/Ease of Water Extraction by roots
  • 5/ BULK DENSITY

Slide 4

Properties of a Container Media

A. Physical properties

Chemical properties

C. Biological properties

D. Other desirable characteristics

Slide 5

Physical properties – Media must provide:

1. Support

Keeps plants upright

Anchors roots

Slide 6

Bulk Density (Db)

Defined = the mass (weight) of dry solids in relation to the bulk (volume) of the media.

Db= oven dried weight of media (g)

volume of soil (in cc or ml)

Speaker Notes

  • Think about how heavy a container of sand is: lots of weight
  • Think about how light the same container of perlite is: less weight, same volume = lower Bulk Density. Typically large (not necessarily many) pore spaces equate to low Db.
  • Db comes from the scientific abbreviations - like Ft vs Fk (force - total) (force - kenetic) this is Density - bulk

Slide 7

Bulk Density applied

For ease of handling, a light Db is desirable (optimum pore spaces and low pot weight)...

but it MUST still support the plant.

Speaker Notes

  • LOW pot weight is ideal - pick the lightest weight container and media mix that will allow adequate support.
  • low Db material (light pots, pores): (Vermiculite) - crush, tip, dry out
  • High Db (Support): (Sand / Soil) - Big Heavy pots - Inert, Compaction, Variability
  • So we mix them.
  • The first question is always WHAT IS MY CROP???

Slide 8

A. Physical properties

2. Total Porosity

Defined: Percentage of media composed of pore spaces

*Greenhouse media optimum: 75-85% pore spaces*

Speaker Notes

  • Inversely related to bulk Density: MORE AIR = LESS DENSITY
  • It provides media with AIR and WATER… Media is not just solids. You have to think of negative space as well (that’s where the roots grow). More pore space = better root development. (JUST Enough Db to support the plant). The process of respiration requires oxygen. Beneficial microorganisms require oxygen.
  • Primary difference between Mineral Soil and soilless media
  • Optimal mineral soils are 50% solids, 50% Pore spaces
  • Mishandling is a real problem: crushing vermiculite or compacting root zones with improper planting techniques
  • Discuss: why 75-85% - our emphasis is NOT on SELF-SUSTAINABILITY. our Emphasis is on - Optimum crop development. Ergonomics, Bench engineering, sanitation, lower costs for higher profit...

Slide 9

A. Physical properties

3. Aeration Porosity: MACROPORES

Water drains quickly through media with large pores

15-20% Pa= Large Containers (nursery)

20-25% Pa = For Rapid Growth (GH)

Speaker Notes

  • Critical to plant health : provides gas exchange to and from roots
  • ‘just drained’ media large pores are filled with air after Gravitational Water exits
  • Gravitational water: draws air down into the container as it moves through it - one reason why you need to water till they ‘pee’ and not let them sit in water which will leach back up into the pot when the top dries out.
  • Good aeration depends on the amount of large pore spaces

Slide 10

Physical properties

4. Capillary Porosity

MICROPORES

image1.jpg image9.jpg

Speaker Notes

  • Just Drained Media, water is still held in small pore spaces (Field Capacity) - think damp soil vs water logged
  • Available water stays as coating on particle surfaces called capillary pores - in these, water can move through the forces of adhesion and cohesion; allowing water to move upward against the force of gravity (why bottom watering works)
  • It is used via Evapotranspiration
  • what is left is Unavailable water - bound too tightly to particle surface (Perm wilting point)
  • Beware of pot size:
  • Taller containers have better drainage… gravity overcomes surface tension of water until a certain point and then a PERCHED WATER TABLE is formed. This is in the same place regardless of pot size because the force of gravity doesn’t change. In a small pot, the saturation zone is almost all of it; whereas in a tall pot, only ⅙ of it is saturated. Saturation zone is dependant on media blend / pore sizes (not pot size).
  • (@air entry point, menisci form. Gravity eventually does not supply enough weight to move water through macropores. surface tension of meniscus prevents droplets. Practical Drainage for Golf, Sportsturf and Horticulture By Keith McIntyre, Bent Jakobsen pages 73-76)
  • capillary rise using adhesion and cohesion counteracts gravity
  • http://toolboxes.flexiblelearning.net.au/archive/tour/turf/html/pages/office/grass_roots/perched.html

