| Intro | Light | Nutrients | Propagation | Systems |
NUTRIENT SOLUTIONS
Nutrient
solutions
Carbon dioxide
Carbon dioxide supplementation
Oxygen
Water temperature
Water
Water quality
pH regulation
Essential elements
Beneficial elements
Liquid seaweed
Commercial nutrient formulas
A and B mixtures
Grow and bloom formulas
Custom nutrient formulas
Nutrient deficiency and toxicity
Plant tissue analysis
Nitrogen
Phosphorous
Potassium
Calcium
Magnesium
Sulfer
Electrical conductivity
Summary
Hydroponic gardening is the way of the future for environmentally
controlled agriculture. By carefully controlling nutrient
levels, light and temperature, phenomenal yields can be
achieved in a relatively small space.
NUTRIENT
SOLUTIONS
Precise nutrient control is a major advantage with hydroponics
over soil based growing. Some soils have nutrient deficiencies,
but once fertilizer salts are added, there is no easy way
to change or reduce their concentrations. Hydroponics, on
the other hand, makes nutrient manipulation easy.
Specially prepared nutrient formulas can be added directly to the hydroponic solution, providing the ideal nutrient balance for various stages of a plant's life. When all of a plant's nutritional and environmental needs are met, the plant will flourish and yields will increase.
Before we look at specific nutrient formulas, lets review some of the plant's basic nutritional needs.
CARBON
DIOXIDE
Nearly 50% of a plant's dry weight is carbon, most of which
comes from carbon dioxide in the atmosphere. Carbon dioxide
enters the plant through stomata, or pores, on the leaves.
In a process called photosynthesis, the plant combines carbon
dioxide and water, using light energy as its power source,
to produce simple sugars. Excess water and oxygen are released
back into the atmosphere as byproducts of photosynthesis,
and most of the sugars are stored in the roots, stems and
fruit of the plant for later use.
Carbon
Dioxide Supplementation
Carbon dioxide supplementation can be useful in some applications.
If all of the other environmental factors are at optimum
levels, such as light intensity, nutrient levels, temperature
and humidity, increased CO2 can provide the extra material
necessary to help the plant to flourish.
C O2 Tanks
Carbon dioxide can be supplemented in different ways. On
a small scale, CO2 tanks can be used. Flow meters can precisely
control the amount of extra carbon dioxide being released
into the grow room, and timers can be used to stop the flow
at night, when CO2 is no longer of significant use. For
a 10' X 10' grow room, a flow rate of about 1 cubic foot
per hour should yield excellent results.
C O2 Generators
For larger growrooms and greenhouses, CO2 generators can
be used. CO2 generators burn natural gas or propane, producing
carbon dioxide as a byproduct. Smaller units are available
for 300-600 square foot rooms, and larger units offer saturation
capacity up to 3600 square feet.
OXYGEN
Oxygen is the fuel the plant uses to produce plant tissues.
Free oxygen (O2) is taken in through the plant roots as
part of the respiration process. During respiration, oxygen
is combined with stored glucose to release energy. The energy
is used to fuel a series of complex chemical reactions necessary
for the life and growth of the plant. Carbon dioxide and
water vapor are released back into the atmosphere as byproducts
of respiration.
Rockwool
Adequate aeration of the roots is very important in any
hydroponic system. Rockwool has high oxygen and water retention
capabilities. If adequate drainage is provided, it is nearly
impossible to over water and kill the plant, since it is
lack of oxygen, not excess water, that usually causes the
most harm.
Aeroponics
Aeroponics, a system in which the plant roots are suspended in air, provides the best aeration of all. A highly oxygenated mist chamber provides an ideal environment for root growth. The mist chamber provides plenty of free oxygen for use by the plants, while providing a perfect environment to disperse excess carbon dioxide. Strong, healthy root growth results in fast-growing, healthy plants!
Water
Temperature
Water temperature is also important for element intake.
If the water is too cold, nutrient uptake will be restricted
and growth will be slowed. If the water temperature is too
hot, the water cannot retain enough dissolved oxygen, and
plant growth will be restricted. Submersible heaters can
help regulate root temperature and improve the availability
of oxygen and other nutrients to the plant.
