A lot of people are asking us: "How can I grow vegetables in my house?" 'Is there a way to grow herbs in-house?'. This article is for you.

Part 1: What is Hydroponics?

Growing hydroponically (or growing "soil-less") is a popular farming technique. Using mineral nutrient solutions in an aqueous solvent (e.g., water) enables you to produce healthy, flavorful plants in a controlled way and with much less water than traditional agriculture. With concerns about freshwater availability and sustainability, hydroponics is an attractive alternative for urban and rural farmers.

Most plants can grow hydroponically. Your plants won't drown if you keep your water regularly oxygenated, circulated, filtered, and refreshed. With the right care, you’ll be able to grow healthy plants.

In this article, we'll share what you need to start and run a successful hydroponic. You will learn how to monitor and control EC, pH, source water quality, temperature, filtration, lighting, and many other factors.

In this article, you will learn about: 

• The origins of hydroponics
• Hydroponic system types
• Hydroponic nutrient management
• Hydroponic system layouts and plumbing
• The best crops for hydroponics

1. Soil-less Production

Keynotes:

• You can replace the soil, but you must replicate the functions of the soil 
• Substrate plugs help to anchor plants in hydroponic systems 
• Hydroponic systems deliver water mechanically, aeration of roots is vital
• In hydroponics, plants receive nutrients through formulated solutions.
• In hydroponics, it's essential to provide environmental stability  

Let's take a look at the functions of soil for a plant, so we know what functions a soil-less system must provide for healthy plants. 

Soil helps to:

• Anchor plants 
• Hold water
• Hold Nutrients
• Provide environmental stability; e.g., humidity, temperature, oxygen
• Regulate the flux of nutrients with microbes

A soil-less system would need to:

• Anchoring plants artificially
• Supply water mechanically
• Provide Nutrients from a formulated solution
• Supply microbes through cultural techniques
• Be in a controlled environment  

Anchoring

A standard anchoring method is to place the seed in a soil plug and drop it into a trough system in horizontal hydroponics. The plug will fit in a hole and, in a horizontal set-up, the weight of the plug and plant will keep it in place. 

In vertical hydroponics, it is more important to anchor the plants well. In vertical grow towers, the plugs need to be tightly gripped in, e.g., rockwool or matrix media.

Water

In hydroponic systems, you can deliver water mechanically by pumping it to the plants. You can either run this pump continuously or at regular intervals. Pumping the water around will help circulate the nutrients and avoid the nutrients settling down in your basin or tank. Make sure you are not over-irrigating, and proper oxygenation is also essential. 

Nutrients

In hydroponics, you will provide nutrients to the plants by pumping the water to the roots. The nutrient and water level should be sufficient to help you keep your growth rates up. For nutrients, you can use a formulated solution. 

Follow the instructions on the nutrient bottle when mixing it with water. The great thing about using formulated solutions is that you will know what you used, and you can keep the nutrients constant or play around and see if growth increases.

When you buy hydroponic nutrients, make sure that the solution is made specifically for a hydroponic system. Do not use nutrients for soil-based cultivation. The soil has a different nutrient composition; for example, the earth is an excellent nitrogen source. As a result, soil-based nutrient solutions won't contain a lot of nitrogen. Hydroponic systems do not have soil that contains nitrogen, and they require nitrogen in its nitrate form.

Microbes

Beneficial microbes and plants have a symbiotic relationship. A plant can make food for microbes in the root zone. In return, those microbes can protect the plant from stress and feed the plant by converting and holding nutrients. Rockwool, vermiculite, or other substrates can replicate the habitat for microbes. 

Controlled environment

A controlled environment will help you to get the best out of hydroponic cultivation. You protect the roots and shoots from damage and temperature swings with a stable climate. You can do this pro-actively in a controlled environment, like a greenhouse, climate chamber, or grow tent, by actively heating or cooling the space artificially, which keeps the environment perfect for your plants. 

Conclusion

The purpose of the introduction was to help you understand soil functions and what you would need to consider if you are growing without soil. You learned about plant anchoring, water, nutrients, microbes, and the controlled environment in hydroponics.

Next, we will briefly discuss the history of hydroponics.

2. History of Hydroponics

Keynotes:

• Many ancient civilizations used some kind of hydroponic planting technique 
• The development of solutions that contained nutrients was a breakthrough
• During World War II, people used hydroponics to produce food 
• The rise of plastics enabled NFT for commercial application
• Automation and sensors helped to scale up hydroponics 
• Nowadays, hydroponics can help people to grow anything, anywhere 

Perhaps the word hydroponics sounds advanced, and therefore we assume it is a recent technology. There are clues that it has been in use for a long time.

Hydroponics in ancient civilizations

The hanging gardens of Babylon were built along the Euphrates River in Babylonia. Since the region's climate was dry and rarely saw rain, some people believe that the ancient gardeners used a chain pull system for watering the garden plants. There are other hunches in other civilizations; Egyptian hieroglyphics depict plants that grow without soil, Marco Polo wrote about floating gardens in China. The Aztecs grew on organic matter on floating islands. 

Hydroponics in the 1600s–1930s

From the 1600s to the 1930s, some people experimented with water culture and nutriculture. They started to understand that plants needed water with nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), sulfur (S), and calcium (Ca). Scientists started to make nutrient recipes. Hoagland developed The Hoagland Solution, one of the first formulated solutions for commercial use.

Around this time, the technique became known as "hydroponics", from the Greek words: "hydro" meaning "water" and "ponos" meaning "work".  

Hydroponics used to provide food in World War II

During world war II, there were soldiers based in islands on tiny little islands in the Pacific. They needed fresh fruits and vegetables but had few natural resources on the islands. The US military used hydroponics to supply troops on non-arable islands in the pacific. 

The rise of plastics enabled commercial hydroponic facilities

In the 1970s, the production and use of plastics became mainstream. Suddenly greenhouses could use plastic films and cover and protect crops. Plastics were a lot more cost-effective and offered better protection.  

The rise of electronics helped controlled environment agriculture

Controllers and nutrient injectors arrived in the 1980s and the 1990s. Sensors meant that systems could have automated dosing, automated control, and a controlled environment for plants. 

Greenhouses use hydroponic systems on a massive scale

Greenhouse hydroponics is very popular. Growers specialized in producing vegetables and fruiting vegetables in the greenhouse, which helps to get a more stable supply of fresh food, fewer diseases, and less dirt in a more environmentally friendly way. Innovations in breeding and technology, including supplemental lighting, meant that the yield per m2 has dramatically increased from, e.g., 2kg of tomatoes per m2 on the field to about 80kg per m2 in controlled greenhouses. 

Indoor hydroponics enable you to grow anything, anywhere, all-year-round

With the rise of LED as lighting technology, indoor growth without any natural daylight has become possible. In combination with hydroponics, it is now possible to have multi-layered plant cultivation in a completely controlled environment. Using grow-lights helps you to grow anything and anywhere, regardless of climate, and grow all-year-round. With the rise of affordable solutions, people can even grow in their spare room. 

Conclusion

Hydroponics has come a long way, and it has attracted people throughout time. With controlled environment agriculture it enables you to grow anything, anywhere at any-time with fewer costs and more output. 

In the next section, we discuss what hydroponic crops you might like to grow.

3. Hydroponic Crops

Keynotes:

• Grow crops that are suitable for your technique, goals, capabilities, and interest
• Grow crops that people want 
• Consider starting with leafy greens and herbs before trying any other crops

Choosing what crops you will grow is an important decision. Especially if you're planning to sell your produce to other people. Potential buyers would like to see the crop before committing to purchase, which creates a product-market fit risk.

However, there are other ways to consider what you should grow. 

Grow crops that are suitable for your space or equipment

If you are keen on a particular technical set-up or have a specific space in mind, you can start to think about how you can make the most of it. 

For example, if you're thinking about growing herbs or leafy greens, a horizontal or vertical hydroponic set-up enables you to do that. If you're keen on a grow-tent, you could consider growing tomatoes or other vine crops in a Dutch bucket or Bato bucket. 

Grow lights enable you to grow indoors, but each plant and growth stage requires a different intensity and spectrum. The light intensity is the amount of plant-centric light received on the plant surface (e.g., leaf). You can describe this as µmol/m2/s, and it is the amount of plant-relevant light per square meter. If you're growing microgreens, you'll need intensities up to 80 µmol/m2/s. If you're growing leafy greens, you might need up to 150 µmol/m2/s. For fruiting vegetables, you might need up to 300 µmol/m2/s. The higher the µmol value, the more power, and efficiency you are going to need. With that comes an increased initial investment and a different return on investment. 

Grow crops that match your goals

You'll have your vision of your farm. So if one of your goals is to eat all-year-round from your farm, you would select various crops. Or, if your goal is to grow pesticide-free, it might mean that you pick a pest-resistant crop. 

Grow crops that match your growing environment

Grow something easy to grow in your environment. For example, if you're in a hot, humid climate, you might choose crops that are happy with slightly warmer temperatures. E.g., many people would like to eat Brussels sprouts. And you could grow Brussels sprouts but should you? Perhaps not, since Brussels sprouts require cooler temperatures. Of course, you can blast cool air in with the air conditioner, but it'll increase your operating costs, and you need to offset that with a relatively high selling price. In this case, it might be worthwhile to grow something else that prefers hot temperatures. 

