1

Is Hydroponics Really that Easy?Petrus Langenhoven, Ph.D.

Horticulture and Hydroponics Crops SpecialistJanuary 5, 2017

Outline

2

• What is Hydroponics?• Container Media/Substrates• Nutrient Solution Management

… Electrical Conductivity (EC)… pH… Alkalinity and control

• Irrigation Water Chemical Quality… Greenhouse Irrigation Water Quality

Guidelines

• Nutritional Disorders• Irrigation Water Biological Quality

… Monitoring Biological Quality of Irrigation Water

• Hype Around Organic Hydroponics

3

What is Hydroponics?

What is Hydroponics?

4

• The word hydroponics technically means working water, stemming from the Latin words "hydro" meaning water, and "ponos" meaning labor.

• Hydroponics is a subset of hydroculture and is a method of growing plants using mineral nutrient solutions, in water, without soil.

• Two types of hydroponics, solution culture and medium culture.• Solution culture types (only solution for roots)

… Continuous flow solution culture, Nutrient Film Technique (Dr Alan Cooper, 1960’s) … Aeroponics

• Medium culture types (solid medium for roots, sub- or top irrigated, and in a container)… Ebb and Flow (or flood and drain) sub-irrigation… Run to waste (drain to waste)… Deep water culture, plant roots suspended in nutrient solution… Passive sub-irrigation, inert porous medium transports water and nutrients by capillary action. Pot sits in shallow

solution or on a capillary mat saturated with nutrient solution.

5

Photos: Petrus Langenhoven

Main Characteristics of Various Growing Systems

6

Source:Pardossi, A. et al., 2011. Fertigation and substrate management in closed systems

Open versus Closed Soilless Systems

7

Source:Pardossi, A. et al., 2011. Fertigation and substrate management in closed systems

8

Source: http://delphy.nl/en/news/growing-under-100-led-lighting/

2014/15 season

100.6 kg∙m-2 = 20.6 lb∙ft-2

or1006 ton∙ha-1 = 449 US tons∙acre-1

or1006 ton∙ha-1 = 897,352 lbs∙acre-1

9

Container Media / Substrates

Characteristics of an Ideal Container Substrate

10

Generally growers select a substrate based on its availability and cost, as well as local experienceDrain fraction of at least 20 – 25% is used to prevent root zone salinization• Adequate mechanical properties to guarantee plant stability• Low bulk density; bulk density lower than 900 kg∙m3 and maybe as low as 80-120 kg∙m3 (light weight)• High total porosity (70-90%), sum of macropores and micropores. Good water-holding capacity (50-65%). Available

water (>30%). Air capacity (10-20%). Good aeration and drainage• High permeability to air and water. Even distribution of air and water to sustain root activity• pH of between 5.4 and 6.6 (dolomitic or calcitic limestone can be added to adjust pH)• Low soluble salts content• Chemically inert• High cation exchange capacity (CEC), capacity of substrate to hold positively charged ions; ideal level of about 6-15 meq

per 100 cc• Ability to maintain the original characteristics during cultivation• Absence of pathogens and pests• Availability in standardized and uniform batches

11

Popular Container Media/SubstratesInorganic Media

Organic MediaNatural Synthetic

Sand Foam mats (Polyurethane) Sawdust

Gravel Polystyrene Foam Composted Pine Bark

Rockwool “Oasis” (Plastic Foam) Wood chips

Glasswool Hydrogel Sphagnum Peat moss

Perlite Biostrate Felt® (Biobased Product) Coir (Coconut Peat/Fiber)

Vermiculite Rice Hulls

Pumice

Expanded Clay

Zeolite

Volcanic Tuff

pH of Different Media | Cation Exchange Capacity

12

CEC - Capacity to hold and exchange mineral nutrients

Rockwool Perlite

13

60% diabase (form of basalt rock, dolerite), 20% limestone, and 20% coke

Melted at 2912°F, spun at high speed into thin fibers

Heated with phenolic resin and wetting agent to bind them together and lower the natural hydrophobicity of the material. Pressed into slabs

Characteristics: Low bulk density and high porosity High water-holding capacity (80%) and good

aeration Chemically inert with pH 6.0 to 6.5 No CEC or buffering capacity Dissolve at low pH, below 5.0 Reusable. Can last for up to 2 seasons