The importance of water to plant growth is obvious to the most casual observer; without water there can be no life. Water provides the plant with the hydrogen needed for producing essential carbohydrates (sugars), as well as providing the internal transportation medium for the entire plant. Water is taken up by the roots, carrying nutrients throughout the plant in the form of tiny charged particles called ions, and transpired from the leaves as water vapor. The transpiration of water from the leaves cools the plant and helps pull more water up from the roots.
Water Quality
Water quality is very important in hydroponics. Ideally,
distilled water should be used as a hydroponic base, but
obtaining adequate quantities of such water is usually impractical
or economically unfeasible. If well water or city water
is used, a water analysis should be performed by your local
municipal water company or by a private lab. If city water
is used, sodium chloride levels should not exceed 50 parts
per million. Filtering systems, such as reverse osmosis
systems, can significantly improve the quality of either
city or well water.
If "hard water" is used, make sure that bicarbonate levels (HCO3-) don't get too high. As bicarbonate levels increase, so does pH. pH (potential hydrogen) is the measure of the acidity or alkalinity of a solution. If pH is too high, certain elements, such as iron, become unavailable to the plant. Phosphoric acid can be used to reduce the pH of hard water, but too much phosphorous can also be detrimental to plants, hindering the availability of other essential elements, such as zinc. Nitric acid can be used as a substitute for phosphoric acid, but it is more hazardous to handle.
pH
REGULATION
The pH levels of the solution should be monitored daily
to insure optimal utilization by the plant. pH is the acidity
or alkalinity of the nutrient solution. A pH of 7 is neutral,
under 7 is acidic and over 7 is alkaline. The ideal pH level
for absorbing nutrients by the plant roots is between 5.8
and 6.4, or slightly acidic.
pH can be measured by using water test kits. The solution is placed in the holder and the test chemical is added. By comparing the colors in the windows, an accurate reading can be made.
If the pH is too high, (shown here
by the blue color), adding a solution with nitric or phosphoric
acid will lower it. If the pH is too low, (shown here by
the reddish color) a solution with potassium hydroxide will
raise it. For most plants, a pH balance of 6.0 is an ideal
target.
ESSENTIAL ELEMENTS
Plants require 16 essential elements to grow and reproduce. As we have just seen,
Oxygen,
Carbon, and
Hydrogen
come from water and air and are essential to photosynthesis and respiration. These elements account for more than 95% of a plant's dry weight.
The other 13 essential elements are
minerals, and are provided in the hydroponic solution.
Macroelements
Macroelements, those elements used in greatest quantity,
include:
Nitrogen, a critical component of vegetative growth.
Phosphorus,
and Potassium, especially important during flower and fruit
production.
Calcium, for strengthening the stems and shoot system.
Magnesium, the central element of chlorophyll, essential for photosynthesis.
Sulfur, present in some amino acids
and vitamins.
Microelements
Microelements, or trace elements include:
Iron, a chlorophyll activator important to photosynthesis.
Manganese, an enzyme activator used in chlorophyll synthesis.
Boron, essential for the transport of photosynthates, especially important during flowering and fruiting.
Zinc, part of certain enzymes and growth regulators.
Copper, part of certain enzymes and chlorophyll synthesizers.
Molybdenum, present in certain enzymes needed for nitrogen reduction.
Chlorine, a photosynthesis stimulator,
also needed for root and shoot growth.
Though used in smaller quantities, microelements are still
"essential elements" needed for photosynthesis
and growth; without them the plant will die.
Although not "essential"
for growth and reproduction, some elements are beneficial
for the health and growth of plants. Some of these "beneficial
elements" include:
Arsenic (As)
Cobalt (Co)
Chromium (Cr)
Fluorine (F)
Iodine (I)
Nickel (Ni)
Selenium (Se)
Silicon (Si)
and Vanadium (V).
For example, recent studies with greenhouse grown tomatoes and cucumbers have shown that with adequate silicon, plants are more vigorous and unusually resistant to fungus disease attack. Best growth is obtained when the nutrient solution contains potassium silicate or 10 parts per million of silicic acid (H2SiO3).
Liquid
Seaweed
Liquid Seaweed provides many beneficial trace elements.
It can be added to the nutrient solution, or it can be applied
as a foliar spray for absorption of trace elements directly
through the leaves.