Grow crops that are in demand

People need to like what you grow. Grow something that you'll know will sell. Don't produce something you can't sell. To find out what would be in demand, you might want to do some market research. 

In the market research, you can find out:

• What is in demand?
• What are large volume crops?
• What crops have the highest margin?
• What crops can I sell in large volumes?

In many markets, the profitable crops are herbs like mint and basil and leafy greens like kale, mustard greens, bok choy, and lettuce. These crops are staple crops and are likely to sell well.

Grow crops that fit your capabilities as a grower

Grow something that you feel confident with and expand more crops as you go. 

You're probably learning by doing. And if you're reading this article, you are interested in growing plants. If you're trying to grow and sell, you need to make sure that you understand your capabilities as well. Start with something that you have cultivated before and that you'll know works well for you. 

Don't go out there and try to grow tomatoes if you've never grown tomatoes before. Tomatoes are difficult, and so are cucumbers, eggplants, and bell peppers. These fruiting crops are challenging because they require phases such as germination, vegetative stage, flowering stage, and fruiting stage.

Learn fast, fail cheaply

Herbs and leafy greens are fast and easy, which brings up one last point here: risk management.

As a grower, you will probably invest a lot of time and money in your crops. So you need to minimize the risk that comes with growing the crops and mitigate if needed. Your crop choice has a significant influence on your risk management.

Grow fast, learn fast, fail cheaply. 

Crops with slow growth cycles are an expensive type of risk.

If you're growing vine crops such as tomatoes, it will take about six months before your tomatoes are producing, and they'll produce for twelve to eighteen months after that, then you'll tear them out and replace them. 

This lengthy timeline increases risks because you need to keep your plants growing well before seeing any productivity or harvest. If something goes wrong in that long timeline, it will be an expensive risk because it took so much time. 

Minimizing risk by growing fast

One way to minimize risk is to grow crops such as microgreens, herbs, or leafy greens that grow fast. E.g., with microgreens, you'll have the results in a week. If you ever have a crop failure, it would never more than seven days away from a solution. And within seven days you would be able to replace the product. But if you're growing tomatoes in month five, it will take another five months to get to a possible new solution that solves a crop failure. Consider the risks and decide what risk is acceptable for you. You can start with leafy greens and herbs and have a small experiment with a high-risk crop. In this way, the high-risk crop will not impact your ability to deliver to your consumers or affect the viability of your farm. 

Vegetative crops are an efficient way to grow.

Vegetative crops are not reproducing, and we're eating the vegetation itself rather than the seeds or fruits.

Vegetative crops are effectively more efficient at taking the inputs you give to them—the water, the nutrients, the light, and the CO2—and convert it into something you can sell.

For fruiting vegetables such as bell pepper, you have to go through vegetative growth and flowering before getting to a fruiting stage.

Should I focus on friends, family, and neighborhood instead of a group of restaurants?

You probably should start small and expand the circle as you go. Seling to people you know enables you to get feedback on what your consumers love, and it will help you to get your farm into a stable operation mode

So should I go with herbs and leafy greens?

Yes, start with leafy greens and herbs. There will always be a broad market, and you can grow them free of pesticides and locally, so you'll have a good selling point and possibly can get significant margins, and since they grow fast, you can do more volume with fewer risks.

Recommended Crops

• Lettuces
• Asian greens like the mustards, bok choy, and tatsoi
• Indian mustards
• Kale

On herbs, mint and basil are our core crops in hydroponic systems. Parsley during the winter is a big deal. Chives do very well. We also grow oregano and a few other crops. 

Conclusion

Picking the right crop is one of the most important things you will do at the beginning. Choose something that fits you and the market. And remember, leafy greens and herbs are something you might consider.

4. Hydroponic Methods

Keynotes:

• The main hydroponic techniques are media bed, NFT, DWC, vertical and aeroponic
• Media beds replace the soil with substrates like sand, sawdust, crushed granite, hydroton, or some other aggregate
• Nutrient film technique or NFT is one of the most popular techniques today
• In Deep water culture or DWC, plants grow on top of a floating raft. It is also known as raft production
• Vertical farms stack multiple layers with plant plug holes on the horizontal plane or volumetric vertical planes
• Aeroponic production uses misting nozzles to form a mist of nutrient solution on the roots

Five different types of hydroponic set-up's

Let’s explore different types of hydroponic techniques. We'll look at how they work and the pros and cons.

1. Media bed
2. Nutrient Film Technique (NFT)
3. Deep Water Culture (DWC)
4. Vertical Production
5. Aeroponic Production

Media bed

Media beds are the most conventional form of hydroponic growing. You take a growing bed and replace the soil with another - inert - medium. A medium can be clay pebbles, rockwool, or some other aggregate, and the plants will grow roots into that bed. 

Rock-wool has better water absorption properties, and clay pebbles drain very well. Both mediums are suitable for root growth, and you can reuse them. Clay pebbles work well with a constant flow, rockwool works excellent with a timed water supply, or irrigate the hydroton clay pebbles continuously with a drip. The removal of water is essential to keep the media aerated. 

It is an easy starting point for people looking into hydroponics. But cleaning the beds and getting rid of the media takes effort, particularly if it decomposes and gets anaerobic. Because of this, people started to look at other techniques.

Pros:

• Easy starting point for people with existing beds

Cons:

• Cleaning takes effort
• Unwanted decomposition can cause problems for your plants

A variant of this method is using Ebb and Flow. With Ebb and Flow, plants get watered from below for a set amount of time. It also helps to recycle nutrients. The plant and medium will get some time to absorb the solution, and then the excess is drained off. Usually, plants can receive a flow of 5 to 15 minutes of high water levels. After that, a more extended period of Ebb, without a nutrient solution on the roots. 

Ebb and flow require more plumbing to control the water height, and planting young plants require planning. The roots need to get in contact with the water. However, it is easy to move the plants around in their pots. Ebb and flow are great for experienced growers with reasonable control of their nutrient solution as it's easy to measure differences in pH and EC between every flooding. 

Nutrient film technique.

Nutrient film technique, or NFT,  is a gutter with a cover or a PVC tube with holes. The plants are placed in the plug holes and grow out on the top side. The roots go down the trough. The trough can be long and sometimes has an incline of around 5 degrees. The grower can use a pump to pump the water with the nutrient solution to the top, and it will flow down naturally. Since NFT uses a thin film of water with nutrients, it is imperative to keep the water moving. If the water stops moving, your plants will experience drought. You might also consider using two pumps, just in case one breaks down. 

Inside the gutter or PVC-pipe, the interior is humid, and it is excellent to keep the roots oxygenated. If it is well insulated, it only takes small amounts of energy to influence the root zone temperature. If it is not well-insulated, the temperature can shoot up, especially during the daytime, and temperature swings can be bad for the plant roots. High temperature means less oxygen in the root zone. Also, if you use organic matter which accumulates on the roots, they decompose during hot temperatures. It is the reason why it is not so popular in tropical environments. NFT is a widely used technique elsewhere, and it is inexpensive. You can use NFT for lettuce and basil.

Pros:

• It's inexpensive to set up.
• Use less water and good nutrient control

Cons:

• Root temperature and cleaning are things to watch out for

Deep water culture (DWC) 

In deep water culture, the plants are in net-pots filled with a medium such as clay pebbles. The pebbles add oxygen to prevent roots' suffocation, and the water contains enough nutrients for the plant. Each plant can have an individual unit like a bucket or grow several plants in the same container. The size of the container determines the buffer capacity for the system. A bigger system leads to a more stable temperature (because of its large thermal mass), pH, and EC, but a disadvantage is that they require a lot more water and consume more energy to keep the temperature in check. DWC can be suitable for places with high daytime temperatures and cooler nights. The buffering capacity from the high volume of water slows down considerable shifts in temperature.

In lettuce farms, they use styrofoam boards to place plants. The board or raft is floating, and the plants grow out of the top of the raft. The roots dangle in the water tank below.

A DWC system allows you to grow small plants close together and placing them in another styrofoam board when they grow-up. In this way, you can optimize for space, making it more efficient. 

Plant roots consume oxygen, so for DWC, it is essential to aerate. Aeration prevents disease, plant stress, and root death. If you are growing in large tanks, you might want to add multiple pumps to make sure there is a backup to aerate plants; otherwise, you might lose a whole batch if the pump fails. You can add oxygen by using a venturi-type air inlet on the circulation pump or use air pumps.

Pros:

• It stabilizes root zone temperatures and suitable in tropical areas. 
• It's inexpensive to set up.

Cons:

• You have to aerate it to keep it aerobic.
• It requires a lot of water and space

Grow towers

Grow towers are NFT towers that grow plants vertically with plants growing out of the tower. Some towers grow on all sides, and others grow only out on the front. The main benefit is that it can save a lot of space compared to the other methods. You might have a grow tower on your balcony or in your spare room and still have space to move around.  

Inside the towers, there is often a film of nutrients that runs from top to bottom. Towers can contain media that helps plants with anchoring. 

If your tower has plant holes on all sides, you should need grow-lighting on every side to make sure all your plants receive enough light.

Pros:

• It saves space and is suitable for home-growers.
• It's inexpensive to set up.

Cons:

• The installation of uniform lighting can be more complicated if 360degree plant holes

Aeroponic production

The most high-tech solution is aeroponics. Aeroponics are technically quite complex and not suitable for beginners. They use a mist of nutrient solution. Growers place the plants in holes with neoprene disks. Net-pots don't work because they allow the nutrient mist to escape out of the tank. 