Naturally occurring, nonrenewable, inorganic, siliceous volcanic rock

Grinded and popped at ±1800°F. Expands to between 4 and 20 times larger

Characteristics: Lightweight, sterile, white, porous aggregate Finished product is a “closed cell” that does

not absorb water. Water will adhere to surface

Usually included in mixture to improve drainage or increase aeration

Neutral pH of between 6.5 and 7.5 Low CEC Chemically inert

Vermiculite Coconut Coir

14

It’s a mica-like, silicate mineral Contains mineral water between ore plates When heated at 1832°F, ore plates move

apart into an open, accordion-like structure Characteristics:

Very light, high water retention and good aeration Low bulk density pH value is 7 to 7.5, and low EC Low pH can release Al into the solution Has a permanent negative electrical charge, and

therefore CEC is high High nutrient content (K, Ca and Mg) Used as component of mixes and in propagation

Coconut fiber / dust is an agricultural waste product derived from the husk of coconut fruit

Alternative to peat moss and bark Composted for 4 months Characteristics:

Can have high amounts of salts Water and air content varies according to texture

components More fiber – High air and low water content More peat – a lot of water and little air

Coir is hydrophilic, disburse evenly over the surface of fibers

Higher pH than peat moss, pH is 5 to 6 Not inert and can store lots of nutrients, high CEC Require more Ca, S, Cu and Fe than peat moss. Greater N-

immobilization than peat moss May contain excessive levels of K, Na and Cl. Soak and rinse

well before use Use for up to 2 - 3 years

Composted or Aged Pine Bark Sphagnum Peat Moss

15

Partially decomposed sphagnum moss, predominantly from Canada

Available in different colors, indicate degree of decomposition

Light-colored peat, larger particles and limited decomposition. Provides excellent aeration and decompose faster than black peat

Black peat is highly decomposed, physical properties vary greatly

Characteristics: High water-holding capacity High air capacity Naturally acidic with pH value between 3.0 to 4.0 Low nutrient content, but high CEC Naturally hydrophobic when dry Shrinkage results after water evaporates from pot

Used in combination with peat for structure

Predominant substrate in nursery industry

Screened and aged (4-6weeks) Young bark decomposes more rapidly Bark should have little to no white

wood Low bulk density High CEC

Summary of Different Chemical and Physical Properties of Some Common Materials Used to Create Growing Media

16

Source: Wilkinson, K.M. et al., 2014. Tropical Nursery Manual

Examples of Common Substrate “recipes” Growers can Formulate to Produce Greenhouse and Nursery Crops

17

Source: Owen, W.G. and R.G. Lopez, 2015. Purdue Extension Pub. HO-255-W. Evaluating container substrates and their components

18

Nutrient Solution Management

EC

19

Units may be confusing1 mmho∙cm-1

1 dS∙m-1

1 mS·cm-1

10 mS∙dm-1

100 mS∙m-1

1000 µS∙cm-1

CationsH+

Na+

NH4+

K+

Ca2+

Mg2+

AnionsOH-

HCO3-

Cl-NO3

-

H2PO4-

SO42-

EC reading is impacted by temperature

Temp (°F) Temp (°C) EC (mS∙cm-1)

59 15 1.62

68 20 1.80

77 25 2.00

86 30 2.20

Plus micro-nutrients

Electrical Conductivity (EC), depends on how many charged particles are present in the solution. Measure of how well a solution or substrate conducts electricity

What are the Effects of Salt Stress (high EC) on Plants?

20

• Osmotic… Loss of osmotic gradient for water absorption… Worst case scenario: Results in wilting even though the substrate is moist… Prolonged stress may result in reduced growth (shorter internodes and smaller leaves); even without wilting

• Toxic concentrations of ions… Excess absorption of sodium and chloride… Excess absorption of micronutrients such as boron, manganese, iron

• Carbonate and bicarbonate… High pH will impact solubility of nutrients… Over time pH of container substrate will increase… Precipitation of calcium and magnesium

• Nutrient antagonisms… Absorption of one nutrient might be limited by excess concentrations of another

Excessive in Media Low Tissue Level

NH4, Na, K, Ca, Mg Na, K, Ca, or Mg

PO4 Zn or Fe

Ca B

Cl NO3

Source: Paul Nelson

pH scale is logarithmic. Value will not decrease linearly when acid is added or increase linearly when basic is added

21

The logarithmic scale of pH means that as pH increases, the H+ concentration will decrease by a power of 10. Thus at a pH of 0, H+ has a concentration of 1 M. At a pH of 7, this decreases to 0.0000001 M. At a pH of 14, there is only 0.00000000000001 M H+