Seaweed solution contains micronutrients and enzymes immediately available to plants. When used just before flowering, the flower's color and bouquet will be enhanced and the flavor of fruits and vegetables will be improved.
Commercial nutrient formulas provide all of the essential elements needed for general hydroponic growing.
A
and B Mixtures
Most commercial nutrient solutions come in A and B mixtures.
The A mixture is measured and added to the water first.
The reservoir is then filled almost to full and the B mixture
is added. A and B mixtures are kept separate in their concentrated
forms to prevent chemical reactions that could decrease
the effectiveness of some nutrients.
For example, in concentrated form, calcium and phosphorus may join together to form calcium phosphate, which plants are unable to use. Phosphorus can also combine with magnesium to form magnesium phosphate, another unusable compound. Once diluted in water, however, calcium, phosphorous and magnesium maintain their balance and remain available to the plant.
Grow and Bloom Formulas
Commercial "Grow" and "Bloom" nutrient solutions are available. Research shows that a plant requires more nitrogen at the beginning of its growth cycle, so a nitrogen-rich "grow" formula is used. Grow formulas contain increased levels of potassium nitrate, calcium nitrate and magnesium sulfate, giving the plant a nutrient boost for vigorous growth, without becoming toxic to the plant.
Once flowers appear, the plant generally requires more phosphorus and potassium. So the "grow" formula is flushed from the medium, and the "bloom" formula is added. Grow formulas have 2 times the monopotassium phosphate of grow formulas, with additional compounds added such as potassium sulfate. By regulating grow and bloom nutrients, more of the plants energy can be put into fruit production at the appropriate time.
CUSTOM
NUTRIENT FORMULAS
Custom nutrient formulas can be mixed to provide even more
precise control over the growth cycle.
Not all plants use nutrients equally during each growth stage. For example, a lettuce grower would not use a "bloom" formula, since fruiting and flowering need not be promoted. Nutrient solutions for tomatoes contain potassium sulphate in both the "grow" and "bloom" formulas, providing almost twice the sulfur content that formulas for lettuce or cucumbers do. Cucumbers use nearly twice the calcium nitrate that tomatoes or lettuce use during the vegetative growth stage, but the same amount that tomatoes use during the fruiting and flowering stage.
Even finer nutrient adjustments can be made to take into account such factors as lighting, temperature and humidity at various stages of the plant's growth, providing even better yields.
Although custom formulas offer many potential benefits when mixed properly, many potential problems may arise if mixed improperly.
NUTRIENT
DEFICIENCY AND TOXICITY
If fertilizer salts are not mixed in the proper proportions,
nutrient deficiencies or toxicities may result, harming
the plant. Generally speaking, however, it is best to err
on the side of too little of an element than too much. Deficiencies
can usually be corrected quite easily, but toxicity can
permanently damage an entire crop.
Plant
Tissue Analysis
The most accurate way to determine if plants are getting
the right amount of nutrients is through a plant tissue
analysis.
Small home test kits can be purchased to test for some macroelements and microelements. A tissue sample is collected and the sap is combined with a reagent chemical. A color comparison chart indicates the relative intensities of certain elements. Although home kits can provide a good approximation of macroelements and microelements, for a full analysis of macro and trace elements, the tissue must be sent away to a well equipped lab.
Some nutrient imbalances can be recognized and corrected without a tissue analysis. To better recognize some typical symptoms of nutrient imbalances, lets take a closer look at the role of the 6 macroelements:
NITROGEN
Nitrogen has an important role in plant growth and plant
yield, and it is absorbed most readily by the plant in the
form of nitrates (NO3). Too much nitrogen can be detrimental
to the plant, producing lush-looking plants but with few
blossoms and poor fruit set. Nitrogen is a mobile element.
Therefore, if a deficiency occurs, nitrogen will be leached
from the lower leaves first, with the appearance of the
following symptoms:
Foliage becomes yellow (chlorotic).
"Firing" (browning) appears on the tips and margins of leaves.
Vegetative growth is slowed, resulting
in stunted plants.