The misting nozzles water the plants. These are high-pressure pipes that actively form a mist of nutrient solution spraying on the plant's roots. The water must become superfine to get good coverage. This system's benefit is that it saves a lot of water and weight, enabling you to grow much taller vertical farms or grow in space. This system can also control the root climate and nutrient supply well. But the roots are delicate, and the nozzles must stay clean. The water spray must be in superfine droplets. Otherwise, you don't get good coverage, and with high pressure, you could damage the roots, which can be delicate. Overall this system is more complicated and increases the risk of system failure. In case of a pump failure, the roots dry out very quickly. 

The pros:

• It's light-weight and saves water
• It enables you to grow a lot taller per sq. meter
• It's not super expensive, except for the plumbing components

The cons:

• It requires a high level of root zone environmental controls that quickly become expensive.
• It requires perfect technical set-up and preventative inspections.  
• A small failure can lead to significant problems

If you still like to consider this, make sure you familiar with best practices to make it work.

Conclusion

These are the main hydroponic methods, and there are lots of other variants out there. Feel free to do more research, make some trial installations to see what works for you, and enjoy learning and growing with different hydroponic techniques. 

5. Hydroponic Measurement and Management

Keynotes:

• Electrical conductivity (EC) is a measure of salt in your solution and is used to measure the nutrients
• pH is a measure of acidity, and plants take in nutrients in certain pH ranges
• The temperature has a strong relation with photosynthesis and also influences other growth factors such as EC, TDS, DO
• Cooler water temperature can contain more dissolved oxygen (DO)
• Total Dissolved Solids (TDS) is another important measurement, especially in areas with hard water

There are five things you need to understand before running and managing a hydroponic system:

1. Electrical conductivity, or EC
2. pH
3. Temperature
4. Dissolved oxygen
5. Hardness and total dissolved solids

This is a quick introduction after this part is more about how to manage your system.

Electrical conductivity (EC)

Electrical conductivity (EC) measures salts and gives you an idea of the number of available nutrients in your solution.

Pure or distilled water has no electrical conductivity as it contains no minerals. When you add minerals to water, the dissolved salts allow the water to conduct electricity. The higher the concentration of salts, the higher the electrical conductivity. You can measure EC in siemens per square meter per mole (S/m2/mole) or millisiemens per centimeter (mS/cm).

Measuring this tells you how many nutrients there are in the water. For most plants, you want EC between 1.2-1.6 during the vegetative stage and 1.6-2.4 during flowering. The EC value that you need also depends on the type of plant that's growing.

Differences in EC over time tell you how the plants absorb fertilizer and when you need to add more.

pH is a measure of acidity

pH affects the availability and absorption of several of the 16 atomic elements needed for plant growth.

pH is a measure of acidity, a negative logarithmic measure of hydronium ions. Since pH is logarithmic, a pH of 4 has ten times as many hydronium ions as a pH 5, and pH 3 has ten times as many hydronium ions as a pH 4. It's not a linear scale.

An important thing to understand about pH is that it impacts your plants' solubility and availability of different nutrients. Each plant type takes up nutrients in different pH ranges, and certain nutrients are only available in specific pH ranges.

The goal is to find the perfect range where almost everything is available to some degree and keep within that range to ensure that the plants are getting what they need.

pH is a fundamental measurement that you will use in hydroponic systems.

Temperature affects other measurements

Temperature is relevant not just for our crops but also to understand EC, TDS, DO, and more. Temperature also has a relationship with lighting. With higher temperatures, you are generally able to provide more light for photosynthesis. 

Different plants like different temperatures both for shoots and roots, so measure both and regularly. EC meters take temperature as well because EC is strongly dependent on the temperature of the solution.

Dissolved oxygen (DO) is necessary to plant health

Dissolved oxygen (DO) is the amount of oxygen that is available in the water. DO is usually measured in milligrams per liter or parts per million.

In hydroponics, there must be enough oxygen dissolved in the water because it's the only way how roots are going to get oxygen for healthy growth and respiration. Low levels of oxygen in your solution are suboptimal. Some people might say, "plants produce oxygen in the process of photosynthesis, so I don't need to give oxygen.". Unfortunately, that is not correct.

Plants produce oxygen, especially during the daytime when they photosynthesize. But at night and especially in the roots, they are consuming oxygen. Some plants can transport oxygen to the roots but are rare, so you need to supply roots with high oxygen levels. 

In aquatic systems, dissolved oxygen is a fundamental measurement. Dissolved oxygen is dependent on temperature; it's less soluble at high temperatures and more soluble at low temperatures. If your system is consuming a lot of oxygen, running your temperatures a little bit lower can help.

Total Dissolved Solids (TDS)

TDS is enabling you to measure hardness, pollutants, and other solids dissolved in your solution. TDS is not crucial if you're using a reverse osmosis (RO) filter because you just don't have many organic solids dissolved in your solution. An RO filter makes water less hard; it removes minerals and carbonates that cause hard water. 

6. Hydroponic Grow Lighting

Using HortiPower grow lights

Keynotes

Lighting helps plants with growth and development.

Natural daylight is changing all the time and gives plants a variety of light that they need.

During the day, photosynthesis accumulates sugar and supports growth. During the night, plants rest and respire.

Plants see the light differently than humans and need different light

The right type of light at the right time helps plants to grow well

Micromole (μmol/s) is the unit for light for plants.

Lumen is the unit for light used for humans. 

Lightscripts for plants can recreate optimum growth conditions for photomorphogenesis and photosynthesis

Light is essential for plant growth

Light is the critical driver for the growth of all crops. Natural daylight has a unique spectrum and varies between seasons, different times of the day, or geolocation.

A part of this daylight is visible for the human eye, e.g., in 380-780nm, this is visible light. You can measure visible light in lumens. And the amount of light on a surface is measured in lux.

The photosynthesis of plants is not related to visible light. It is related to photons that are absorbed through plant photoreceptors. This plant-centric light ranges from 350-800nm. You can measure plant-centric light in micromole or μmol/s. The amount of light that falls on a plant leaf is measured in μmol/m2/s. 

The human eye perceives light very well in the green-yellow part of the spectrum, and this is why traditional light sources and HPS lights often have an orange glow. However, plants need a lot more red and blue.

With the rise of LEDs, you can add specific light in specific wavelengths to support photosynthesis and growth.

Photosynthesis and Photomorphogenesis

Light drives plant growth and development through photosynthesis and photomorphogenesis. Photosynthesis happens in the plant leaves. CO2 enters through the stomata, and with the energy from sunlight, the plant can make sugars which helps plants grow. In this process, plants release oxygen.

Light intensity has a relationship with the photosynthesis curve. If there is too little light available, the plant has not enough photosynthesis to grow. With increasing light, photosynthesis increases almost in a linear way to 200-300umol. With higher light intensities, the photosynthesis decreases to a maximum level. Note that if you grow at really bright light levels, you will also need to add CO2.

Photomorphogenesis is a process in which light provides a signal or trigger to the plant. It acts as a biochemical signal. Photoreceptors are molecules that respond to specific light colors. Example photoreceptors are phytochrome, cryptochrome, phototropin. These photoreceptors have different functions. Phytochrome can trigger a shade avoidance response and the germination of seeds. Growers can use light to, e.g., elongate plants, stimulate flowering, or delay flowering so you’ll get more robust plants.

Light colors

UV light

UV light: UV is light in-between 100-400nm. There are three types of UV: UVA 320-400nm, UVB 280-315nm, and UVC 100-280nm. UVC is absorbed through the ozone layer and does not reach the earth. UVC is, in some cases, used to disinfect bacteria and viruses. It is harmful to the human body as well. UVB can, at low intensity and short periods, increase the plant immune system against pathogens. It can also lead to less leaf surface and less biomass.

Currently, UV is not used for growth and development for plants, although some growers are experimenting with it. UV is harmful to humans, and you won't see it clearly by the human eye. Hence, we don’t recommend embedding UV light in a regular light fixture.

Blue light

Blue light is light in-between 400-500nm. It is an essential color for LED plant-lighting. Combined with red light is can improve plant growth. Hence early generation light fixtures contained red and blue LEDs. Blue supports more chlorophyll, and carotenoids which can help to increase the photosynthesis speed. Another effect of blue light is the simulation of phototropism. Blue light can also help to increase the compactness of the plant. The exact amount of blue light you need depends on the crop, season, and other light. More light is not always better. It is about the right amount of light at the right time. HortiPower lightscripts help you with the optimum settings for your crop. If you prefer something more straightforward, you can use the fixed spectrum fixtures of HortiPower for specific crops and applications.

Green light

Green light is in-between 500-600nm. Green light can influence the closing of the stomata. Some people assume that plants fully reflect green light. This assumption is not correct. Green leaves can also absorb 70% or more of green light. Green light can also penetrate deeper into the leaf, supporting photosynthesis when there is little blue and red light. Carotenoids mainly absorb green light, and they, in turn, can transfer energy to chlorophyll. This indirect transfer is also a reason why green light has a lower photosynthesis efficiency than red light. HortiPower recommends having some green light. In particular, when red and blue are the primary colors. And with thick crops with multiple layers of leaves, green light can support a better light distribution in the plant and higher photosynthesis.

