Introduction

Hydroponics is system where plants are grown without soil and the water that has been enriched with mineral elements is provided to the plants. So instead of the plant searching for nutrients like it does in soil, the nutrients are all provided for the plant. Throughout the years scientists have discovered through extensive research that certain formulas of various elements have more control over plant nutrition, which consequently increases production. The gardener is able to provide the plants with the necessary nutrients and light source that are usually provided by Mother Nature. Some may say this is urban farming, because hydroponics can occur in any indoor facility as long as the following are controlled: light, temperature, water, CO2, oxygen, pH and nutrients. Aeroponics is a branch off of hydroponics; it is where the plant is suspended in a chamber of air and is misted with mineral enriched water in timed intervals.

The word hydroponics is comprised of two Greek words: ‘hydro’ (water) and ‘pono’ (labour). Through the use of an old method we could grow the necessary plants in a short period of time and space. Hydroponics has made appearances in the gardens of the Babylon, the Aztecs and the Chinese. It also dates back to almost 700 years before Christ in Egypt.

Background

            Hydroponically grown plants are no different than those grown in soil. The plants still need everything that a plant grown in soil needs, well except soil of course. Photosynthesis is how plants grow, there’s no other way especially in hydroponics it’s all the same good old science. When you think about hydroponics you probably think that it’s a form of unnatural form of growing freaky space plants, but indeed it is not the case.

Photosynthesis in hydroponic systems is no different from plants in soil. The carbon dioxide from the air and the water are combined to form a carbohydrate, called glucose. Light energy is used to convert the low-energy reactants, carbon dioxide and water, into a complex, high-energy product. During photosynthesis, plants convert light energy into chemical energy. Photosynthesis can be broken down into two components: the light-dependent reactions and the non-light dependent reactions. During the light-dependent reactions, light energy is converted into chemical energy and temporarily stored in ATP. The absorption of light energy also causes the loss of electrons by pigments involved in photosynthesis. The pigments replace their electrons by taking them from water molecules, and in the process, water molecules are split into two component parts: hydrogen and oxygen. The oxygen is released into the atmosphere. The hydrogen proton and its electron temporarily combine with the coenzyme NADP+. Hydroponics isn’t some weird hippy plant growing system, in fact it’s all about good science.

Soil vs. Hydroponics

If a plant grown in soil was placed next to a plant that was grown hydroponically, there would be no difference at all. In soil both the organic and inorganic components must be decomposed into inorganic elements, such as calcium, magnesium, nitrogen, potassium, phosphorus, iron and others before they are available to the plant. The elements adhere to the oil particles and are exchanged into the soil solution where they are absorbed by the plants. In hydroponics the plant roots are moistened with a nutrient solution the containing the elements they need. In the end it all means that there’s more nutrients available faster.

Nutrients

Obviously, plants need nutrition to grow and there’s no way around that fact. In hydroponics the nutrition management is fairly difficult. The principle of mass balance states that the mass of nutrients can be in two different places, in the solution or in the plant. Nutrients are placed in the water as the plants need them to grow and produce more crops. The water is removed through transpiration and consequently there is a great need to have 0.5 mM phosphorus in the refill solution. In the projection of this theory, if this refill occurred once a day the plant would absorb the phosphorous in mere hours and the phosphorous concentration in the nutrient rich solution would go down to about zero. This would be very good for the plants because it simply indicates a healthy plant with fast nutrient uptake. In the long run if the phosphorous level is kept at 0.5 mM in the refill solution it can increase the dry mass up to 1%, which is about three time more than the pinnacle of most plants. Of course all plants are different and some plants may not be able to handle that much phosphorous in an amount of time, so moderation must be considered.

            Nutrients are the food for plants, just like how we eat food to live plants need nutrients to stay alive. Just like how we have meats, vegetables and grains, plants also have food groups. The most important nutrients are grouped into three general categories of the rate of removal from nutrient rich water. The first group of elements is immediately absorbed by roots and can be taken out of the solution in a few hours. The second group of elements have mediocre uptake rates and have the ability to be remove from the solution faster than water can be removed. The third group of elements are unreceptively absorbed from the nutrient rich solution and then later build up in the solution.

TABLE 1. Approximate uptake rates of the essential plant nutrients.

One of the downfalls to hydroponics is that is requires constant monitoring. Constant monitoring must occur so the first group of elements do not build up, which is very toxic to plant tissue.

