Hydroponic Nutrient Management

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Posted by: dcyans Aug 02 03, 06:58 PM GMT


Choosing the right commercial nutrient solution for your application can be a bewildering and frustrating task. Sorting out the competing claims of manufacturers and the biases of various writers on the subject---some justified and some not---often leaves the beginning grower more confused than enlightened.
Unfourtunately for the neophyte grower, simply making the "right" choice is no ticket to successful hydroponic gardening. Yes, a quality, balanced nutrient solution is essential to getting the most from your high-tec garden. But in the long run, it is how you manage that solution and the system that will determine success or failure.
Beginners should always use the nutrients according to manufacturer's suggested dosage, usually one or two teaspoons per gallon. Experimentation has its place but if you are just starting out, resist the temptation. The freshly mixed solution should contain between 1,300 and 1,500 parts per million (ppm) of total dissolved solids (DS). These are the scientifically correct terms for the measurement of the actual strength of your nutrient and you should become familiar with them. Most suppliers of home hydroponic systems recommend that you maintain the solution level in your system by adding tap water. Then every two or three weeks they tell you to change the entire solution. Although this method is easy, it is not correct except for commercial sized systems.
The nutrient capacity of most home systems is to small to be replenished with only tap water. When your system feeds, the plants' roots are removing elements needed to support growth. As the plants grow and mature, they can deplete your nutrients in a matter of days.

Nutrient monitoring
I am sure many gardeners have found it necessary to change nutrient every three or four days to sustain flowering; some have probably even tried changing formulas. Both of these methods have been widely used with varying degrees of success and failure. If, however, you are serious about hydroponics and really do want to enjoy twice the yield as soil growers, you must take one more simple step ahead in technology. You should purchase any one of a number of nutrient testing devices and start monitoring your nutrient solution. This equipment will allow you to maintain the strength of your solution at the recommended 1,300 to 1,500 ppm. All serious hydroponic suppliers are using this type of equipment and should have it available for resale. These devices range in price from $1,000 for a complete portable lab, to $300 for a dissolved solids meter that instantly reads in ppm, all the way down to a simple phosphorus tester that sells for about $50. Any of this test equipment will enable you to accurately maintain the strength of your solution by adding small amounts of nutrients along with tap water evert day or two. You will still need to change the entire solution every two or three weeks to remove any excess plant wastes and allow you to keep your storage tank clean. IT is also a good idea to rinse your growing medium thoroughly every time you change nutrient. This one simple step ahead in the science of growing will assure better results in every size and type of hydroponic system. If your current supplier of hydroponics can't help you find this equipment, locate one who will.

Nutrient solutions
All hydroponic systems have one thing in common: the need for a complete and balanced nutrient formula. This, of course, brings us back to where we started. Your nutrient solution must contain all of the following: nitrogen (N), phosphourus (P), potassium (K), calcium, magnesium, sulfur, iron, copper, manganese, boron, zinc, molybdenum, and cobalt. Because of federal and state regulations, nutrients are sold and labeled according to the standard "NPK" three-number designation, such as 8-6-12. To the science of hydroponics these numbers have less significance than you might think. What really makes a nutrient formula correct is the balance, or ratio, of the different elements to each other and the solubility of the compounds. While nutrient balance and interaction is beyond the scope of this article, it is important for the fledgling grower to at least be aware of this nutrients and there function in the growing process. I recommend printing this article for easy reference as I have found it very helpful. Listed below are 11 key elements and some typical deficiency symptoms for each. It is important to note that a number of these symptoms, stunted plants for example, are listed under reveral different nutrients. Only through carful monitoring can tell you for certain the condition of your nutrient solution.
Also another quick tip (colt) wink.gif and I will mention this as many times as it needs to come up, measure (ppm) of your water supply first as your water will contain a ppm reading (from additives like chlorine and flouride) that will take away from your actual nutrient ppm reading. I've had an 800 ppm reading before so you need to compensate in order to get your nutrients in the 1,300 - 1,500 range. Your actual reading in this case would be 2,100-2,300 ppm wink.gif So keep this helpful hint in mind next time your mixing your nutes wink.gif

Nitrogen is a key element affecting plant growth and crop yields. It is absorbed by plants primarily in the form (NO3) and is used by plants to synthesize amino acids and form proteins. It is also required by plants for other vital compounds such as chlorophyll and enzymes. Too much nitrogen will produce lush plants with dark green foliage, few buds and will even stop buds from developing at all :-( . Nitrogen is a mobile element in plants which means any deficiency symptoms will appear first on the older leaves.
Nitrogen deficiency symptoms include:
*Slow growth and stunted plants.
*Foliage becomes yellow (chlorotic).
*"Firing" (browning) of tips and margins of leaves.