Sour

ce: F

unda

men

tals

of E

nviro

nmen

tal M

easu

rem

ents

• Half of all nutritional disorders can be attributed to pH-related problems

• pH affects nutrient solubility

• Only dissolved nutrients are taken up by roots

Optimal nutrient availability in hydroponic nutrient solution at pH range of 5.5 to 6.5 | Substrate, generally between 5.4 to 6.4

22

Sour

ce: w

ww

.hyd

rofa

rm.c

om

Influence of pH on the availability of essential nutrients in a soilless substrate (container media) containing sphagnum peat moss, composted bark, vermiculite and sand

Problems associated with out of range substrate pH

Source: Bailey, D.L., P.V. Nelson, and W.C. Fonteno. Substrate pH and Water Quality

Factors Affecting Root Media (substrate) pH

23

• Acidic Media… pH less than 7… Sphagnum peat moss, pine bark, coir, composts

• Neutral Media… pH around 7… Perlite, sand, polystyrene

• Alkaline Media… pH greater than 7… Bark from hardwood trees, vermiculite, rockwool, rice hulls

• Media pH can be altered prior to planting with Limestone (CaCO3) or Dolomite (50% CaCO3 and 40% MgCO3)

• Alkalinity of the water (carbonates/bicarbonates). High alkalinity will increase container media pH over time

• Ammonium or urea based fertilizers will acidify the root media• Fertilizers that are nitrate based tend to increase root media pH over time

Alkalinity

24

• The ability of water to neutralize acids; it buffers water against changes in pH• Reported in terms of parts per million (ppm) CaCO3 or milli-equivalent (meq∙L-1)• Water alkalinity can vary between 50-500 ppm (1-10 meq∙L-1)

meq∙L-1 ppm CaCO3

ppm HCO3

-ppm CO3

2-ppm Ca2+

1 50 61 30 202 100 122 60 403 150 183 90 604 200 244 120 806 300 366 150 120

ElementWeight

MolecularCa 40C 12O 16H 1

Rangemeq·L-1 Classification

0 to 1.5 Low1.5 to 4 Marginal

> 4 High

Alkalinity Recommendations for Container Media

25

Source: University of TennesseeWill, E. and J.E. Faust. Irrigation water quality for greenhouse production

Correcting High Alkalinity

26

• Change or blend the water source (well water, rain, pond, municipal)• Use an acidic fertilizer

… This approach does not work well for container crops in dark, cool weather conditions… Ammonium may sometimes not lower the pH due to high lime in media or due to high alkalinity… Watch out for ammonium toxicity under cool (below 60°F not converted to nitrate) and wet conditions

(winter and early spring). Plants can absorb too much ammonium, and pH will decrease• Acid injection into irrigation water

… Safety – always add acid to water. Nitric acid is very caustic and has harmful fumes… Do not mix acid stock solutions with fertilizer stock solutions… Use a separate injector

• Assess cost of acid source• Take into account that the form of acid used can provide specific nutrients

Characteristics of Acids Used to Neutralize Water Alkalinity

27

Source:Bailey, D.A. Alkalinity control for irrigation water used in greenhouses

28

Irrigation Water Quality, chemical

29

Greenhouse Irrigation Water Quality GuidelinesUpper Limit Optimum Range Comments

pH 7.0 5.5 – 6.5

EC 1.25 mS∙cm-1 Near zero 0.75 mS∙cm-1 for plugs and seedlings. High EC can be the result of accumulation of a specific salt which can reduce crop growth

Sodium absorption ratio (SAR) 4 mg∙L-1 0 – 4 mg∙L-1 Relationship of water’s sodium content to its combined calcium and magnesium. If the SAR is less than 2 mg·L-1 and sodium is less than 40 mg·L-1, then sodium should not limit calcium and magnesium availability

Total Alkalinity (as CaCO3), acid-neutralizing or buffering capacity

150 mg∙L-1 0 – 100 mg∙L-1 Measures the combined amount of carbonate, bicarbonate and hydroxyl ions.30 – 60 mg∙L-1 are considered optimum for plantspH 5.2, 40 ppm alkalinity; pH 5.8, 80 ppm alkalinity; pH 6.2, 120 ppm alkalinity

Hardness (amount of dissolvedCa2+ and Mg2+)

150 mg∙L-1 50 – 100 mg∙L-1 Indication of the amount of calcium and magnesium in the water. Calcium and magnesium ratio should be 3 – 5 mg·L-1 calcium to 1 mg·L-1 magnesium. If there is more calcium than this ratio, it can block the ability of the plant to take up magnesium, causing a magnesium deficiency. Conversely, if the ratio is less than 3-5 Ca:1 Mg, the high magnesium proportion can block the uptake of calcium, causing a calcium deficiency. Equipment clogging and foliar staining problems above 150 ppm