Slide 11

Symptoms of poor aeration and prolonged water logging of media

Wilting

Roots with brown tips

Lack of root hairs

Sour smell

Rotten egg odor

Stunted growth

Chlorosis in older leaves

Necrotic margins

Roots forming on stems at media surface

image6.png image4.jpg

Speaker Notes

  • roots picture: E. Kawahara 2014

Slide 12

Physical properties

5. Stable organic matter

(note the difference between STABILITY and SUPPORT)

Provides aeration, drainage and water holding capacity

Speaker Notes

  • Growing On Media: Largely O.M such as Peat or Coir (vs germination media)
  • Choose one that decomposes slowly, and resists compaction (both destroy macropores)

Slide 13

Chemical Properties

image8.png

Speaker Notes

  • https://infoag.org/media/abstracts/5543_Conference_presentation_(pdf)_1532466987_InfoAg2018_Veum.pdf

Slide 14

B. Chemical properties

Media components can affect mineral content and availability:

Speaker Notes

  • Field soils have minerals naturally present and simply need augmenting. MEDIA generally has little to none so we must FERTILIZE to provide it.
  • Understand how components affect mineral availability to inform decisions about what to fertilize with (analysis and formulation) and when.
  • Many soils, sawdusts, and barks supply trace elements, therefore soil testing is important to ensure good growing conditions - don’t just buy whatever’s cheap and easy.
  • Bark and sawdust, if not broken down will rob nitrogen to continue the decomposition process.

Slide 15

Chemical properties

Cation Exchange Capacity (C.E.C)

The sum of the exchangeable cations that media can retain per unit weight

Speaker Notes

  • (To be covered in soils) - Elemental minerals have an electrical charge of + or ++.
  • Individual components can be more or less prone to holding onto the elements in Fertilizers, water, etc. depending on amount of surface area and/or base charge.
  • know what is naturally available (soil test) & What is available in your water. The higher the CEC, the better.
  • Water Holding Capacity is directly related.
  • IF you feed constant fertilizer, you can sacrifice CEC in your soils (because you’ll need less)
  • If you use Bark Mulch uses N to decompose, boost your N inputs or use one that’s not decomposing (or vermiculite / perlite)
  • Water soluble fertilizers require adequate water holding capacity

Slide 16

B. Chemical properties

Hatched areas indicate ranges of Cation Exchange Capacity (meq/L) for media components

image5.jpg

Speaker Notes

  • measured in milliequivalents per litre
  • Zeolites are microporous minerals that give off steam when heated. rarely pure. often contaminated by other surrounding materials
  • Lignites are brown, combustible, sedimentary rock. High carbon content, High moisture. Good Ash content.
  • Perlite and Sand will hold NONE
  • Peat holds a lot, as do vermiculite and clay

Slide 17

B. Chemical properties

2. 2. Acceptable pH

Determination of Acidity or Alkalinity!

