Hydroponic gardening is easy and fun once the concept and principles are understood. There are a few basic rules that must be followed to make a good hydroponic system productive. First, let's look at how and why hydroponics works. In the basic hydroponic system, the inert soilless medium contains essentially no nutrients of its own. All the nutrients are supplied by the nutrient (fertilizer) solution. This solution passes over the roots or floods around them at regular intervals, later draining off. The extra oxygen around the roots is able to speed the plants' uptake of nutrients. Plants grow faster hydroponically because they are able to assimilate nutrients faster. They are able to take in food as fast as they are able to utilize it. In soil, as in hydroponics, the roots absorb nutrients and water; even the best soil rarely contains as much oxygen as a soilless hydroponic medium.

Hydroponics works well for horticulturists who are willing to spend a few extra minutes a day in their garden. The garden requires extra maintenance. Plants grow faster and there are more things to check. In fact, some people do not like hydroponic gardening because plants grow too fast and require additional care.

Hydroponic gardening can become overwhelming for the novice gardener if too complex of a system is implemented at first if you are a novice gardener and want to garden hydroponically, try setting up a basic system. Once you have gained experience and feel comfortable with hydroponics, move to a more elaborate system. Remember, if you buy all the new little hydroponic garden gadgets available, you may start more projects than you can manage effectively. If you are contemplating constructing and inventing your own unit, get your hands wet with a tried and true system first it will take a month or two to work out most of the bugs in a homemade unit.

Hydroponic gardening is exacting and not as forgiving as soil gardening. The soil works as a buffer for nutrients and holds them longer than the inert medium of hydroponics. Some very advanced hydroponic systems do not even use a soilless mix. The roots are suspended in the air and misted with nutrient solution. The misting chamber is kept dark so algae does not compete with roots. This form of hydroponics is called aeroponics.

Plants properly maintained, grown hydroponically under HID lamps tend to grow more lush foliage and at a faster rate than plants grown in soil. The real benefit with hydroponics is realized later in the plant's life. When roots are restricted and growth slows in containerized plants, hydroponically grown plants are still getting the maximum amount of nutrients.
 

The above is an excerpt from George Van Patten's book, "New Revised Gardening Indoors".

What is pH, and how can I test for it?
pH stands for "Potential of Hydrogen" and is the symbol for the hydrogen ion (H+) in liquids. pH has a range from 0 (acidic) - 14 (alkaline), with 7 being neutral. For hydroponics we are aiming for a pH between 5.5 to 6.2 (slightly acidic); this is suitable for most hydroponic crops. For soil, we want the pH a little higher but still slightly acidic; around 6.0 to 6.5. Ensuring that the pH remains within this range will help maintain good plant health. Keeping the pH in this range ensures that nutrients are readily available to the plant. Once the grower goes above or below this optimal range certain nutrients start becoming unavailable to the plant (e.g. iron deficiencies will appear at a pH of 6.5 and above).

All hydroponic growers need to test the pH of their nutrient solution for successful growing. The pH of a solution can be tested using a standard pH test kit (sample vial with drops of indicator solution), litmus test strips, or a digital pH meter. Litmus paper and standard test kits are cheap and easy to use; however, the degree of accuracy isn't very high. Digital pH meters, although more expensive than the alternatives, are easy to use and very accurate.





Should I top-off my reservoir with plain water or nutrient solution?
In the summer or in hot grow rooms, plants, in general, will take up more water than nutrients, thus causing the nutrient solution to become more salty. In the winter time or in cooler grow rooms, the opposite will occur. Nutrient uptake will also be determined by the type of crop being grown e.g., tomatoes are heavier feeders than lettuce. It is extremely important that the grower has both a TDS meter and a pH meter and that regular testing on the nutrient solution is carried out. If the grower notices after a few days that the ppm level in the reservoir is high and the water level has decreased than the grower should top up their reservoir with either plain water or a weak nutrient solution until the optimum ppm level is reached. If the grower has noticed a drop in ppm levels then a full strength nutrient solution should be used to top off the reservoir. Another factor to consider is the source water. You will generally find that if you are not using reverse osmosis water, you will usually have to top-off with plain water, since tap water has a lot of sodium and minerals that increase the ppm levels.





Common nutrient disorders in hydroponic systems

Nutrient Disorders
Nutrient disorders are caused by too much or too little of one or several nutrients being available. These nutrients are made available between a pH range of 5 and 7 and a total dissolved solids (TDS) range of 800 to 3000 PPM. Maintaining these conditions is the key to proper nutrient uptake.

Nutrients
Over twenty elements are needed for a plant to grow. Carbon, hydrogen and oxygen are absorbed from the air and water. The rest of the elements, called mineral nutrients, are dissolved in the nutrient solution. The primary or macro-nutrients (nitrogen (N), phosphorus (P) and potassium (K)) are the elements plants use the most. Calcium (Ca) and magnesium (Mg) are secondary nutrients and used in smaller amounts. Iron (Fe), sulfur (S), manganese (Mn), boron (B), molybdenum (Mo), zinc (Zn) and copper (Cu) are micro-nutrients or trace elements. Trace elements are found in most soils. Rockwool (hydroponic) fertilizers must contain these trace elements, as they do not normally exist in sufficient quantities in rockwool or water. Other elements also play a part in plant growth. Aluminum, chlorine, cobalt, iodine, selenium, silicon, sodium and vanadium are not normally included in nutrient mixes. They are required in very minute amounts that are usually present as impurities in the water supply or mixed along with other nutrients. The above nutrients are mixed together to form a complete plant fertilizer. The mix contains all the nutrients in the proper ratios to give plants all they need for lush, rapid growth. The fertilizer is dissolved in water to make a nutrient solution. Water transports these soluble nutrients into contact with the plant roots. In the presence of oxygen and water, the nutrients are absorbed through the root hairs.
 