Bicarbonate Equivalent (HCO3-) 122 mg∙L-1 30 – 50 mg∙L-1 Increased pH and can lead to Ca and Mg carbonate precipitation

mg·L-1 = ppm

30

Greenhouse Irrigation Water Quality GuidelinesUpper Limit

Optimum Range Comments

Calcium 120 mg∙L-1 40 – 120 mg∙L-1

Magnesium 24 mg∙L-1 6 – 24 mg∙L-1

Iron 5 mg∙L-1 1 – 2 mg∙L-1 >0.3 mg∙L-1, clogging; 1.0 mg∙L-1, foliar spotting and clogging; above 5.0 mg∙L-1, toxic. Could lead to iron precipitates resulting in plugging of irrigation system emitters

Manganese 2 mg∙L-1 0.2 – 0.7 mg∙L-1 >1.5 mg∙L-1 emitter blockage can occur

Boron 0.8 mg∙L-1 0.2 – 0.5 mg∙L-1

Zink 2 mg∙L-1 0.1 – 0.2 mg∙L-1

Copper 0.2 mg∙L-1 0.08 – 0.15 mg∙L-1

Molybdenum 0.07 mg∙L-1 0.02 – 0.05 mg∙L-1

Sulfate 240 mg∙L-1 24 – 240 mg∙L-1

(60 to 90 mg∙L-1)If the concentration is less than about 50 ppm, supplemental sulfate may need to be applied for good plant growth. High concentrations can lead to build-up of sulfur-bacteria in irrigation lines that could clog emitters.

Chloride 70 mg∙L-1 0 – 50 mg∙L-1 Concern, above 30 mg∙L-1 for sensitive plants

Sodium 50 mg∙L-1 0 – 30 mg∙L-1 If the SAR is less than 2 mg∙L-1 and sodium is less than 40 mg∙L-1, then sodium should not limit calcium and magnesium availability

mg·L-1 = ppm

Alkalinity Affects how much Acid is Required to Change the pH

31

Titrations of two different waters with sulfuric acid. Notice that although the beginning pH of Grower A water is a full unit higher than Grower B water, it takes more than 4 times the acid to drop Grower B water to pH 5.8, due to the greater alkalinity in Grower B water.

Source: Bailey, D.A. Alkalinity control for irrigation water used in greenhouses

32

33

Nutritional Disorders

Key to Visual Diagnosis of Nutrient Disorders

34

Source: N. Mattson. Cornell University. Adapted from: Bierman P.M. and C.J. Rosen. University of Minnesota. http://www.extension.umn.edu/garden/fruit-vegetable/diagnosing-nutrient-disorders/

35

Irrigation Water Quality, biological

Biological Water Quality

36

• Waterborne pathogens and algae can be an issue under moist propagation conditions, and especially with recirculating irrigation systems

• Goal is not to sterilize water but to minimize the pathogen risk from water as part of an overall sanitation program

Monitoring Biological Quality of Irrigation Water

37

• What might you test for? In addition to waterborne pathogens, microbial water issues result in algae growth on growing media and floors, and clogged equipment from bacteriaand biofilm. Human pathogens such as E. coli

• Biological water quality changes very quickly. Repeated testing is advised• Sample at points along the irrigation system can also identify where conditions favor the

growth of microorganisms• Testing for biological quality can help to avoid crop losses and health issues from

contaminated produce. Monitoring is highly recommended• Sanitizing agent technology such as activated peroxygens, chlorine, chlorine dioxide, copper,

heat, ozone, or UV can be used

Water Treatment

38

• Filtration and water pre-treatment underlies all other treatment technologies:… Ultraviolet – clear water for wavelengths to penetrate pathogen cell walls… Oxidizing materials such as chlorine react to any organic material and are therefore less effective in

the presence of growing media and plant debris• Considerations

… Cost… Mode of action: copper and chlorine have a residual downstream effect, whereas other materials

are a single-point treatment (UV); some materials are designed for a continual low-level treatment (e.g. ozone and copper) whereas others are effective as a shock treatment to reduce biofilm (e.g. chlorine dioxide), or are suitable for surface sanitation (e.g. quaternary ammonia products)

… Systems may be designed to work synergistically… Flexibility is needed (seasonal differences in pathogen and algae levels)

• Reading: www.WaterEducationAlliance.org

Advantages and Disadvantages of Most Popular Nutrient Solution Disinfection Methods

39

Source:Pardossi, A. et al., 2011. Fertigation and substrate management in closed systems

40

The Hype Around ‘Organic’ Hydroponics?

