Whether yours is a homemade or a commercial nutrient, there will be times when adjustments are necessary. Formula adjustments are probably the trickiest part of hydroponics, and caution should be used at all times or you could destroy your entire crop in a matter of days.
If you are using a well-balanced, commercial nutrient and a correction is necessary due to a deficiency that you can't identify, a foliar spray may be the answer. You can make the spray from a very diluted mix of nutrient and water. The easiest method would be to make up one quart of nutrient solution at regular strength and then dilute it with water to a one-to-seven or even a one-to-ten ratio. Use a mister and spray the diluted solution on the leaves of the affected plants once a day for several days. The leaves will absorb it quickly and spreading of the symptoms should be reduced greatly in a short period of time. A foliar spray can probably solve many of your trace element deficiency problems.
A large-scale commercial grower will analyze the leaf tissue of his plants every few days and make adjustments as necessary. Because this requires a great deal of knowledge, time and money for equipment, it is impractical for the modest home grower. In fact, it needn't be all that important in a home system where you are experimenting with hydroponics, raising relatively small crops and changing your nutrient solution every three to four weeks. If you spend ten to fifteen minutes a day with your system, you will find that in a few months you will be able to read the signals given by your plants and be ready to make necessary changes to the nutrient. Like anything else that's worthwhile, tuning in to your plants takes time, but the rewards are great.
Figure /1. A foliar s/zray applied with a mister can ttsualij solve man} trace element deficiency problems.
Ordinarily, your home water supply will be quite satisfactory for hydroponics, but a few cautions should be given. Water from a water softener should not be used, as it will be far too alkaline. On the other hand, rain or distilled water would be fine, providing a reliable and inexpensive supply could be maintained. Tapwater is average and it will generally contain small amounts of trace elements that the plant can use if it requires them. Water that is too pure may have to be supplemented with slight increases of some trace elements, especially calcium and magnesium. If the water is very hard, you will need less calcium and magnesium but probably more iron, because iron becomes less available to the plant as the hardness of the water increases. For these reasons, it is a good idea to have an analysis done on your water supply at your local utility. If you obtain your water from a well or source other than a Public Works Department, you can contact your nearest Agricultural Department for an address to send in a water sample. Any analysis should include the content of calcium, magnesium, iron sulphate, chloride and carbonate. In any case, it's probably worthwhile to know what you are drinking and using in your home.
Many apartments and modern homes are hot and dry, and you should bear in mind that these conditions can cause as much as a fifty per cent decrease in the need for potassium. Under very humid conditions, where the light level is lower, your plants will require more potassium — as much as twice the normal amount. This is because photosynthesis is more difficult with a lower light level and potassium is necessary for photosynthesis.
One of the main problems in attempting to determine the cause of a specific nutrient deficiency symptom is that almost everything sounds the same. In fact, this is not so; there are small differences in each problem. Like a doctor, you must attempt to isolate the symptoms and study the case history. Even if you are only able to reduce the possible causes to two or three at first, you can then isolate the symptoms, weigh the factors leading up to the problem, further reduce the possibilities to one or two at most, and take remedial action. The following chart will help you do this.
Nitrogen Small, stunted plants with very large root systems;
leaves smaller and lighter in colour than normal; slow growth. Paleness will start at the tips of the lower leaves. If this deficiency continues, the foliage will continue to develop, but stems will be spindly, sappy and soft, flowering will be delayed, small fruit will grow and the plant will be more susceptible to disease.
Phosphorus Stunted plants with dark, dull and sometimes discoloured leaves, unusually hard stems, poor root system, and very little branching. Attacks lower, more mature leaves first. Occurs especially when nitrogen level is low.
Potassium In early stages, yellowing and curling of older leaves.
Newer leaves will begin to droop. Older leaves then become blotchy and scorched. Flowers are lackluster, and stems are soft. The plant will be more susceptible to diseases such as mildew and rust.
Calcium Underdeveloped roots are the first to be affected.
Younger leaves will be immobile and their edges will curl. Plants will be stunted and have dark, crinkly leaves. (See blossom end rot. Chapter 13.)
Magnesium Symptoms do not appear until the deficiency is well established. The plant will be stunted. Leaf veins will stay green while the remainder of the leaf turns yellow. Brown spots will appear and then the plant will dry out. Flowers will be slow to develop, if at all. Flowers that do grow will be lackluster.
Iron Tips of new leaves will become either pale or yellow, and this will spread inward. The leaf will likely turn blotchy from a lack of green pigment, eventually turning brown and drying out.
Manganese Poor blooming, weak growth. Leaves may turn yellow blotchy.
Boron Brittle stems, and immobile new leaves with brown tip
It is not necessarily true that you will encounter any or all of these imbalance problems. Because of your particular situation or environment, however, you may find that from time to time specific problems will arise. It is worth repeating that the watchword of hydroponics is experimentation, as much in problem solving as in developing a system that suits your needs.
The symptoms listed in this chapter are symptoms of element deficiencies. On the other hand, a toxic (poisonous) situation can be created when one or more elements are being supplied in excessive amounts. It is very unlikely that such a situation will occur if the reader follows with reasonable accuracy any of the hundreds of formulae available in books. It seems unnecessary to load the novice with information on toxicity that will likely never be needed. However, the real seeker of knowledge should consult Hydroponic Food Production, by Howard M. Resh.
Carbon dioxide is absolutely essential for plant growth. This gas is required for photosynthesis—turning light into energy. The optimum level of 0.15 per cent C02 in the air is required for most plants. The minimum requirement is 0.03 per cent, which can be used up very quickly in an enclosed indoor area. Studies show that the optimum level can provide up to 25 per cent of additional growth to your plants.
You can add more carbon dioxide to the air by renting a tank of C02 from soft drink manufacturers or purchasing a C02 generator, which bums propane to create the gas. The generator is best for large grow rooms or greenhouses. If you choose to rent a tank, you should use a timer and flow meter to ensure that the expensive gas is not wasted.
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