*NOTE: The nutrients must be soluble (able to be dissolved in water) and go into solution.

Nitrogen
(N) is primary to plant growth. Plants convert nitrogen to make proteins essential to new cell growth. Nitrogen is mainly responsible for leaf and stem growth as well as overall size and vigor. Nitrogen moves easily to active young buds, shoots and leaves and slower to older leaves. Deficiency signs show first in older leaves. They turn a pale yellow and may die. New growth becomes weak and spindly. An abundance of nitrogen will cause soft, weak growth and even delay flower and fruit production if it is allowed to accumulate.

Phosphorus
(P) is necessary for photosynthesis and works as a catalyst for energy transfer within the plant. Phosphorus helps build strong roots and is vital for flower and seed production. Highest levels of phosphorus are used during germination, seedling growth and flowering. Deficiencies will show in older leaves first. Leaves turn deep green on a uniformly smaller, stunted plant. Leaves show brown or purple spots. NOTE: Phosphorus flocculates when concentrated and combined with calcium.

Potassium
(K) activates the manufacture and movement of sugars and starches, as well as growth by cell division. Potassium increases chlorophyll in foliage and helps regulate stomata openings so plants make better use of light and air. Potassium encourages strong root growth, water uptake and triggers enzymes that fight disease. Potassium is necessary during all stages of growth. It is especially important in the development of fruit. Deficiency signs of potassium are: plants are the tallest and appear healthy. Older leaves mottle and yellow between veins, followed by whole leaves that turn dark yellow and die. Flower and fruit drop are common problems associated with potassium deficiency. Potassium is usually locked out by high salinity.

Magnesium
(Mg) is found as a central atom in the chlorophyll molecule and is essential to the absorption of light energy. Magnesium aids in the utilization of nutrients, neutralizes acids and toxic compounds produced by the plant. Deficiency signs of magnesium are: Older leaves yellow from the center outward, while veins remain green on deficient plants. Leaf tips and edges may discolor and curl upward. Growing tips turn lime green if the deficiency progresses to the top of the plant.

Calcium
(Ca) is fundamental to cell manufacture and growth. Soil gardeners use dolomite lime, which contains calcium and magnesium, to keep the soil sweet or buffered. Rockwool gardeners use calcium to buffer excess nutrients. Calcium moves slowly within the plant and tends to concentrate in roots and older growth. Consequently young growth shows deficiency signs first. Deficient leaf tips, edges and new growth will turn brown and die back. If too much calcium is applied early in life, it will stunt growth as well. It will also flocculate when a concentrated form is combined with potassium.

Sulphur
(S) is a component of plant proteins and plays a role in root growth and chlorophyll supply. Distributed relatively evenly with largest amounts in leaves which affects the flavor and odor in many plants. Sulphur, like calcium, moves little within plant tissue and the first signs of a deficiency are pale young leaves. Growth is slow but leaves tend to get brittle and stay narrower than normal.

Iron
(Fe) is a key catalyst in chlorophyll production and is used in photosynthesis. A lack of iron turns leaves pale yellow or white while the veins remain green. Iron is difficult for plants to absorb and moves slowly within the plant. Always use chelated (immediately available to the plant) iron in nutrient mixes.

Manganese
(Mg) works with plant enzymes to reduce nitrates before producing proteins. A lack of manganese turns young leaves a mottled yellow or brown.

Zinc
(Z) is a catalyst and must be present in minute amounts for plant growth. A lack of zinc results in stunting, yellowing and curling of small leaves. An excess of zinc is uncommon but very toxic and causes wilting or death.

Copper
(C) is a catalyst for several enzymes. A shortage of copper makes new growth wilt and causes irregular growth. Excesses of copper causes sudden death. Copper is also used as a fungicide and wards off insects and diseases because of this property.

Boron
(B) is necessary for cells to divide and protein formation. It also plays an active role in pollination and seed production.

Molybdenum
(Mo) helps form proteins and aids the plant's ability to fix nitrogen from the air. A deficiency causes leaves to turn pale and fringes to appear scorched. Irregular leaf growth may also result.
 

The above text is an excerpt from George Van Patten's excellent book "Gardening Indoors with Rockwool"

pH and PPM values for different plants (hydroponic gardening only)
A few facts about PPM, TDS, EC, cF, and pH
1. Electro-Conductivity (EC) or Conductivity Factor (cF) can be expressed as either milliSiemens (mS), cF, or parts per million (PPM) 1 mS = 10cF = 700ppm.

2. The pH and electro-conductivity values specified here are given as a broad range. It should be noted that specific plant requirements will vary according to regional climatic conditions, and from season to season within that region.

3. As a general rule, plants will have a higher nutrient requirement during cooler months, and a lower requirement In the hottest months. Therefore, a stronger nutrient solution should be maintained during winter, With a weaker solution during summer when plants take up and transpire more water than nutrients.

4. KNOW YOUR CROP. Plant EC or cF may vary according to the stage of growth. For example, cucumber prefer 20cF when establishing, and 25cF after the first harvest. Between 5 and 7 weeks after first harvest, the optimum cF is 17.

5. The nutrient solution should be discarded at regular intervals. Should there be a requirement to flush the growing bed, the system should be flushed with fresh nutrients (run-to-waste) rather than water to avoid starving or stressing plant.

The following are links to charts for pH / PPM / EC for different plants grown in hydroponics.
 

End of each crop