USDA Agriculture Marketing Service (AMS)

41

• In 2010 the National Organic Standards Board (NOSB) passed a recommendation onto the National Organic Program called Production Standards for Terrestrial Plants in Containers and Enclosures

• Six years later, the National Organic Program (NOP) felt that there were a few points relating to hydroponic production that were left ambiguous

• In September 2015 , AMS convened the Hydroponic and Aquaponic Task Force to further explore • A sixteen member task force was appointed with the objective to develop a report for the NOSB that:

… describes the current state of technologies and practices used in hydroponics and aquaponics; and… to examines how those practices align or do not align with the Organic Foods Production Act (OFPA) and the USDA

organic regulations• Further, the task force formed three subcommittees:

… one was to describe "organic hydroponic" production and discuss the ways in which it aligns with the Organic Foods Production Act (OFPA) and the USDA organic regulations

… one was to discuss alternative labeling, and… one ("the 2010 Recommendation Subcommittee”) accepted the task of providing clarification and further support for

the position taken in the 2010 NOSB recommendation and consider the alignment of soilless production systems with organic law and regulation

Source: https://www.ams.usda.gov/rules-regulations/organic/nosb/task-forces

USDA Agriculture Marketing Service (AMS)

42

• The 2010 Recommendation Subcommittee found that the crux of their conclusion is to clarify the distinction between organic fertility management and conventional fertility management. It is the management of the soil that is at the heart of organic production. In contrast, in a non organic system it is the management of the fertilizers.

• Report submitted on July 21, 2016 in which recommendations were made to AMS which will use it to take the steps to establish clear standards for these production systems

• Public was invited to provide comments• NOSB met in the Fall of 2016• Board decided to postpone the “controversial” vote. NOSB had a hard time discussing if growers of

hydroponic and container grown crops could continue to label their produce as certified organics.• “Well, growers can, at least for a while. To be more precise; until the next meeting of the advisory

board in April 2017”• “US is an outlier in international commerce as most countries prohibit the organic certification of

soilless hydroponic produce, including the 28 countries of the European Union, Mexico, Japan and Canada.“ www.hortidaily.com

Source: https://www.ams.usda.gov/rules-regulations/organic/nosb/task-forces

Bioponics

43

Organic hydroponics, or bioponics, as this Subcommittee has termed it, is fundamentally and entirely different from conventional (non-organic) hydroponics. Bioponics is a growing method that completely relies on a soil food web micro-biological ecosystem to provide nutrients to a crop. All inputs come from animal, plants and minerals and require biology to convert these raw inputs into plant-usable form.

Source: https://www.ams.usda.gov/rules-regulations/organic/nosb/task-forces

Information Resources

44

University resources – Extension publicationsProfessional magazines

– Greenhouse Grower, www.greenhousegrower.com– Practical Hydroponics and Greenhouses,

www.hydroponics.com.au– Greenhouse Canada, www.greenhousecanada.com

Books– Greenhouse Technology and management, Nicolas Castilla– Greenhouse Operation and Management, Paul V. Nelson– Soilless Culture, Michael Raviv & J. Heinrich Leith– Growing Media for Ornamental Plants and Turf, Kevin

Handreck & Niel Black– Plant Nutrition of Greenhouse Crops, Cees Sonneveld &

Wim Voogt– Hydroponic Food Production, Howard M. Resh

Trade shows and conferences– Indiana Horticulture Congress, January 10-12, 2017 –

Indianapolis IN– Indiana Small Farm Conference, March 2-4, 2017 –

Danville IN– Indoor Ag Con, May 3-4, 2017 – Las Vegas NV– Cultivate’17, July 15-18, 2017 – Columbus OH

Manufacturers and distributors (list is not complete but it’s a good start):

– http://www.tunnelberries.org/single-bay-high-tunnel-manufacturers.html

– http://www.tunnelberries.org/multi-bay-high-tunnel-manufacturers.html

THANK YOU Questions?Contact details:

Dr. Petrus LangenhovenHorticulture and Hydroponics Crop Specialist

Department of Horticulture and Landscape ArchitecturePurdue University

Tel. no. 765-496-7955Email: plangenh@purdue.edu

45