Red light

Red light is at the 600-700nm wavelength. It is one of the essential colors in grow light. They are very efficient in stimulating photosynthesis. The absorption peaks of chlorophyll a and b are in this area. Red light can stimulate the germination of seeds, develop leaves, increase photosynthesis, and support or delay flowering. Note that red light for plants is different than red light for humans. In standard color-changing architectural lights, red light is at 630nm. For plants, this is not suitable, and HortiPower uses 660nm red light, which is also called deep red. Aside from deep red, there is also far-red light in the 700-800nm range. Optimizing the peak wavelength of red light is significant because not all red light yields the same result.

Far-red light

In the late afternoon, the natural daylight contains relatively more far-red. And this high far-red ratio is amplified by plants themselves. Plants absorb red light, and they mainly reflect and let-through far-red. It means that the ratio or relative percentage of far-red can vary widely during the day. Plants that are in the shadow of other plants can experience a lot more far-red too. Fa-red can trigger a shade avoidance response. Plants start to elongate to reach better light. The grower does not always desire elongation since it can make the plants thin. Far-red light can support rooting and fruiting.

Lighting as the sole source of indoor cultivation

You can fully grow indoors with hydroponic shelves or grow-tents, but you must have the right lighting. On shelves and grow-tents, there is little or no-natural lighting. HortiPower lights help you to grow indoors. There are different lamps and fixtures, depending on whether you grow in the vertical farm, grow-tent, or greenhouse.

The right light intensity and optimized spectrum will help your plants to grow. Compared to traditional grow-lighting, LEDs are very efficient. LED lighting provides significant energy savings. It can save up to 50% energy compared to a conventional light. Also, LEDs can be made at a specific wavelength, giving much more control on the type of plant-centric light you as a grower can provide.

HortiPower has fixtures that can control the brightness/ intensities. The flexible spectrum fixtures can also adjust the spectrum and provide the right light at the right time. It helps you to get the best yield all-year-round.

Aside from the energy-saving, you will also be able to optimize and increase:

• Production per plant
• Production from the same square meter
• The speed of the growth cycles (e.g., 21 days for lettuce instead of 25-100 days)
• Predictability of growth, regardless of the weather
• Cooling needed
• Quality (better taste)
• Consistency of crop

Lightscripts

Lightscripts are optimum light instructions based on your grower goals, plant needs, and growth environment. They take the following into account:

Lighting characteristics

• Light intensity

• Light spectrum

• Light / Dark

• Sum over time, moment, ratio, direction, distribution over plants

Environmental conditions

• Temperature
• CO2
• Water
• Growth medium, nutrition, plant hormones

 Plants Varieties/Species

• Growth stage
• Way of growing

Part 2: Management of Hydroponic Systems

Keynotes:

• EC is Electrical Conductivity, and it is a key measurement in hydroponics.
• PPM and mS/cm expresses the EC value
• Refresh your solution regularly to avoid toxicity
• Tap water has EC value but often without nutritional value 
• EC influences the ability of a plant to take in water, don't get your EC too high
• Building up the plant internal EC will help to boost growth
• Sometimes the EC value in the substrate increases due to water evaporation

1. EC

EC is Electrical Conductivity, and it is a key measurement in hydroponics.

You can measure EC in two ways: the first method is by parts per million (PPM) and the second as μS/cm2 (microsiemens per centimeter) abbreviated as simply μS and also mS/cm2 (millisiemens) abbreviated as simply mS. The ideal PPM depends on the crop that you are growing. It can vary from, e.g., 560 PPM for lettuce to 2450 PPM for crops like tomatoes. In mS/cm it would be about .8 – 3.5+ mS/cm.

EC measures the electrical conductivity, and more salty water is more conductive. E.g., fresh rainwater has a conductivity of 0, but seawater has a much higher conductivity because they contain more ions (salts). Note that EC will not tell you what salts are in the water. Therefore some growers prefer to use a filter to start with a clean slate and then add the desired nutrients. Alternatively, you can measure the EC of your freshwater source and then measure it again after adding your solution to understand what EC is related to your nutrients.

Should you use PPM or mS/cm to measure EC?

Typically, a ppm meter measures the EC of a solution in μS/cm2 (microsiemens) and then converts it into PPM. However, not all factories use the same conversation rates, and therefore EC is preferred as it is more accurate.

PPM is also used to measure the total dissolved solids (TDS), and using PPM to describe the measurement of both EC and TDS is confusing.

There are different brands and options, such as the truncheon meter from BlueLab. Truncheon meters are hand-held analog meters. You can also get a digital meter or get one connected to an app.  

Make sure you clean your meter and calibrate it regularly. You can get special conductivity standard bottles to calibrate your meter so you'll have accurate readings. 

Measure EC regularly, for example, every day. This data allows you to take action as soon as possible. 

If your EC measurement is the same every time, it means the plant uses as much water as nutrients. You can top up with nutrients in the same solution as you gave before. 

If the EC goes down, it tells you that plants are using more nutrients than water. You can consider providing a slightly stronger solution and see how your plants respond to that.

If the EC goes down, it means the plants are using more water, and you're perhaps over-feeding the plants. The next time you add solution, you should add more water, so the solution is thinner. Other signs of over-feeding are burned leaf tips and slowed growth. Note that hot days can cause plants to take up more water, and they take in more nutrients as a result of that, so if there is an incidental hot day, you could choose to lower the EC value, and your plants will be fine.

Refresh your solution regularly 

Make sure you refresh your solution entirely once in a while (e.g., every seven days) as well. EC is a measurement of the saltiness, but it doesn't tell you the amount of the individual elements, so you can have perfect EC measurements and still have nutrient deficiencies. A complete refresh of your solution reduces the risk of toxic nutrient levels.

Does tap water with EC value have nutritional value? 

You might like to measure the EC of your source water supply. Usually, the EC and other mineral counts of your source water will be close to zero. For example, tap water can contain sodium and chloride, which has EC value, but no nutritional value for the plant.

EC and plant water uptake 

The EC value influences the plant's ability to take in water and bring it into the shoots and leaves.

Perhaps you are familiar with dehumidifiers that use salt to reduce atmospheric humidity. This principle works since salt can attract water to itself. In a solution in a hydroponic system, it works in the same way. The salts will draw more water, i.e., water moves to the area of higher salt concentration. This difference is called water potential gradient and it involves osmosis.

Osmosis is a semi-permeable membrane that allows water molecules to pass through but restricts the ions or salts' movement in solution. Molecules typically move from areas of lower concentration to areas of higher concentration. 

For the plant to draw water out of the solution, there has to be osmotic potential; i.e., the concentration of ions inside the root is higher than ions outside of the root (read ions in the solution). 

If you have many nutrients in the water (which results in high EC), the salt attracts water to itself. High EC makes it difficult for the roots to take in water and use it in the shoots/ leaves. If the EC is too high, the difference between the two concentrations won't be big enough for osmosis to take place, and the plant will fail to take up water. In this case, it is called drought stress. Water is vital for plants to cool themselves through transpiration (evaporation) which they need, especially during the daytime when heat and light are present.

Some growers use drought stress as a tool to, e.g., increase the sugar content in tomatoes, but this requires more advanced nutrient and sensor systems.

Internal EC and nutritional needs

If you're using plant cuttings, a higher EC in the plug can draw the water out of the stems. Therefore at the beginning of the growth process, you'll generally start with a lower level of nutrients and increase them as plants build up EC internally as they grow. Building up the EC is essential because as plants grow, the osmotic value falls. Within the plant, the salts redistribute, and the plant can quickly start to wilt or dehydrate. More nutrition to the roots will help plant growth. Even when the water evaporates, the salt remains in the plant, raising its internal EC value (osmotic value). Now you can increase the EC value in the solution again and therefore supporting plant growth. When plants become bigger, they also need more nutrition. Some of this nutrition converts into oils, fats, and so forth, but some nutrients remain in the plant's sap and determine its internal EC. 

The EC value in the substrate might increase due to evaporation

The goal of fertilization is to supply the right nutritional elements to the plant. In general, you should lower EC in the final plant growth stage after its vegetative stage. 

If you have a system that you can drain, you can rinse out the solution with a lower EC solution. If you have a non-drainable system, your nutrition is likely building up after multiple refillings. Water in the substrate will evaporate, but the salt will not. So, in this case, EC goes up, and you should add more water; otherwise, the EC value will rise dramatically. At some point, this will reach a level that slows down the plant's ability to take up water or even drain water from the plant. 

EC and Plants

1. Plants can consume nutrients at different rates.
2. Plants may take up more of one nutrient than another, leaving your solution unbalanced. The goal of adding nutrition is to match nutrient dosing to the plant's nutrition consumption. Plants need the right amount and right type of nutrition 
3. EC is an indicator for the fertilizer that is available for the plants
4. EC is also a climate control mechanism that influences water uptake from plants.
5. Plants should start growing with a low EC, and once they begin to grow, you can build up the EC to provide for the plant's nutritional requirements and raise the internal osmotic value to build a more vigorous plant.
6. The plant requires little nutrition in the weeks just before cultivation. Provide just enough nourishment to maintain the nutritional stock and keep the EC stable. You can also lower EC or even rinse your solution.
7. You can change the EC value in your solution by dosing and filtering, and understanding your source water.
8. Use fertilizers that are suitable for hydroponic systems. Do not use fertilizers made for soil. Use good-quality suppliers that have consistent quality fertilizers. 