            The nutrient rich solution is very important and does need to be covered before anything else about the hydroponic system. The nutrient rich solution must have the following components: nitrogen, phosphorus, potassium, magnesium, calcium and sulfur. These components are just for plants grown hydroponically, all plants need these components to grow and bloom into wonderful plants. There are also many other nutrients that are just as important, but are not present in large amounts. The following nutrients are often found in the impurities of the atmosphere: iron, copper, manganese, boron, cobalt, molybdenum and zinc.

            The preparation of the nutrient solution is very important and should be done to the tee. There are many pre-packaged nutrient formulas that have varying success rates. Every plant is different and flourishes in different environments. Making your own nutrient rich solution isn’t complicated, but before you start you must be familiar with the proportion of ingredients and the solubility of the chemicals. One should also be aware of the possible reactions from the mixing of nutrients because when some nutrients come in contact with others unforeseen things could happen.

Calculating the Amount of Nutrient in a Chemical

            The amount of a nutrient in a compound can be calculated with the knowledge of some basic chemistry. This process is important because any unknown chemical in the solution could be harmful for the plants and that would ruin an entire crop. First and formally the chemical formula of the compound should be known. In this example we will use ammonium sulphate (NH4)2SO4. Then you must find the atomic weights of each individual element in the compound and multiply the number of atoms by the weight.

Nitrogen 2 atoms x 14 (atomic weight) = 28

Hydrogen 8 atoms x 1 (atomic weight) = 8

Sulfur 1 atom x 32 (atomic weight) = 32

Oxygen 4 atoms x 16 (atomic weight) = 64

Then add up all the weights that you calculated in the previous step to find the molecular weight.

28 + 8 + 32 + 64 = 132

Then calculate the percentage of each element in the compound.

Nitrogen 28/132 x 100 = 21.3%

Hydrogen 8/132 x 100 = 6.06%

Sulfur 32/132 x 100 = 24.24%

Oxygen 64/132 x 100 = 48.48%

Now you know the amount of nutrients in the compound and you can use this information to make up a solution. Approximately .231 grams of nitrogen would be present in one grams of the solution, so if you added one gram of the solution to 1000 liters only 0.231 grams of nitrogen is there. If you wanted exactly 1 gram of nitrogen then you would have to divide the molecular mass by the individual mass of nitrogen.

The Preparation of the Nutrient Solution

            Preparing a nutrient solution is simple, as long as the following guidelines are followed. Firstly, the nutrient chemicals must be weighed one at a time. Ensure the proportions of each chemical by dividing them into different piles. Check twice to make sure that some chemicals aren’t weighed twice. There is only a 5% error margin so be very careful. Then you must dissolve all of the nutrients into the tank, the order doesn’t matter but be sure to dissolve the less soluble salts first. Then finally check the pH and adjust it to the desired level. Now you have made a nutrient solution. Now only use this information to benefit the lives of the plants and not for evil.

Advantages

There are many advantages to growing plants hydroponically; however there are a few disadvantages. Don’t worry though; the advantages outnumber the disadvantages by tenfold.

            In a hydroponics system it’s not very hard to establish new plants and when plants are transplanted there is little to no shock. Controlling the chemistry of the roots is not a problem in hydroponics. Salt can sometimes build up in the roots and unlike other plants the salt can be sucked out of the roots. However, the chance of salt build up is slim to none because chemically salt is unable to bind to the roots in the hydroponics system, as well since there isn’t any soil there is a reduced chance of that. Hydroponics is one system where you can play Mother Nature and because of that ability you can adjust the level of pH and electro conductivity. Since you play Mother Nature, you have full control over how your plants turn out. Everything from the temperature, humidity, light and the atmosphere to the timing of nutrient delivery to the roots can be controlled by you. In the long run nutrients are conserved and don’t end up in the local water resources.

            Anybody who has gardened before knows that no matter what you grow, weeds will always pop up out of no where. However in hydroponics, weeding is none existent. Believe it or not, but the plants grown hydroponically are almost always pest and disease free. However, lots of precaution must e taken by the caretaker because many plant pests can be carried by the human body, anyone who enters into the closed hydroponic environment must be sprayed down. All that work that normally goes into gardening is all eliminated. The great thing about hydroponics is that it can be grown anywhere from a rooftop to a dirt field. The most important thing about hydroponic systems is that pesticides do not need to be used and if there is a small bug problem it can be easily fixed with organic products, which is also an advantage to using hydroponics; it’s all ORGANIC! Since it’s all organic the crops produced have a higher mineral content than the plants grown in soil.