Phosphous stimulates early growth and root formation and is absorbed by plants as (PO4). It is used by plants to form nucleic acids, DNA and RNA, and is very important to the plant's energy transport system. It can hasten maturity and promote seed production. Phosphorus is also a mobile element and is greatly affected by temperture. Too much phosphorus will interfere with normal function of other elements such as iron, manganese and zinc.
Phosphorus deficiency symptoms include:
*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 bud production.

Potassium is taken up by plants in the form of potassium ions (K+) and tends to remain in ionic form within the cells and tissue. It is essential for translocation of sugars and for starch formation. High potassium levels are required for protein synthesis and bud production. It will increase the size and quality of the harvest and helps make plants more resistant to disease. Potassium is another mobile element in plants. Too much of it can induce a calcium or magnesium deficiency.
Potassium deficiency symptoms include:
*Older leaves develop marginal burning.
*Weak stalks.
*Slow growth.
*Forward curling of the leaves.

Calcium is absorbed by plants as the calcium ion (Ca++). It is essential for the formation and structure of cells. Calcium is non-mobile in plants which means that any signs of deficiency occur first in the newer leaves.
Calcium deficiency symptoms include:
*Shoot tips yellow and die back.
*Abnormal dark green foliage.
*New leaves distorted
*Root tips die and aquire black spots.

Magnesium is used by plants in the form of magnesium ion (Mg++). It is contained in the chlorophyll molecule which means it is essential for photosynthesis. It is also required for activation of many enzymes involved in the growth process.
Magnesium deficiency symptoms include:
*Yellowing of older leaves.
*Withering of leaves.
*Upward curling of leaves along margins.

Sulfur is used by plants as the sulfate ion (SO4). It may also be absorbed from the air. Sulfur is a constitute of amino acids which means it is essential for protein sythesis. It is also present in the oil compounds that are responsible for the characteristic odor of plants. The deficiencies appear similar to nitrogen except that the symptoms appear in the new leaves.
Sulfur deficiency symptoms include:
*New leaves appear light green to yellowish.
*Yellowing of the older leaves.
*Small spindly plants.
*Retarded growth and delayed maturity.

Iron is required by plants for chlorophyll synthesis. It activates biochemical processes such as respiration, photosynthesis and nitrogen fixing. Iron can easily combine with other elements and should be provided in a chelated form for hydroponic nutrient solutions.
Iron deficiency symptoms include:
*Yellowing between the veins of newer leaves.
*In severe cases, death of entire limbs may occur.

Manganese serves as an activator for enzymes and aids in forming chlorophyll. It also helps produce oxygen from water during photosynthesis.
Maganese deficiency symptoms include:
*Yellowing between the veins of leaves near the tip of the plant.
*Leaves may turn brown and drop off.

Boron is used to regulate the metabolism of carbohydrates in plants. It is a non-mobile element and a small but continuous supply is required at all growing points of the plants.
Boron deficiency symptoms include:
*Dieback of shoots and root tips.
*Young leaves appear thick and curled.
*Reduced bud developement.

Molybdenum is required by plants for the utilization of nitrogen. Plants cannot transform nitrate nitrogen into amino acids without it.
Molybdenum deficiency symptoms include:
*Yellowing of older leaves moving into newer leaves.
*Stunted plants.
*Some cupping or rolling of leaves.

Copper is an activator of several enzymes and also plays a role in vitamin A production. A deficiency interferes with protein production.
Copper deficiency symptoms include:
*Stunted growth.
*Poor pigmentation.
*Wilting and eventual death of leaf tips.

Other factors
The hobby gardener must remember that these symptoms were discovered under ideal conditions. There are many other simpler factors which affect plant growth. These other factors include:
*Ventilation is probably the most overlooked problem in controlled environment growing. Plants absorb nutrients when the water in which the nutrients are dissolved is respirated (evaporated) from the leaves. The better the ventilation, the higher the respiration rate is and therefore the rate of nutrient uptake is also higher.
Remember that ventilation means changing the air, not just blowing it around the room. You need to have an equal amount of fresh air blowing in as you have used air blowing out. The average commercial greenhouse can completely change the total volume of air every minute. This may or may not be possible in an indoor grow room.
*pH should be maintained in the range of 5.8 to 6.5. Too high or too low of a pH value in the solution (or in soil for that matter) can restrict nutrient uptake.
*Temperature of the nutrient solution should be in the range of 70 to 80 degrees at feeding time. Many nutrient elements, most notably nitrogen and phosphorus, are greatly affected by temperature and may not be available at all if the nutrient is too cold.
*Light---the higher the light level, the bigger the harvest.

This brings us to the final question. What do I do if I notice a problem with my plants?
If you are fortunate enough to already be growing in hydroponics, the answer is quite simple. Drain all the nutrient from your system and rinse the growing medium thoroughly with tap water at the correct pH and restart the system.
Remember, always use a high quality, proven hydroponic nutrient formulas. If you are still growing in soil, you are on your own bud. sad.gif

Posted by: colt122 Aug 02 03, 07:13 PM GMT
Nice run-down wink.gif

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