2. pH

Keynotes:

• pH is a measure of how acid/ basic the water is 
• The recommended pH value depends on the crop and the type of nutrients
• you can measure pH in different ways
• pH up and pH down can adjust the pH value
• hard source water has a high pH, and to regulate hard source water, you have to use a reverse osmosis filter 

pH is a measure of how acid/ basic the water is                                              

pH stands for the power of hydrogen, and it is a measure of how acid/ basic the water is. In particular, the concentration of free ions H+ (hydrogen) and OH- (hydroxide) in your solution. It is relevant because it tells you about nutrient availability, the hardness of your source water, and much more. pH uses a logarithmic scale that ranges from 0-14. 

Distilled water has a pH of 7. It indicates neutral acidity. Neutral water means there is an equal concentration of H+ and OH-.

Battery acid has an acidity of close to 0. Acidic solutions contain many active hydrogen ions (H+) and few hydroxide ions (H-). 

In basic water, there are few hydrogen ions (H+) and many hydroxide ions (H-). In this scenario, most micronutrients will precipitate out of the solution, which means your plants cannot absorb them and suffer nutrient deficiencies.  

If you want a successful hydroponic system, you need to have the most beneficial pH value. Plants feed on dissolved nutrients in the solution at a beneficial pH value. The optimal pH value depends on the crop that you grow.

So nutrient availability is affected by pH. The acidity of the solution can often change the form of the nutrient. Some nutrients will cease to solute at a basic or acidic pH and precipitate, adhering to the tank's sides or falling to the bottom. 

Also, nutrient uptake by the plant requires a concentration gradient of ions. Ions move from an area of high concentration outside of the cell to low concentration inside the cell. Without the ions, it would not work.

Recommended pH values

Some charts show the nutrient availability through the pH scale. Look at this chart, and you'll see what nutrient is available to plants at a different pH range. If you know your crops and the nutrients they need most, then you can run the system that grows those plants at a pH that allows the crop to take up that nutrient. Usually, this sweet spot ends up being between 5.6 or 5.8 and 6.2 or 6.4.

If the pH levels are outside the optimum range, plants will lose the ability to absorb some of the elements they need for optimum growth.

The optimum pH level varies. Most crops prefer a slightly acidic solution.

How to measure pH

There are a few methods to test pH.

The first one is a paper pH test kit or strip. The paper has small strips of different pH-sensitive dyes known as litmus, hence the term 'litmus test'. You can dip this strip in your solution, and the color chart will show you the corresponding pH level. These kits are disposable and inexpensive. You can probably buy them at any pet store (to measure aquarium water), but it is sometimes hard to judge the precise pH level. 

Liquid pH kits are also inexpensive and easy to use. With these kits, you place a small amount of your solution in a small tube, add few drops of the liquid testing solution and shake it. You can then compare the color to the chart.

pH meters are a bit more expensive, but it is a fast and convenient way to measure pH. You dip the meter in your nutrient solution, and the pH level shows on the display. You need to make sure you clean these meters and calibrate the electrodes so your reading will be correct.

How to adjust pH?

Auto-dosing equipment would be the easiest way to manage pH. Alternatively, you can adjust pH using pH up and pH down in either liquid or dry form. 

The pH up contains potassium, calcium, or magnesium hydroxide, and pH Down usually contains phosphoric or nitric acid.

Adjust the pH gradually and avoid sudden changes in the growing environment. Rapid changes in the growth environment cause stress for plants.

pH and hard source water

if you are using hard source water, it tends to have a higher pH, and if you try to adjust it with pH down, it is likely to jump back up. you could try to reduce the hardness of the water by reverse osmosis or filtration.

3. Source Water Quality

Keynotes:

• Your freshwater source is essential, and you need to know what it is in 
• Source water can include pollutants, bacteria, and minerals
• You can test your source water or check out test reports from your local water supplier
• You can use an RO filter or sterilization to get to pure water, which is safe and clean for hydroponics

Water is an essential element

Water is essential in a healthy hydroponic system. 

Ideally, you would start with pure water and then mixing it with the nutrient solution in the precise ratio's that your plant would like. However, most likely, you will use tap water, but it can contain chemicals or minerals, which is suboptimal for plants.

What can be in the water?

There can be pollutants, bacteria, or minerals in your water. 

Pollutants

Pollutants can harm your crop. Examples are, e.g., nitrates or chlorine. Chlorine is a toxic gas, and it acts as a disinfectant and prevents the spread of disease. It makes sure tap water is safe to drink, and while it may be safe to drink for humans, it can be toxic for your plants. If you are using soil, the chlorine can be removed when the water moves through the earth. In hydroponics, you don’t use soil. But you can expose water to the sun, and leaving it for 12-14 hours will reduce chlorine levels through evaporation. 

You can get more information on pollutants in your water through a municipal water report. Note that the piping system for your water to your place or building can also add other things such as copper, lead, or other organic material to your water. 

Bacteria

Bacteria can be another issue. There can be hundreds of types of non-fecal coliform bacterial in the air and water and fecal coliform. The vast majority of these coliforms are harmless. But testing for fecal coliform or testing for bacteria that occur in feces is an important test because of the impact that fecal coliform could have on human health. Foodborne illnesses from fresh produce can arise from water or sanitation, so you'll want to take of this.

Minerals 

Minerals such as calcium, magnesium may be present in the source water, including sodium or metals and metal oxides

Testing

For freshwater, your municipality or water supplier will have test reports. These reports cover the most critical elements. This data can be quite regional, depending on the primary source of the freshwater. 

You can also get the water tested in a 3rd party lab, and if you're GAP certified in the USA, you might need the 3rd party report anyway. 

Based on the findings of the test report, you can consider your options to, e.g.:

• Getting a different water source
• Using RO filter (for carbonates and salts)
• Sterilize water

4. Temperature

Keynotes:

• Temperature is essential in hydroponics, and it influences pH, EC, and photosynthesis. It can also influence the spread of pathogens and pests
• Photosynthesis occurs within a certain temperature range
• The temperature should follow a daytime/night-time. Avoid huge temperature swings as well as extreme heat or ultra-low temperatures
• Roots/ water temperature can differ from the ambient temperature. Keep the water temperature stable. 
• If you're using HID lights, you need to take care of ventilation and avoid heat built-up. LEDs generate a little bit of heat.
• You can manage the water temperatures using chilling, heating, and flow volumes
• Keep an eye on storage temperatures

Temperature in Hydroponics

Getting the right temperature is essential in hydroponics. It can influence pH, EC, photosynthesis rate and encourage or discourage pathogens and pests.

The temperature you need is different for ambient temperature (air) or your solution temperature (water) and the plant's root zone. It will also differ from day to night.

Hydroponic ambient temperature

Photosynthesis occurs within a specific temperature range. When you have the right temperature, your plants can grow better. If your temperature is too high, the plants will lose water quickly. Small pores on the leaves (stomata) allow transpiration and enable the plant to cool down. In case the room is too hot, plants can also close the stomata to conserve water. When plants close the stomata, water traps in the plant leaves, and this can cause internal cell and enzyme damage. It will result in poor growth and unhealthy plants, and they have difficulty growing into healthy and vigorous plants. Another consequence of high temperatures is that the plants consume a lot more water; thus, they may also take too much nutrition, which can cause over-fertilization.

Ambient temperature influences humidity as well and, therefore, the overall growth environment. Generally, with high temperatures, you would need a high humidity room.

Temperature and photosynthesis

Your plants are processing energy 24 hours a day. During the daytime, they make and store sugars, and at night they rest, respire and transport sugars throughout your plants. The speed at which this happens is directly related to temperature. It is beneficial for your plant to decrease the temperature a bit a night so they'll have a cool/resting period.

Plant roots/water temperatures

Water temperatures are separate from air temperatures and crucial to maintaining stable root zones temperatures. Shoots and roots can differ in the ideal temperature range, and you can separate ambient/ air temperatures and water temperatures separately. If you can manage your solution's temperature, you will have much more control over your growth.

It would be best to keep the water temperature and the root zone temperature stable, minimizing temperature swings. Stable temperatures support optimum growth and avoid mold, mildew, stagnant growth, or dismal yields.

If your air temperature is very hot, you could keep your water a bit cooler, reducing your plants' stress.

A lower water temperature will also help to enlarge the dissolved oxygen capacity of the water. The higher the temperature, the less oxygen can stay in the solution, and the oxygen is essential for the roots. Another issue with warm water is that it is much easier to become a breeding ground for unwelcome bacteria and fungus. 

Too cold water is not helpful either. If the water is too cold, plants may shut down and not take in the nutrients they need. You can use a water chiller or evaporative cooling. If the air temperature is very cold, you warm up your solution. You could use water heaters or other methods.

Flow volumes will help you control water temperatures. For example, if your PVC of NFT is a bit thicker and you increase the water flow speed, it can help to keep the temperature inside stable. If the ambient temperature outside is a bit cold, you can raise your solution's temperature and keep your plants growing well. Likewise, in warm weather, you can help plants to cool a bit with a lower solution temperature than the ambient temperature. 

Controlling ambient heat

Managing the ambient temperature depends on whether you use a grow tent or use a room in a building for growing. 

If you are growing in rooms or buildings, you'll need to manage the whole room's temperature or facility. Buildings can have excellent insulation, floor heating, and cooling, keeping your ambient temperature perfect. Alternatively, you can also grow in grow-tents and manage the climate in the tent. It might be a more energy-efficient option if you're growing on a smaller scale.