GH mixes ideal pH = 5.5-6.5

Speaker Notes

  • pH: the Concentration of hydrogen ions in a media solution - dictates how acidic or alkaline the media is. The higher the concentration of ions, the LOWER the pH number (0-14)
  • In order to be acidic then, a substance must contain hydrogen, in a form that can be released into water. Substances such as CH4 (methane) are not acidic as all four hydrogens are bound very tightly to the carbon and are not going anywhere. CH4 has a neutral pH, around 7. On the other hand, substances such as hydrochloric acid, HCl, are held together by polar ionic bonds and when placed into water the hydrogen will break away to form hydrogen ions, making the liquid acidic. HCl therefore has a very low pH and is a very strong acid.
  • pH Controls nutrient availability - for example, you might have LOTS of phosphorus, but it is tied up in the soil by the pH (less than 5.5) Aluminum and Manganese reach toxic levels that low.
  • pH of 7 is said to be neutral, but it isn’t the optimum for plant development.
  • GH Mix ideal is 5.5 - 6.5
  • Specific crops have different preferences: Azaleas prefer acidic, Easter lilies want 6.5-6.8 b/c it reduces flouride availabilty (reduces toxicity and leaf scorch)
  • Seed Geranium and marigold are susceptible to iron and manganese toxicity (6.2-6.5)

Slide 18

Availability of Nutrients in relation to media pH

https://extension.uga.edu

image11.png

Speaker Notes

  • Media – maximum nutrients available at 5.5 – 6.5
  • Mineral soil – maximum nutrients available at 6.0 – 7.0
  • https://extension.uga.edu/publications/detail.html?number=B1256&title=Essential%20pH%20Management%20in%20Greenhouse%20Crops:%20pH%20and%20Plant%20Nutrition

Slide 19

Chemical properties

3. Low soluble salts/initial low fertility

Dissolved mineral salts found in media

Can be a source of mineral supply - Can also be toxic

Speaker Notes

  • Soluble salts are from fertilizers, O.M. (manures) and water impurities (soft water)
  • High levels lead to root burn, mineral dilution (as Na overwhelms positives), and an inability to take up water.
  • Start with low initial fertility and add more / customize for your crops

Slide 20

B. Chemical properties

4. Buffering Capacity

described as the media’s ability to resist change in pH

*Components with high CEC also have high buffering capacity*

Speaker Notes

  • allows less media testing and inputs
  • know what is naturally available (soil test), & how the minerals interact (water test for hard/soft and pH) before you decide on your additives (fertilizer)

Slide 21

BIOLOGICAL PROPERTIES

Photo source: Filter Forge

image10.png

Speaker Notes

  • Photo retrieved from https://www.gardenmyths.com/soil-bacteria-myth-identification-managment/

Slide 22

C. Biological Properties

Two considerations:

Presence or absence of Harmful Pathogens

2. Presence or absence of Beneficial Microorganisms

Slide 23

Biological Properties

1. Pest free

Components are considered sterile from the bag

** Mineral Soil MUST be PASTEURISED prior to use **

Speaker Notes

  • High heat during production kills any pathogens in vermiculite and perlite
  • Acidic peat has no disease growth at low pH
  • the greatest danger is unsanitary conditions and introduction of fungal infections.
  • more on pasteurization later.

Slide 24

Biological Properties

2. Beneficial microorganisms

Compost brings biological life to a mix

Mycorrhizae… (Myke)

image7.jpg

Speaker Notes

  • Mycorrhizae – describes a beneficial symbiotic association between a fungus and roots of a vascular plant.
  • Fungi use the carbon sequestered; and assist with absorption of water and minerals via hyphae therefore a stronger plant provides greater growth and disease resistance. (it requires organic matter to support fungal life, and are naturally occurring in organic soils)
  • Often it’s being incorporated in GH mixes from factory, and can be purchased at Garden Centres for home use (some will even increase warranty if you buy it).
  • http://www.usemyke.com/en-us
  • http://awaytogarden.com/feed-the-soil-my-experiment-with-mycorrhizae/

Slide 25

D. Other desirable characteristics of media

1. Biologically, physically, chemically stable

2. Standardized and uniform from batch to batch

3. Media components should be:

Economical

Readily available

Easily mixed

Light in weight

Speaker Notes

  • Stability applies primarily to SOIL mixes (weed seeds must be destroyed/ as well as pathogens and parasites) and Mixes with biodegrading components like Bark Mulch
  • You want your media to be relatively unchanging so that you don’t have to be testing it every 5 minutes! Producing a consistent product is the key to return customers.

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