Is Hydroponics Really That Easy?

Is Hydroponics Really that Easy?

Petrus Langenhoven, Ph.D. Horticulture and Hydroponics Crops Specialist January 5, 2017 1 Outline

• What is Hydroponics? • Irrigation Water Chemical Quality • Container Media/Substrates … Greenhouse Irrigation Water Quality Guidelines • Nutrient Solution Management … Electrical Conductivity (EC) • Nutritional Disorders … pH • Irrigation Water Biological Quality … Alkalinity and control … Monitoring Biological Quality of Irrigation Water • Hype Around Organic Hydroponics

2 What is Hydroponics?

3 What is Hydroponics?

• 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.

4 Photos: Petrus Langenhoven

5 Main Characteristics of Various Growing Systems

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

6 Open versus Closed Soilless Systems

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

7 2014/15 season

100.6 kg∙m-2 = 20.6 lb∙ft-2 or 1006 ton∙ha-1 = 449 US tons∙acre-1 or 1006 ton∙ha-1 = 897,352 lbs∙acre-1

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

8 Container Media / Substrates

9 Characteristics of an Ideal Container Substrate Generally growers select a substrate based on its availability and cost, as well as local experience Drain 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

10 Popular Container Media/Substrates

Inorganic Media Organic Media Natural 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

11 pH of Different Media | Cation Exchange Capacity CEC - Capacity to hold and exchange mineral nutrients

12 Rockwool Perlite

 60% diabase (form of basalt rock, dolerite),  Naturally occurring, nonrenewable, 20% limestone, and 20% coke inorganic, siliceous volcanic rock  Melted at 2912°F, spun at high speed into thin fibers  Grinded and popped at ±1800°F. Expands to between 4 and 20 times larger  Heated with phenolic resin and wetting agent to bind them together and lower the natural  Characteristics: hydrophobicity of the material. Pressed into  Lightweight, sterile, white, porous aggregate slabs  Finished product is a “closed cell” that does  Characteristics: not absorb water. Water will adhere to  Low bulk density and high porosity surface  High water-holding capacity (80%) and good  Usually included in mixture to improve aeration drainage or increase aeration  Chemically inert with pH 6.0 to 6.5  Neutral pH of between 6.5 and 7.5  No CEC or buffering capacity  Low CEC  Dissolve at low pH, below 5.0  Chemically inert  Reusable. Can last for up to 2 seasons

13 Vermiculite Coconut Coir

 It’s a mica-like, silicate mineral  Coconut fiber / dust is an agricultural waste product derived from the husk of coconut fruit  Contains mineral water between ore plates  Alternative to peat moss and bark  When heated at 1832°F, ore plates move  Composted for 4 months apart into an open, accordion-like structure  Characteristics:  Characteristics:  Can have high amounts of salts  Water and air content varies according to texture  Very light, high water retention and good aeration components  Low bulk density  More fiber – High air and low water content  pH value is 7 to 7.5, and low EC  More peat – a lot of water and little air  Low pH can release Al into the solution  Coir is hydrophilic, disburse evenly over the surface of fibers  Has a permanent negative electrical charge, and therefore CEC is high  Higher pH than peat moss, pH is 5 to 6  Not inert and can store lots of nutrients, high CEC  High nutrient content (K, Ca and Mg)  Require more Ca, S, Cu and Fe than peat moss. Greater N-  Used as component of mixes and in propagation 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 14 Composted or Aged Pine Bark Sphagnum Peat Moss

 Used in combination with peat for  Partially decomposed sphagnum moss, structure predominantly from Canada  Available in different colors, indicate degree of  Predominant substrate in nursery decomposition industry  Light-colored peat, larger particles and limited  Screened and aged (4-6weeks) decomposition. Provides excellent aeration and decompose faster than black peat  Young bark decomposes more rapidly  Black peat is highly decomposed, physical  Bark should have little to no white properties vary greatly wood  Characteristics:  Low bulk density  High water-holding capacity  High air capacity  High CEC  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 15 Summary of Different Chemical and Physical Properties of Some Common Materials Used to Create Growing Media

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

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

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

17 Nutrient Solution Management

18 Electrical Conductivity (EC), depends on how many charged particles are present in the solution. Measure of how well a solution or substrate conducts electricity Cations EC H+ Units may be confusing Na+ 1 mmho·cm-1 NH + 1 dS·m-1 4 K+ 1 mS·cm-1 Ca2+ 10 mS·dm-1 Mg2+ Plus micro- 100 mS·m-1 Anions nutrients 1000 µS·cm-1 OH- EC reading is impacted by temperature HCO - -1 3 Temp (°F) Temp (°C) EC (mS·cm ) Cl- 59 15 1.62 - NO3 68 20 1.80 - H2PO4 2- 77 25 2.00 SO4 86 30 2.20 19 What are the Effects of Salt Stress (high EC) on Plants?