In grow-rooms, the use of grow-lights can generate heat, especially with HID or any gas-based lighting. In these traditional light sources, both the light-beam (downward heat) is hot and the fixture or power-supply (upward heat).

LEDs will dissipate heat on the printed circuit board (PCB) and heatsink/ fixture. The light-beam itself is cold in LED grow lights. Most modern grow lights use passive cooling, which means they will need airflow to cool down. 

Especially if you are using HID lights, you might have heat built-up under the lights. Use oscillating fans to move the warm air under the lighting away from the plants and mix it with cooler air in the rest of the room.

If your growing environment is too hot, you could remove the hot air with an inline extractor fan. This fan can take hot air and duct it out of the room. It would be best if you placed this extractor fan at the top of your room since heat always goes upwards. If you are removing hot air, you also need to supply the room with fresh and cooler air. You could do this with another inline fan to pump fresh air into your room. If you are using only one extractor fan to air in and out through its vents, it will not be effective in bringing temperatures down.

Some fans have a thermostatic fan speed controller. With this, you can set a maximum temperature, and fans can adjust their speed to move more air. Likewise, as the temperature decreases, so does the fan's speed. Thermostatic fan speed controllers are the right choice for summers where the outside temperature varies from day-to-day.

If your grow room temperature is always high, you may want to invest in an air conditioner. Air conditioners are an effective way to bring the ambient temperature down. Note that air conditioners also remove water from the air which means a lowering humidity. A humidifier can help when the air is too dry.

Temperature meter

You can measure temperature with a thermometer. To measure the night and day temperature, you need a max-min thermometer. It allows you to monitor the hottest and coolest temperatures in your grow room over a twenty-four-hour period.

The ideal place for a thermometer is half-way up your grow room and out of direct light. If the air in your grow room is well mixed, your thermometer will be reading an accurate temperature. You should try and keep your night and day temperatures close to each other for fast vegetative growth. To promote flowering and fruiting, you might need to increase the difference between night and day, depending on the crop. But if your temperature difference goes beyond six °C, you'll put your plant under stress.

When ambient temperatures are very high, you should get a lower water temperature. When the ambient air temperature is low, you should aim for a higher water temperature

Water heaters

Water heaters help you to manage the water temperature. These heaters are fully submersible, and you can install them in your solution/ reservoir tank. They will heat the water to the desired temperature and then turn-off once they reached a target temperature. 

The capacity you need depends on your tank's size and the temperature difference between the target temperature and the starting temperature. Place the heater near the inflow or outflow of water so the temperature is well circulated. Choose a heater with some overcapacity.

Water chillers

Chillers are rated in horsepower (HP) and flow rate with either gallon per hour (GPH) or liter per hour (L/hr). Choose a chiller with a bit of overcapacity.

The storage temperature of nutrients and seeds

Note that nutrients and seeds often have a recommended storage temperature. E.g., between 18 C and 21 C and away from direct sunlight. If it gets very cold, e.g., below 5 C, then crystallization can occur, making the product useless. Too high storage temperatures can cause seed deterioration. It lowers the seed quality and reduces the germination percentage of the seed.

5. Filtration, Sanitation, Sterilization

Keynotes:

• You can filter mechanically or biologically or a combination of both
• For mechanical filtration, you can measure pre-entry or in-system
• Solids can cause clogging, fouling, pathogens, and cause problems with your water quality 
• Canisters and bead filters can help to filter solids 
• Sanitation is cleaning your facility and the surroundings of your growth system
• Sterilization neutralizes both good and bad organism 
• There are three types of sterilization; UV sterilization, chemical sterilization, and heat sterilization.

You must keep your hydroponic system clean. Because water is such an essential element in hydroponics, the risk for water-borne pathogens and algae is real. On the upside, there is less risk for fungal foliar diseases compared with greenhouses. Prevention is the best cure, and you can use filtration, sanitation, and sterilization to mitigate risks.

A filtration system helps you to reduce the likelihood of disease in a hydroponic crop. Your system can be kept cleaner for a more extended period with less maintenance. 

Filtration can remove solid matter.

In mechanical filters, you'll run water through a filter device that removes the solid matter.

There are two main approaches for filtration.

Entry filtration. Rubbish in is rubbish out, so entry filtration will happen before the source water enters the system. Examples are reverse osmosis systems that filter micron sediment, remove chlorine with carbon cartridges, chloramine, and organic pollutants, and extract minerals, salts, and heavy metals. All these entry filtrations can influence EC, Total Dissolved Solids (TDS), and pH. 

System filtration. System filtration removes solids that are already in your system.

What solids do

Solids or organic matter can reduce the dissolved oxygen because it needs oxygen as they decompose. If you are using NFT and solids are stuck in root matter, it can kill plants quickly. The system will also be more vulnerable to pathogens.

Solids can also cause clogging of nozzles or drip systems and cause fouling in pipes and tubes.

There are different types of filters to filter solids

Canister filters remove the water from the tank through an intake tube or valve, and the water goes through filter media in a pressurized canister; the filtered water is then pumped back into the tank via spill-way or spray bar. They are inexpensive and easy to install.

Bead filters are closed (pressure) vessels, and they contain thousands of plastic beads. Water presses through a layer of beads. Bacteria attach themselves to the beads and break down harmful substances such as ammonium, nitrite, and nitrate. This filter is hence a combination of mechanical and biological filtration.

Sanitize your system and environment

Sanitation helps you to deal with pathogens, such as Pythium and Fusarium, algae, and insects.

Pythium and Fusarium travel through water, so keeping your system clean, including clean from dead plant debris, is essential.

Algae thrive in oxygenated and fertilized water. They can harbor pests and deplete the dissolved oxygen levels in the water. Algae grow in layers, so scrubbing is very useful in removing algae. 

All contact surfaces and equipment that encounter water or plant material should be washed, disinfected, and rinsed. Only rinsing may still leave organic matter behind, resulting in an infection for the next crop. Dead plant tissue can host pathogens.

If you like to be GAP certified, you need three sanitation approaches

Mechanical sanitation includes physical work such as scrubbing. You should also consider how your produce is grown and moves throughout your space from seedling to consumable produce.

Chemical sanitation includes disinfection with, e.g., unscented bleach washes, soaps, food-grade hydrogen peroxide, isopropyl alcohol, and other chemical material. 

Cultural sanitation includes habits such as sterilizing tools to remove spores or eggs, rinsing feet, using PPE, etc. Ensure you also take care of your safety, especially in working with cleaning agents, to make sure you follow the usage and safety instructions.

Sterilization helps to neutralize all microorganisms 

Sterilization does not differentiate between beneficial or harmful organisms, so take note of this. 

UV sterilization

At a certain intensity and duration, UV light can destroy organisms' DNA structure and fecal coliform. Sterilizers may have a UV light bulb inside, the water flows past the UV light, and the UV makes the water sterile. Note that UV is neutralizing microorganisms, but it does not filter particles or matter. You can use a UV sterilizer to make sure that the water that enters your system is sterile.

Chemical sterilization

Chemical sterilization is the use of chemicals or solutions such as bleach and hydrogen peroxide. They can also impact plant health, so make sure you rinse your system after sterilization.

Heat sterilization

Heat sterilization or steaming is perhaps the most traditional technique. It is so hot that it kills everything. 

6. Meeting Crop Needs

Keynotes:

There are three main areas to monitor and manage for the health and wellbeing of your crops. 

• Nutrients / solution
• Growth environment
• System

The hydroponic system should be set-up and managed in such a way that it allows the crops to reach potential production and can grow in an optimum way. 

There are three main areas to manage for your crops

1. Nutrients/ solution. Crops need nutrients to grow well. You need to understand what the crop needs, how to measure your nutrients, what you can do in case of deficiencies, and tailoring to specific crops. You'll also need to monitor pH and EC.
2. Growth Environment. The growth environment includes parameters that you can optimize so that plants feel happy and grow well. Lighting, temperature, and airflow are essential for indoor cultivation.
3. System. You need to build and monitor your system and get something that meets your crop's needs, is designed around your skillset, fits in your local environment, and is economically viable.

Part 3: Hydroponic Nutrient Management

1. Fertilizers

Keynotes:

• Dry fertilizers are cheap and suitable for large scale hydroponics
• Liquid fertilizers are easy to use but expensive 
• When choosing between a liquid vs. dry fertilizer, it's imperative to consider the cost of shipping
• Your fertilizer needs to be compatible with your labor goals, markets, certifications, equipment environment, and crops
• Supplementary fertilizers are kelp meal concentrate, chelated iron, magnesium sulfate, potassium hydroxide, and acids

There are two fertilizers to consider:

1. Dry
2. Liquid

Powder Fertilizer

Powder fertilizer or Dry fertilizer usually comes with three-core mixes that supply all the nutrients for your plants. They come in different ratios of different N-P-K ratios, and the one you need depends on the crop you are growing. Dry fertilizers are inexpensive, and you can use them in large-scale operations. 

The three core mixes:

Part I is the primary mix. It contains most of the micronutrients as well as Nitrogen, Phosphorus, and Potassium, or N-P-K. This part is typically very soluble and easy to mix

Part II is calcium nitrate

Part III is Magnesium sulfate (Epsom salt)

Oxygen, hydrogen, and carbon are pulled from the water and atmosphere. You don't need to worry about this. 

