Foothill Hydroponics Inc. Frequently Asked Questions for Hydroponic Gardeners.

We have run across many interesting questions since the store was founded in 1961. We have compiled a reference guide with the answers to the most common Frequently Asked Questions (FAQ's) as a service for teachers, students and home hobby gardeners. We hope that it will be helpful to you!

Subject Categories:

1.   Nutrients (Macro and Micro, including how water quality and pH affects nutrients)

2.   Irrigation (How plants are given nutrients, drip, ebb & flow, 3.   Air (How do temperature and humidity affect plants, and using CO2 enrichment)

4.   Light (What light color, intensity and photoperiod have to do with plant growth)

5.   Propagation (How to start seedlings and cuttings hydroponically)

6.   Insects (How to deal with insect pests in the most effective ways)

7.   Disease (How to keep bad fungi and bacteria from infecting your plants)

Before we begin discussing Hydroponics let us first examine what makes a plant grow (the basic biological process that is the same in soil or in Hydroponics) by asking the question: How do plants grow?

Plants grow by means of 4 different processes:

1.   Photosynthesis

2.   Respiration

3.Transpiration

4.Absorption

The word "photosynthesis" comes from the Greek "photo" (light) and "synthesis" (putting together). Molecules of water and carbon dioxide react with chlorophyll and light in the plant leaves. The result is the formation of a simple sugar made of 6 parts carbon, 12 parts hydrogen and 6 parts oxygen. This sugar is then used to make other materials using

enzyme  and proteins. One corn plant can produce 5 grams of sugar during a 14-hour summer day!

Photosynthesis is the process of making sugar from the following:

I.    Light

2.     Chlorophyll

3.     Carbon dioxide

4.     Water

Respiration is a more complex process that is somewhat the reverse of photosynthesis, in that sugar is consumed as the energy source to fuel the making of complex proteins and oils, the movement of water and mineral nutrients to the leaves (making those nutrients into actual cells or plant tissue), and the movement of plant foods to where they are needed for growth. Please note the following relationships between photosynthesis and respiration. A green plant in the dark loses weight as stored sugar is respired, and no photosynthesis occurs. Sugar is made only during photosynthesis, and is used up in respiration. The amount of sugar made must be more than that used in respiration or no growth can occur. Respiration happens constantly in every cell night and day!

Transpiration is described as the loss of water by evaporation through the stomata (pores) in the leaves. About 95% of all water drawn up by the plant is lost by transpiration. The remaining 5% is used in photosynthesis, and for cell growth and moisture. Water vapor low in _CO2 evaporates and is replaced by dry air with higher _CO2 content. This is how plants obtain the _CO2, they need for photosynthesis. This transpiration is what drives the last process called absorption.

Absorption is how plants take in water and mineral nutrients, along with oxygen and _CO2. Most absorption happens in the roots. The force behind it is osmosis, which is the ability of a semi-permeable membrane to let water with less dissolved nutrients pass through to the side where the mineral concentration is higher. The concentration of nutrient must be higher in the sap of the plant than that of the hydroponic solution (or soil water) or the plant cannot absorb water! Oxygen must be available to the roots or else they will actually suffocate and die.

Nutrients_________________________

What are "Macro Elements" ?

Macro elements are those used in large quantities by plants. There are nine of them:

Nitrogen, phosphorous, potassium, carbon, hydrogen, oxygen, calcium, magnesium and sulphur. The air and water provide carbon, hydrogen and oxygen. All other elements must be taken in as dissolved nutrient salts in solution. These are the main ingredients of a Hydroponic nutrient formula.

What are "Micro Elements" ?

Micro elements are vital to healthy plant growth, but are needed only in very minute amounts. They number seven: Iron, manganese, copper, zinc, chlorine, boron and molybdenum. They may be needed in amounts of less than I Part Per Million (PPM), but plants will not complete a healthy growth cycle without them. Many of them may he toxic to the plant at only a few PPM. This is why a balanced Hydroponic nutrient formula is mandatory for successful fruiting.

Do plants use any other elements?

Yes. Most plants will draw up and make use of other elements. The element silicon is accumulated in the tissue of many plants. It causes a stronger cell wall that is more resistant to fungal attack and wilting. Other elements that plants will uptake include nickel, aluminum, lithium, vanadium, cobalt, selenium, arsenic and lead. Many plants will draw up amounts of these elements that could be harmful or toxic to humans and livestock. That is why high-purity nutrients are required for Hydroponic food gardens.

What do the numbers on the fertilizer label mean when it says "15-10-30" ?

Those numbers represent the amounts of nitrogen, phosphorous, and potassium that are in the nutrient, and are always listed in that order, according to California state agricultural regulations. The other elements will be listed on the label, and the chemicals used to make the formula must be specified as well.

What is the difference between a "Vegetative" formula and a "Bloom" Hydroponic nutrient formula?