            Of course to every good thing in the world there is an equal and opposite thing. The hydroponics system is fairly complicated and can be fairly expensive in the beginning, but in the end could be all worth all the money. Not just any normal Jane Doe can grow plants hydroponically, in fact one must have a very extensive knowledge of the hydroponics system to advance.  The hydroponics system is very sensitive and because of that disease and pest can spread rapidly. When growing hydroponically one must consider that certain plants can only be grown in soil and cannot last in a hydroponic system.

Techniques

Nutrient Film Technique

             There are many ways that hydroponics can be practiced. The most popular technique is the Nutrient Film Technique, this is the technique that I used and was shown in the video in the Background section, if you have not already seen the video please view before continuing because then you will have a better understanding of this section.

http://aquaponicslibrary.20megsfree.com/cgi-bin/i/nft-sys.jpg

            In the Nutrient Film Technique (NFT) the plants are inertly placed into long channels and a nutrient rich solution is continuously pumped through the channels to provide all the possible nutrients to the plants. The channel is often made of PVC or some other type of plastic film. On top of the channels are faceplates that provide a holder for the pot that is meshed to allow nutrients to flow into the roots. The channels are often place on a slant to allow maximum flow of water into all of the plants but the system that I used all the channels were placed flat on benches and the plants still grew at a phenomenal rate. Inside the channel it is pretty much air tight so the level of humidity is increased, which in the end helps the plant grow faster.  In NFT there are 8 basic components that it must contain.

1. Channels in which the nutrient rich solution flows trough and where the plants actually grow. There are many varieties of materials that these channels are composed of, such as: PVC, polythene (this is what is used in the system I used), concrete, corrugated PVC, fiber glass and metal.
2. A nutrient solution return pope, which discharges all of the used nutrient water.
3. A nutrient solution tank, where the nutrient rich solution is collected below the channels.
4. A pump to deliver water from the tank into the channels.
5. Sensing devices that red pH and electro conductivity.
6. Benches to place the channels on.

Rockwool Culture

            Rockwool is exactly as described in its name, it’s ground up rock that is spun into threads making a wool. It’s very light and is often sold in cubes. There is lots of space for air in between the little threads, so no matter how much water is present the plant won’t be over watered. This method is ideal because it takes longer to dry and consequently the amount of water stress is diminished. The rockwool is completely sterile and can be reused, which in the long run is very good for the plants.  Similar to the insulation in our houses, rockwool keeps the roots from getting too cold or too hot. The great thing about rockwool is that even where there isn’t a lot of water in the system the plants are still able to draw at least 10 – 20% of the water in the system. Rockwool has no effect chemical effect on the plant except for a small effect on pH. The rockwool does not take any nutrients away from the plants or the solution so the cation exchange capacity is usually at zero. The most important characteristic of rockwool is that it’s biodegradable, so it’s good for the plants and the environment.

            Rockwool is very good to use to grow plants, however in most hydroponic systems the seedlings are just merely sprouted in the rockwool and then transplanted into the NFT system. 

Aggregate Culture

http://www.ag.uiuc.edu/~vista/html_pubs/hydro/fig3.gif

            Aggregate culture is any material that has loose particles in a container. The most frequently used materials are sand, perlite and gravel. The containers that we imagine in our minds are completely different from what can actually be used in hydroponics. Anything from the floor to bags can be used as containers when growing with aggregate culture.

            The setup of the system is a little complicated, but it’s nothing that can’t be overcome. Using ausperl bags to catch the excess water, they should be arranged side by side in doubles rows. In most cases the rows of bags are raised using polystyrene so the root-zone heating pipes could be placed there. Each bag has at least three drippers that are connected to the feeder line. The bags are prepared in a special manner to provide maximum performance. First, holes should be cut into the top of the bag for the insertion of drippers. Then one or more slits are cut into the bag on the side of the drainage furrow measuring to the length of 4cm. Then perlite should be placed into the bags. Next, the nutrient rich solution should be pumped into the bag until the perlite has retained a reasonable amount of water. The last step is very simple, all that has to be done now is to simply place the plants in the perlite and voila, c’est fini!

            Now that was simple and using the system will be even easier! The perlite makes the system very easy for the user because perlite has strong capillary action it ensures that the nutrients are drawn upwards from the reservoir at the base of the bag. The great thing about the reservoir is that it is able to maintain the moisture of the roots at a desirable level.