Liquid Concentrates

Liquid concentrates are very convenient and the right choice for small-scale systems and beginners. But they are expensive and typically not tailored for specific crops. 

Supplementary Fertilizers

Supplemental fertilizers help you to adjust pH and supplement a nutrient at the same time. There are five main supplements used:

1. Kelp meal concentrate is made from seaweed and is used to supplement potassium, and has many micronutrients. It is very environmentally friendly as well.
2. Chelated iron is an iron supplement for plants, and it makes sure the plant can absorb the iron. Note that you may need different supplements depending on the pH value. Iron-EDTA is soluble at low pH values. It is less effective at higher pH values. If you're using high pH, you can consider iron-DTPA that is effective up to 6.7 or 6.8. 
3. Magnesium sulfate or Epsom salt supplements are magnesium and sulfur it helps to resolve magnesium deficiencies in your system.
4. Potassium hydroxide can raise the pH level. 
5. Nitric acids or phosphoric acids can lower pH

Considerations in choosing your fertilizer

Shipping costs

Shipping-costs of fertilizer are big. Dry fertilizers save on shopping costs.

Dosing

The bigger the system, the more fertilizer you will be using (roughly), so you'll get more use out of dry fertilizer than you will liquid. 

Formulation

Choose a fertilizer-formulation that is suitable for your crop. 

Ease of use: how effortless is the fertilizer to mix? Will you be using a dosing system? 

Certification

If you're selling your food under a specific certification, you should check if there are any preferred solutions that you should use. 

Equipment

If you're using NFT, you cannot run high solid solutions in the system. 

Try out fertilizer and see what your crop does in your grow-environment. Each grower, crop, and growth environment is different. A test helps you to see what it does.

2. Mixing and Dosing

Keynotes:

• Mixing by hand is cheaper to start with, but it takes time, and you need to be consistent
• Automated mixing/dosing is more expensive upfront but reduces labor and avoids human error

The basics of mixing

It is easy to start with mixing by hand. But it requires you to be on-site in person, including during holidays and weekends. 

You can start with hand mixing to see how everything works and then switch to an auto-dosing system later on. If you're working in a team, make dosing guidelines, so everybody follows the same steps and amount.

How often should you dose?

Dose daily to keep the nutrient levels consistent. 

Automatic Dosing

Automatic dosing can help you to manage the nutrients for you. Sensors measure the EC, pH, and other water quality parameters. 

The computer can then analyze and add more or less solution via solenoids or pumps. The computer adds nutrients to your solution when it reaches a certain threshold. 

Auto-dosing will save you time, and you can program different EC and pH levels at different times of the day.

Auto-dosing systems can be quite expensive. You also need to make sure you keep the sensors clean. Otherwise, the sensors can provide wrong information to the computer, which can trigger overfeeding. 

There are also auto-dosing systems that work with notifications, so you'll still need to 'approve' the adjustment by your phone or email, but you'll have an accurate understanding of what went into your system and when.

3. Water and Tissue Analysis

Keynotes:

• You can analyze water as well as plant tissue to get accurate data
• Water/solution testing will tell you exactly what is in your water and what not
• Tissue analysis helps to analyze toxicity and deficiencies in plants 

Water and tissue analysis will help a lot, especially for first-time growers.

Water/Solution Analysis

A water/ solution analysis will give you an accurate and quantitative measurement of what is in your water and what is not. You'll be able to measure nutrients, metals, etc. You can also compare this to prior data or keep it as a reference in the future.

With this data, you can decide when to balance your solution or when to replace the solution. 

Tissue Analysis

Tissue analysis looks at tissue samples and checks for any toxicity or nutrient deficiencies in the tissue.

Inquire local universities or labs for more info. These tests can be expensive. You'll have to weigh the costs vs. the opportunity costs of not growing optimally. Especially in the beginning, it may be helpful to find answers to questions like "is the dosing correct?" "are there toxicities or deficiencies?"

5: Deficiencies and Toxicities

Keynotes:

• Deficiencies mean plants are lacking nutrients in some way
• Toxicity is an excess of something
• Magnesium is one of the most common deficiencies in hydroponics
• Sometimes a deficiency is a result of the growth environment 
• You can solve toxicity by replacing the water 

Deficiencies

Deficiencies occur when the plants are lacking nutrients in some way. You can have overall deficits or of a particular nutrient. When the plant is deficient, the plant starts to function and grow less and produce symptoms.

Example symptoms

• Yellowing or chlorosis shows that the plant is unable to generate enough  It could indicate a deficiency of iron or manganese, especially if your pH is high. 

• Interveinal chlorosis is the yellowing of tissue between the veins of the leaf. A potential cause can be a lack of Iron or Magnesium
• The brown edges of the leaf characterize tip burn. It can indicate a lack of calcium, drought, and some other reasons.
• Necrotic spots are black spots on the leaves as a result of tissue death. Deficiencies of nitrogen, phosphorus, potassium, and magnesium can cause these spots.
• Bronzing is when leaves turn purplish or bronze colored. It could indicate mineral imbalances.

Treating Common Deficiencies

Deficiencies happen with essential nutrient elements, i.e., nitrogen, potassium, calcium, magnesium, sulfur, phosphorus, iron, manganese, boron, zinc, copper. 

Environment and Deficiencies

Some deficiencies occur due to the environment. E.g., a lack of ventilation in humid environments can cause calcium deficiencies. So you'll need to optimize the growth environment as well as nutrients to get to incredible growth.

Toxicities

Toxicities are an excess of something. E.g., you can have metal buildup if you are using older systems for an extended period. Treating toxicities is easy. Simply replace the water with new water. 

Part 4: Making a Hydroponics system

1. Plumbing Equipment

Keynotes:

• Calculate your piping, drainage, etc. by using drawing programs
• Lights are driving photosynthesis and a crucial part of your system, especially if you're growing indoors
• Lighting, heating, and cooling require initial investment and energy costs
• Choose your pump based on your GPH requirements and the head height

Earlier, we discussed hydroponic techniques:

• NFT
• DWC
• Aeroponics
• Grow towers

In this part, we'll cover the main components of the installation.

NFT

You can get an NFT off the shelf or make one by yourselves. Buying a system off the shelf will give you the ability to check out other user reviews and see if it is easy to install, easy to clean, and most importantly, if the plants grow well. If you like to DIY, there are guidelines and videos on the internet and social media.

DWC

DWC is easy to make and inexpensive. You need to buy or build troughs and float a raft on top. 

Aeroponics

Aeroponic systems are hard to make. You would need something like a DWC tank with nozzles that spray on the roots. The system needs to operate at high pressure and low volume. You need a lot of filtration to avoid clogging the nozzles. And you need to make sure that you are not spraying the nutrients out of the plant holes. 

Growtowers

Growtowers are oriented vertically, with plants growing out of the tower. You'll pump the solution to the top, and it drips down. You need to take care of light and shadows if you're growing all around.  

2. Calculating piping, irrigation, and drainage

You need piping, pumps, sump tanks, and drippers. Use Sketchup or other drawing programs to design your hydroponic set-up. Many 3d resources are freely available on the internet. Measure the distances and estimate how much piping you need.

You can use PVC or poly tubing. Poly tubing can bend without the need for an L fitting. Use a heat gun when you need to make a sharp turn. Use enclosed tubes and avoid transparent tubes. Transparent tubes can stimulate algae growth.

3. Grow Lights

If you're growing indoors, this is one of the essential components of your system. With the right light, you'll be able to grow all-year-round, get more vigorous plants, harvest earlier, and plan better so you'll fetch higher prices. Light drives the photosynthesis process, which helps plants to grow and develop. 

You'll want the right light intensity for your crop. In general, the bigger the plant, the more light it needs. And the more plant stages you'll have (e.g., seedling, vegetative, flowering, fruiting), the more light you need. 

Lights consume electricity, so you'll need to calculate your electricity requirements. If you are using traditional lighting such as HID, it is a primary source of heat.

HortiPower lighting

We recommend HortiPower lighting since it helps your plant grow better, is energy efficient, and provides a better return on your investment than most other options. 

Calculating electrical supply

Check the wattage and input voltage of your lights. A simple formula to calculate the electricity for the day is to take the watt and multiply that by the hours and then divide by 1000 to get to kWh. For example, if the light's wattage is 20 watts and you'll operate at 10 hours per day, the result is 20watts * 10hours /1000 = 0.2 kWh. If you're planning to use solar panels or some other self-generating source, you'll also need to calculate the peak capacity that you need. E.g. 20watts * 1 hour / 1000 = 0.02 kWh peak capacity that you need. To buffer in some spare capacity, divide by power factor of, e.g., 0.95, and you'll get 0.02 / 0.95 = 0.021 kWh

In formula: Energy (kwh) = Power (Watts) * Time (Hours) / 1000

If you're getting your power from the main net, check if your main power connection can handle the ampere you'll need.

You can calculate the amps by taking the watts and dividing them by the volts. For example, you have 10 lighting fixtures with 20 watts, each with an input voltage of 220Volt. So you'll have a total wattage of 10 fixtures * 20watts  = 200 watts, divided by 220V, and you will get 0.9 which are the amps.

In formula: 

Watts = volts x amps

Amps = watts / Volts

Volts = watts / amps

You must have a sufficient power supply to power your lights; without it, you'll get flickering, or your lights won't turn on. 