The main difference is that growth or vegetative formulas have a very high percentage of nitrogen in relation to phosphorous. A typical growth formula will be something like 20-10-20, or 15-10-13, for example. A typical   flowering formula would be something like 6-3-30, or 3-38-38.  The bloom formulas usually have a higher percentage of both phosphorous and potassium than that of nitrogen.

When would a "Bloom" formula be used?

The best time to switch to a bloom formula is after your plants just start flowering, for most crops. Switching for vine crops may be done as soon as the plants reach the desired height. The lower nitrogen will slow excessive vine growth and encourage heavy flowering. The third use of a bloom formula is for small seedlings and cuttings. The lower nitrogen and higher phosphate stimulate more root growth and sturdy stalks. Use the bloom formula at half strength for the little plants.

What is iron chelate?

This is a form of iron that is bound to another chemical that makes it available to plants over a wide pH range. The most common one in Hydroponic nutrient formulas is known as "EDTA," which produces a form of soluble iron that is very resistant to oxidation by peroxide or ozone treatments. This form of iron is also very resistant to forming insoluble precipitates, over a wide pH range. In soil, humic acids perform a similar function. Other elements may be chelated also.

Why do liquid Hydroponic nutrient concentrates have two-or three-part formulas?

The reason is that at the high strength of the concentrates, calcium and phosphorous, or calcium and sulfur will combine to form insoluble precipitates. Iron and phosphorous will combine to form insoluble iron

How is nutrient strength measured?

The measurement tool used is a conductivity meter. It measures the flow of current between two electrodes set a fixed distance apart. The more chemical salts there are in the water the more conductive it becomes, which translates into a higher reading on the meter. The standard in the U S. is called PPM or Parts Per Million. The problem is that all nutrient salts do not ionize to the same degree. To compensate for that fact, most Total Dissolved Salt (TDS) meters use a correction factor of 0.7, or in other words they multiply the reading by 0.7 to obtain a reading that simulates the average ionization of most fertilizers.

Why do some books recommend a nutrient strength speci­fied in "ECw" or "mMho"?

These terms are often used by European, Canadian and Australian gardeners. ECw stands for Electrical Conductivity of water. The term mMho stands for milliMhos which is the conductance of water between electrodes placed I centimeter apart. The conversion factor to relate ECw to Parts Per Million is: (ECw) x (0.7) x (I 00) TDS (in PPM).

Will my TDS meter tell me when to add nitrogen or potassium?

No, the TDS (ECw) reading is the total of all nutrients. It will not tell how much of any one element is in solution.

How can I test my Hydroponic solution for individual elements?

This could be done using ion-specific meters, which are very expensive and prone to contamination by other elements in the solution. There are also some possible chemical tests, but since the costs of the nutrient is so low it is generally not worth the expense of testing the solution for hobby or educational growers.

Is Hydroponic produce considered "organic" produce?

The most commonly used Hydroponic nutrient formulas are not allowed as fertilizers according to most state organic produce certification programs. Rockwool is allowed as a growing substrate in certified organic production. Most Hydroponic crops are pesticide free, as control of sanitation and fast crop growth reduce the need for pesticides. True

organically derived nutrient formulas are available, but are expensive, and require more skill in application to get good consistent crop yields.

Can plants be grown in an "organic Hydroponic" system?

Yes plants can be grown hydroponically without using the purified nutrient chemical salts found in standard Hydroponic mixes. The organic mixes usually depend upon bacterial action to reduce the organic matter into a soluble form. Compost tea and manure tea are forms of a naturally derived Hydroponic nutrient solution. The problem is knowing what the exact mineral content of the solution is at any given point. Non-ionic chemicals like urea and sugar found in manure will not register on a TDS (conductivity) meter.

Are there organic supplements to complement typical Hydroponic nutrient formulas?

There are several          n organⁱc addⁱtⁱves that help stimulate growth. Humic
 acid extracts are one class of additives that help stabilize pH and stimulate nutrient absorption. Kelp (seaweed) extracts also are very helpful. They contain a type of growth hormone called "cytokinins" that stimulate cell division and growth. The class of plant hormones known as "auxins" are also used to stimulate root growth of cuttings and transplants. Auxins also promote growth at the very tip of a growing plant shoot. Most auxins available made in the laboratory.

Nutrients and the effects of pH on the nts and the effects of pH on the nutrient solution    

What does the term "pH' mean?

The term pH is scientific shorthand for the words "potential Hydro­gen" and is always spelled with a small "p" and uppercase "H". It is a measure of the acidic or basic (alkaline) value of a solution. The pH scale goes from 0 to 14. The exact neutral point is 7, and all values lower are acidic. All values higher than 7 are basic, also sometimes referred to as alkaline in older text books. Alkalinity is a condition caused by dissolved carbonates and bicarbonates which tends to buffer a solution back to above 7, even after large amounts of acid are added.