• 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 Excessive in Media  Low Tissue Level • Carbonate and bicarbonate … High pH will impact solubility of nutrients NH4, Na, K, Ca, Mg Na, K, Ca, or Mg … Over time pH of container substrate will increase PO Zn or Fe … Precipitation of calcium and magnesium 4 • Nutrient antagonisms Ca B … Absorption of one nutrient might be limited by excess concentrations of another Cl NO3 Source: Paul Nelson

20 pH scale is logarithmic. Value will not decrease linearly when acid is added or increase linearly when basic is added • Half of all nutritional

Measurements disorders can be attributed to pH- related problems

• pH affects nutrient solubility

• Only dissolved nutrients are taken up by roots Source: Fundamentals of EnvironmentalSource: Fundamentals

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+ 21 Optimal nutrient availability in hydroponic nutrient solution at pH range of 5.5 to 6.5 | Substrate, generally between 5.4 to 6.4

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 www.hydrofarm.com Source: Source:

Source: Bailey, D.L., P.V. Nelson, and W.C. Fonteno. Substrate pH and Water Quality 22 Factors Affecting Root Media (substrate) pH • 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

23 Alkalinity

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

Range -1 ppm ppm ppm ppm Weight -1 Classification meq∙L - 2- 2+ Element meq∙L CaCO3 HCO3 CO3 Ca Molecular 0 to 1.5 Low 1 50 61 30 20 Ca 40 1.5 to 4 Marginal 2 100 122 60 40 C 12 3 150 183 90 60 > 4 High O 16 4 200 244 120 80 H 1 6 300 366 150 120

24 Alkalinity Recommendations for Container Media

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

25 Correcting High Alkalinity

• 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

26 Characteristics of Acids Used to Neutralize Water Alkalinity

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

27 Irrigation Water Quality, chemical

28 Greenhouse Irrigation Water Quality Guidelines Upper 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 -1 -1 Total Alkalinity (as CaCO3), 150 mg∙L 0 – 100 mg∙L Measures the combined amount of carbonate, bicarbonate and hydroxyl ions. acid-neutralizing or buffering 30 – 60 mg∙L-1 are considered optimum for plants capacity pH 5.2, 40 ppm alkalinity; pH 5.8, 80 ppm alkalinity; pH 6.2, 120 ppm alkalinity Hardness (amount of dissolved 150 mg∙L-1 50 – 100 mg∙L-1 Indication of the amount of calcium and magnesium in the water. Calcium and Ca2+ and Mg2+) 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 - -1 -1 Bicarbonate Equivalent (HCO3 ) 122 mg∙L 30 – 50 mg∙L Increased pH and can lead to Ca and Mg carbonate precipitation

mg∙L-1 = ppm

29 Greenhouse Irrigation Water Quality Guidelines Upper Optimum Range Comments Limit 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 If the concentration is less than about 50 ppm, supplemental sulfate may need to be applied for good (60 to 90 mg∙L-1) 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 30 Alkalinity Affects how much Acid is Required to Change the pH

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 31 32 Nutritional Disorders

33 Key to Visual Diagnosis of Nutrient Disorders

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/ 34 Irrigation Water Quality, biological

35 Biological Water Quality

• 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

36 Monitoring Biological Quality of Irrigation Water

• 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 bacteria and 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

37 Water Treatment • 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

38 Advantages and Disadvantages of Most Popular Nutrient Solution Disinfection Methods

Source: Pardossi, A. et al., 2011. Fertigation and substrate management in closed systems 39 The Hype Around ‘Organic’ Hydroponics?

40 USDA Agriculture Marketing Service (AMS) • 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 41 USDA Agriculture Marketing Service (AMS) • 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 42 Bioponics

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 43 Information Resources

University resources – Extension publications Trade shows and conferences Professional magazines – Indiana Horticulture Congress, January 10-12, 2017 – – Greenhouse Grower, www.greenhousegrower.com Indianapolis IN – Practical Hydroponics and Greenhouses, – Indiana Small Farm Conference, March 2-4, 2017 – www.hydroponics.com.au Danville IN – Greenhouse Canada, www.greenhousecanada.com Books – Indoor Ag Con, May 3-4, 2017 – Las Vegas NV – Greenhouse Technology and management, Nicolas Castilla – Cultivate’17, July 15-18, 2017 – Columbus OH – Greenhouse Operation and Management, Paul V. Nelson Manufacturers and distributors (list is not – Soilless Culture, Michael Raviv & J. Heinrich Leith complete but it’s a good start): – Growing Media for Ornamental Plants and Turf, Kevin Handreck & Niel Black – http://www.tunnelberries.org/single-bay-high-tunnel- – Plant Nutrition of Greenhouse Crops, Cees Sonneveld & manufacturers.html Wim Voogt – http://www.tunnelberries.org/multi-bay-high-tunnel- – Hydroponic Food Production, Howard M. Resh manufacturers.html

44 THANK YOU Questions?

Contact details:

Dr. Petrus Langenhoven Horticulture and Hydroponics Crop Specialist Department of Horticulture and Landscape Architecture Purdue University Tel. no. 765-496-7955 Email: [email protected]

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