Pumps

There are two types of hydroponic water pumps – inline and submersible. You can install Inline pumps outside the tank. Submersible pumps are installed directly in the water tank and transport the water within the system. Inline pumps can be powerful, and HP (horsepower) explains how powerful they are. Most growers use submersible pumps. Check the Gallons Per Hour (GPH), which is a volume metric of the pump's capacity and tells you how many gallons the pump can move in one hour. Note that GPH is not a pressure metric. It takes pressure to pump water up, so the higher you want to pump, the more pressure the water needs. Check out the "head height" information on the pump. For NFT and DWC, you don't need a huge GPH since you gently soak the system. If you're using an ebb and flow system, you'll need to calculate the capacity per minute. E.g., if you will need 100 gallons of water to flood your hydroponic system, and you'd like to finish flooding within 10 minutes, then that would be 1/6th of an hour (100 x 6 = 600 GPH) . This would equal 10 gallons per minute or 600 gallons per hour as a minimum requirement.

4. HVAC

Heating and cooling are an initial investment as well as operational energy costs. If you're growing indoors, you'll need to consider proper heating and cooling.

5. Layout Considerations

Keynotes:

• Design your system for labor efficiency first, then production. 

Design around you and your people

If you're operating a hydroponic set-up that you manage yourself, make sure the system is easy to use and easy to manage. Labor costs are one of the highest cost drivers, even in indoor farms. If you're having employees or temporary staff, you'll be paying per hour, and it is a big chunk of operational costs that come back every time.

Optimize space

Especially in urban areas, space is expensive. Try to optimize space as long as it does not decrease labor productivity.

Start small and scale as you grow

For small indoor farms, it might be wise to start small and scale as your customers require more. In this way, you can avoid large upfront investments and the need to finance them. Choose a system that is modular in design, so you'll be able to expand later on.

Part 5: Plants to Grow

Think about which crops you bring to market and which crops the market wants more. Choose crops that have stable demand and high margins. 

Plants in Hydroponics vs. Plants outdoor

In an outdoor environment, you have a lot less control over the climate. In an indoor environment with hydroponics, you can optimize the environment so that your plants will grow optimally.

Think and explore how you can induce the plants to become a more attractive product for your customers. 

Moving young plants to hydroponic systems

If you're growing plants in a seedling tray, they will receive a low EC solution regularly. Once they move to the system, they can experience some shock. Try to minimize the root damage and adjust your EC up over time. 

1: Leafy greens

Keynotes:

• Leafy greens are a great starting crop for hydroponic growers
• Leafy greens grow fast. They grow efficiently and are in high demand 
• Leafy greens need higher levels of nitrogen and lower levels of phosphorus and potassium

1. Leafy greens

Leafy greens are lettuces like crunchy romaine, smooth butterhead, kale, swiss chard, collards, and arugula. They are versatile crops, rich in flavor, and have a high nutritional value. Crops like these are often popular by consumers and chefs, and it is easy to cut-and-grow again, which means less labor on the farm.

There are three characteristics that you should know:

1. Leafy greens are a staple-vegetable crop. You can generate consistent income from these greens. 
2. Leafy greens grow fast. Most of the leafy greens grow in about 30 days from seed to harvest. They are also easy to cut and grow again.
3. Leafy greens grow efficiently. They have a small root system, and consumers can eat most of the plant matter. It means you're getting the most out of the resources you used, and you're not wasting resources on growing something that is not sellable. For example, you'll only harvest the fruit with tomatoes, but you will waste the leaves and meristem.

Lettuces are a low value and high volume crop

Lettuces are a diverse group of crops that include head lettuces and leaf lettuces. You will be able to sell large volumes, but the price can be commoditized.

Brassicas can be high in value and can be picky

Brassicas include cabbage, broccoli, cauliflower, mustard greens, and Asian. They can be pickier than lettuces.  

Watercress is easy to grow but low in demand

Watercress is an easy crop with high dollar value but low-demand.

Nutrient requirements

Leafy greens are vegetative growers, and you'll sell the leaves. So you don't want them to start fruiting. A nutrient mix for lettuces would have higher nitrogen and lower phosphorus and potassium. Be careful about the potassium or phosphorous which you need to use with a fruiting crop.

Production techniques

You can grow them everywhere. 

2. Herbs

Keynotes:

• The recommended herbs are basil and mint
• They are in demand, grow well, and can sell at a premium, where freshness enhances the consumption experience
• Basil grows fast and perishes quickly. It a high-margin crop and can get fungal infections like Downey Mildew
• Mint is cheap to produce and has market potential. The extensive root growth can damage growing systems
• Herbs accept high nitrogen levels and like a lot of potassium

Basil and mint are popular, and often they are under-served, which means there is potential to make some remarkably high margins in your local markets. People who care about quality will appreciate the oils, the alcohols, and the fantastic compounds that the leaves produce, which deliver the flavor and aroma. The flavor and aroma go away as soon as you cut the plant, making it a perfect crop to grow and sell to local restaurants, chefs, and foodies. Basil and mint enhance the experience and presentation of food and drinks. The value is in this experience and how a chef or bartender can market this to their customers. 

You can also grow herbs like sage, thyme, rosemary, but their sales volume is lower, and they take longer to grow. Start with basil and mint, and then you can consider others.

Basil 

Basil is a fragrant herb that adds freshness to any dish. There are many varieties over geographic areas, and they have their unique qualities. 

Basil grows fast and perishes quickly, which makes it a high-margin crop. Because it perishes fast, it is not suitable for long-distance transport, but it is perfect for live sales and local sales. You'll have a chance to sell superior fresh basil.

The seeds have a high germination rate of over 90%. They germinate within 5-10 days of planting. If they start to develop flowers, remove them as it affects the taste.

You might run into fungal infections such as Downey Mildew for herb crops. Nufar basil is an Asian basil variety that is less receptive to diseases, pests, and fungi. 

Mint

People want mint in their drink that looks good and is aromatic. Mint is a fantastic grower. It takes about 5-6 weeks to grow, but then you can harvest it back to the meristem. After 3-4 weeks, you can do it again. 

They grow well in NFT troughs or vertical towers. They don't grow very well in DWC. In DWC, you will have excessive root die-off and slower growth. It also has a too high oxygen demand for DWC systems.

The market potential for mint is high. Generally, bars and grocery stores will be interested. Bartenders, in general, love mint. Ask them what flavor they like. 

Nutrient Requirements

Mint takes up a lot of water and needs few nutrients. But in general, the nutrient requirements for herbs are higher than with leafy greens.

Herbs can have high nitrogen levels, and they also like potassium.

Environmental Requirements

Mint likes cooler temperatures and lower humidity. Basil also likes low humidity. The lower humidity helps to avoid fungal issues.

Production Methods

You can grow herbs typically in NFT, DWC, or vertical grow towers. 

Basil can be grown in any of these methods. Mint works well in grow towers or NFT.

3. Fruiting Crops

Keynotes:

• Fruiting crops are reproductive and therefore less efficient than vegetative crops
• Fruiting crops require pollination, and it takes relatively longer to grow
• From all fruiting crops, strawberries can be grown in NFT, vertical growth tower, and grow tents
• Fruiting crops can experience heat and drought effects
• Grow something else before you start with fruiting crops

A fruiting crop is a vegetable crop that bears fruit, which we eat. We're not eating leaves, stems, or roots of the plant. Tomatoes, bell pepper, cucumber, and eggplant are fruiting crops.

Fruiting is part of the crop's reproductive phase, and it appears after the crop has to go through germination, vegetative growth, and flowering. Most of these crops grow quite tall, except strawberries. Fruiting crops need pollination, either by hand or with bees. Most fruiting crops love light, so if you're growing them indoors, you need high-intensity light. e.g., around 300 umol/m2/s for crops like tomato and bell pepper.

Tomatoes

Tomatoes can be indeterminate or determinate. Indeterminate varieties grow and produce tomatoes during the whole growing season. With this variety, you can harvest a massive amount of tomatoes. They grow tall, and you need to support the plant. 

Determinate varieties will reach a certain height and then stop growing, and they typically stay under 5 feet/ 150 cm.

Tomatoes love lots of light and consume a lot of EC. You can even run different EC values between day and night to increase the sugar content. 

Strawberries

Strawberries are short, and that makes them more suitable for vertical farming. Get special strawberry fertilizer to optimize for the needs of this crop. They also need pollination by hand or bees. You can grow them in NFT troughs.

Nutrient Requirements

The nutrient solution is very different for vegetative crops compared to fruiting crops. When fruiting crops reach the reproduction stage, they need more potassium and phosphorus, and nitrogen becomes less critical.

You can change the EC between the vegetative and the fruit-producing stage. e.g., use higher nitrogen value to get fast growth and, once they are ready for the fruiting stage, add more potassium and phosphorus.

Environmental Requirements

These crops are extensive and take-up water from the bottom to the top of the plant. Be careful with heat and drought effects. You can consider different day and night EC values.

Production Methods

You can grow these crops on rock-wool cubes from, e.g., growdan or another substrate. Strawberries can also be done in NFT or grow towers. 

Consider other crops at first, and once you feel comfortable in growing different crops, you could start with, e.g., strawberries.

Tomatoes, Peppers, and eggplant grow in stature and weight. Hence they are not suitable for vertical farming. Should you have a grow tent, you could try with the right providing plant support.