PHOSPHOROUS
Phosphorous stimulates early growth and root formation, and it is absorbed by plants as phosphates (PO4). Phosphorous also hastens the maturation process and promotes seed production. Phosphorous is a mobile element and is greatly affected by temperature. Cold temperatures will hinder phosphorous uptake by the plant.
Too much phosphorous will hinder the normal functions of other elements such as iron, manganese and zinc, resulting in yellowing between the veins of newer leaves, with the leaves eventually dying and dropping off.
Phosphorous deficiency produces the following symptoms:
Slow growth with thin stems and small leaves.
Purplish coloration of foliage on some plants.
Dark green coloring with the tips of the leaves dying.
Delayed maturity with poor fruit production.
Potassium is taken up by the plant in the form of potassium ions (K+). High potassium levels are necessary for protein synthesis and fruit production, but too much potassium can induce a calcium or magnesium deficiency.
Potassium is also a mobile element, with the following deficiency symptoms first appearing in the lower leaves:
Older leaves develop marginal burning.
Weak stalks.
Slow growth.
Forward curling of leaves.
CALCIUM
Calcium is absorbed by plants as a calcium ion (Ca++), and
it is essential for the formation and structure of cells.
Calcium is a non-mobile element, so signs of deficiency
occur first in the newer leaves:
Shoot tips yellow and die back.
Abnormal dark green foliage.
New leaves distorted.
Premature shedding of blossoms and buds.
Root tips die and acquire black spots.
Magnesium is used by plants in the form of a magnesium ion (Mg++), and is the central element in chlorophyll, essential for photosynthesis and other growth processes.
Magnesium deficiency symptoms include:
Yellowing of older leaves.
Withering of leaves.
Upward curling of leaves along margins.
SULFUR
Sulfur is absorbed by plants as SO4, and it is a chief component
of amino acids, essential for protein synthesis. It also
strongly effects a plant's bouquet. Sulfur is a non-mobile
element. Symptoms of sulfur deficiency are similar to nitrogen
deficiency, except the symptoms appear first in the upper
leaves:
New leaves appear light green to yellowish.
Small spindly plants.
Retarded growth and delayed maturity.
ELECTRICAL CONDUCTIVITY
The EC, or electrical conductivity, of the solution is also
important for plant growth. Distilled water has an EC of
about zero; it doesn't conduct electricity. The higher the
concentration of minerals in the water, the higher the conductivity.
A conductivity meter can be used to test EC. An EC range of 1.5-3.5 Mhos is generally desirable. A low EC reading means a slightly dilute concentration. Lower to middle levels of EC promote plant growth, and should be used in the rapid growth stage. While higher EC levels suppress plant growth and should be used during the fruit production stage.
If the EC level is too low, simply add more nutrient solution to the water. If the EC gets too high, add more water to the reservoir. Since plants use different nutrients in varying degrees, the entire nutrient solution should be replaced periodically to insure that the proper mineral balance is maintained.
Also make sure that mineral salts don't build up in your hydroponic medium, particularly in ebb and flow systems. Flush the system periodically with fresh water to prevent the salts from building up to toxic levels.
Proper manipulation of EC and pH levels will insure that the root environment is ideal for nutrient and water uptake, providing the full benefits of nutrient control.
Let's take a moment to summarize
some of the most important factors that contribute to proper
nutrient control:
CO2 enrichment is beneficial to photosynthesis if enough
light is available to the plant.
Water quality should be slightly soft, without too high of a chlorine or bicarbonate level.
Oxygenation of the roots is important to plant respiration.
Increased nitrogen is beneficial at the vegetative growth stage.
Increased phosphorous and potassium are beneficial at the fruiting and flowering stage.
16 elements are "essential" to plant growth and reproduction.
Other elements are "beneficial" to the health and growth of plants, effecting the color and scent of flowers, and the flavor of fruit and vegetables.
Nutrient imbalances can harm the plant, resulting in deficiency or toxicity symptoms.
Toxicity in plants is generally more difficult to correct than a nutrient deficiency.
The pH of the nutrient solution should
be slightly acidic, adjusted to remain between 5.8 and 6.4.
EC levels should be low to medium during the vegetative
growth stage, and higher during the fruiting and flowering
stage.
If these simple guidelines are followed,
plant nutrition can be optimized in your hydroponic system,
resulting in stronger, healthier, more productive plants.
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