            As soon as roots are established (usually about two weeks after the plotting of the seeds) the slits in the bags are reduced. If the water quality is good then about 10% of the solution should be drained away as waste. The electro conductivity levels should be checked regularly and if the levels exceed the desired limit then the solution should be drained out as waste during the next feed. If the electro conductivity level remains stagnant then the electro conductivity of the input solution should be reduced.

Wick Systems

            The wick system uses a fibrous material that has incredible absorption abilities and the ability to raise the nutrition using capillary action (the force of making liquid move upwards against gravity). The nutrient rich solution is provided by an aggregate bed from a tank full of the nutrient rich solution.  

Variables

            The entire process of hydroponics is based on variables that are completely controlled by the gardener. The artificial light must be on for at least 12 -14 hours a day. During the day when the lights are turned off the light isn't available for photosynthesis so it is reversed. At night, plants take in oxygen and consume the energy they have stored during the day.

The measure of pH is the measurement of positive hydrogen ions. Plants are fed by ions exchanging among each other. When ions are removed from the mineral enriched water, the pH rises. That means that the more ions that the plants have the greater the growth production will be. A solution with a pH value of 7.0 contains relatively equal concentrations of hydrogen ions and hydroxyl ions. When the pH is below 7.0, there are more hydrogen ions than hydroxyl ion. The desired pH for my system is 6 or else it will crucially affect the growth of the plant, which happened to be basil. The pH was measured with a pH tester as shown in the video and to adjust the level to the desirable level we added an acid.

When entering the hydroponics and aeroponics area, one must be sprayed of all possible bugs that could be clinging onto their clothing because it could cause a large bug problem that would ruin the entire growth process. The temperature should be kept at a constant or else the growth may not reach its maximum potential. Water plays a very important role in the photosynthesis process and we must make sure that all of the water in the system is 100% purified so that any additional elements would not get in the way of the growth process. Carbon dioxide must also be controlled in the system.

            The conductivity of the solution is very important. Conductivity is the rate that small electric current flows through a solution. In most cases where there is a higher concentration the current will flow quickly and vice versa for when there is a lower concentration. The strength of the solution is indicated by the measure of conductivity in the solution. Electro conductivity (EC) is mMho/cm and is measure at 25° C. Whenever the temperature is increased the EC is increased and when the temperature is decreased the EC is decreased. Each plant has a different optimum EC level and when the nutrient solution is used by the plant the EC drops.

            When dealing with hydroponics one must be aware of the salinity level. Plants use part of a specific nutrient from a ‘salt’ molecule provided by the nutrient solution. That means the remaining parts of the molecule stay in the hydroponic system. Sometimes the plant uses the left over parts but normally it builds up and if it reaches a certain level it could be dangerous for the plant. The build up of salinity often occurs when the media has a high cation exchange capacity or when a nutrient solution is a little past the expiration date. Salinity build up can be seen in the appearance of the plant. When there are white pipes or water outlets then there is a dangerously high level of salinity. Once the problem has been noticed, it can be treated by leaching the salt buildup by washing with water.

            Weyburn water is 340 ppm and is used in the hydroponic system, but food grade hydroxide is added to eliminate the chlorine. The following table shows all of the elements in the incoming water that was used in the hydroponic system that I used, however the composition was changed with the nutrient rich solution was added.

http://www.weyburn.ca/modules.php?name=Sections&op=viewarticle&artid=414

Aeroponics

http://aquaponicslibrary.20megsfree.com/aeroponics.jpg

            Aeroponics is a branch off of hydroponics. It is a similar technique to hydroponics but instead of the roots being suspended in water the plant is misted with a nutrient rich solution in set period intervals. Through an experiment I conducted earlier this year I have discovered that under the same enclosed environment the aeroponics system produces more crops over a period of time than hydroponics (if you would like to read about the experiment I conducted earlier this year click here). In fact the growth rate is 50% higher than that in hydroponics. The growth rate is so incredible because the nutrient rich solution is saturated with oxygen so all the water is broken down into smaller particles. This is done by constantly circulating the water through the system. This is similar to a tropical rain forest.  The study of aeroponics has led to many innovations in the following fields: root morphology, water stress and nutrient uptake.

Advantages of Aeroponics

• Aeroponically grown plants developed a very high number of small nodules distributed all along the root system, resulting in an increase in nitrogen and chlorophyll content in plant tissues.
• Can be grown anywhere that soil cannot be used.
• Can grow at an amazing rate
• The fast growth rate means cutting out cost of transporting produce
• Constant care of soil is unnecessary (tilling, cultivation)