hydroponics nutrients

The first step in Hydroponics farming is to understand the difference between soil fertilizers, and the requirements of plants. Most growers are aware of soil fertilizers such as those called by numbers 19-19-19 and 20-20-20, but what does 20-20-20 really mean?

Does it mean 20% Nitrogen (N), and 20% Phosphorous (P), and 20% Potassium (K) is the N.P.K ratio?

No, it’s not that simple.

It’s, 20% Nitrogen (N) and 20% Phosphorous Pentoxide (P2O5) and 20% Di-Potassium Oxide (K2O). (Depending on the country of origin, these units change by continent)

This translates to the actual % of the N.P.K as follows.

20% Nitrogen (N), 8.8% Phosphorous (P), and 16.6% Potassium (K).

However, a good Hydroponic nutrient contains all of these plus all the other minerals required for healthy growth. They will also be in the correct ratio to each other, according to plant type, and stage of growth, e.g. Vegetative, flowering or fruiting stage. 

The minerals required for good growth are as follows:

 

 

 

 

 

 

 

 

 

 

 

There are other minerals found in plant tissue when analysed, but for our purposes, these are the main requirements for Hydroponic growing, and the ones we have to monitor.

Hydroponics grower has to understand and make sure that the Hydroponics nutrients being used have all the above macro and micronutrients needed by the plant in a proportion that is needed at various stages of growth.

Take for example, the above 20-20-20 fertilizer with 20% Nitrogen (N), 8.8% Phosphorous (P), and 16.6% Potassium (K).

Researchers have determined that a tomato plant in fruiting stage needs more Potassium than Nitrogen with N:K ratio of even 1:3. Using 20-20-20 fertilizer for tomato crop in the fruiting stage might not give the best yield when compared to a Hydroponic nutrient modified in a proportion to suit the crop need.

Hydroponic farming gives best results only when the grower gives nutrients in the right proportion suiting crop, stage of growth, water pH, EC, climate conditions etc.

Plants are similar to us humans and animals in that when under stress from poor nutrition, our bodies suffer in growth, development, and general health. Animals show these disorders in the form of weak bones, skin discolouration, and poor weight. Plants show nutritional defects in their vigour, strength of the stems, colour of the leaves and poor yields.

Whenever plants undergo any type of stress from environmental conditions to lack or excess of nutrients, they will express signs of disorders. Pest and diseases also cause stress and disorders within the plant.

Symptoms of disorders within the plant may be expressed as leaf yellowing (chlorosis), browning (necrosis), burning (white colouration due to loss of chlorophyll in leaves), deformation of leaves and growing tips, and stunting of overall growth. The first thing to observe with a nutrient disorder is the location of the affected tissue.

 

 

 

 

 

 

Leaves will, in general, show the symptoms first. If it is a root problem due to disease or lack of oxygen, examination of the roots will reveal that they are not turgid and white, but limy and brown. The plant will wilt during high light periods as the water loss by transpiration is greater than the roots ability to take up sufficient water.

The location of symptoms on the plant is the first clue as to the cause of the disorder. Focusing on leaf symptoms, if the lower leaves are expressing yellowing, browning, or spots first, then the group of nutrients responsible for the disorder would be those of “mobile” elements. Mobile elements can be retranslated within the plant from the lower order tissue to the younger tissues in the top of the plant. These elements include N, P, K, Mg, Zn and Mo. Initial symptoms will be a yellowing (chlorosis) followed by browning or drying (necrosis) of leaf tissue. If the symptoms appear in the young leaves at the tip of the plant, this disorder is a result of a lack of “immobile” elements that cannot move from the older plant parts to the growing tip. These immobile elements are Ca, B, Cu, Mn, S and Fe. To determine which of these is the cause of the disorder there are some visual “keys” listed below allowing you to make a number of alternative choices. Each selection narrows the possible causes in the final step, there is a single element identified.

• It is critical to recognize any symptoms occurring at an early stage of the plants, expression of these stress clues because as the disorder goes on without correction, the symptoms expand progressing from simple yellowing spots to complete yellowing and necrosis. At that stage, it is very difficult to know the first form of symptoms as they spread throughout the plant giving it an overall chlorosis, necrosis, and deformation of tissues. In addition, as the stress becomes more severe, it will be difficult, taking a lot of time to correct it once identified. The loss of the plant’s health may become permanent or event result in its death. Yields will be greatly reduced as the stress is not corrected. The stress may begin as a cause from a single element and then as it progresses, another element uptake is slowed or blocked and the plant suffers from multiple disorders. A very useful procedure when a symptom first appears is to immediately change the nutrient solution. That is, make up a new batch. At the same time, to determine the exact cause send a nutrient or tissue sample to a laboratory for analysis. Similar to soil analysis, the laboratory will give you guidelines as to what the normal leaves of each nutrient should be in the solution or in the plant and direct you to make adjustments in the nutrient solution formulation.

Mobile Elements Deficiencies: -   

Nitrogen: -

• Lower leaves become yellowish green and growth is stunted

Remedies: -

• Add calcium nitrate or potassium nitrate to the nutrient solution.

Phosphorous: -

• Stunted growth of the plant, a purple colour of the undersides of the leaves is very distinct and leaves fall off prematurely.

Remedies: -

• Add monopotassium phosphate to the nutrient solution.

Potassium: -

• The leaflets on older leaves of tomatoes become scorched, curled margins, chlorosis between veins in the leaf tissue with small dry spots. Plant growth is restricted and stunted. Tomato fruits become blotchy and unevenly ripen.

Remedies: -

• Apply a foliar spray of 2% potassium sulfate and add potassium sulfate to the nutrient solution.

 Magnesium: -

• The older leaves have interveinal (between veins) chlorosis from the leaf margins inward, necrotic spots appear.

Remedies: -

• Apply a foliar spray of 2% magnesium sulfate, add magnesium sulfate to the nutrient solution.

Note: - When applying foliar sprays, if in a greenhouse, avoid doing during high sunlight conditions as that can cause burning of the leaves. Apply in the early morning while the sun and temperatures are low.

 Zinc: -

• Older and terminal leaves are abnormally small. The plant may get a “bushy” appearance due to the slowing of growth at the top.

Remedies: -

• Use a foliar spray with1%-0.5% solution of zinc sulfate. Add zinc sulfate to the nutrient solution.

 Immobile elements: -

• First, the symptoms appear on the younger leaves at the top of the plant.

 Calcium: -

• The upper leaves show marginal yellowing progressing to leaf tips, margins wither, and petioles curl and die back. The growing point stops growing and the smaller leaves turn purple-brown colour on the margins, the leaflets remain tiny and deformed. Fruit of tomatoes shows blossom-end rot.

Remedies: -

• Apply a foliar spray of 1.0% calcium nitrate solution. Add calcium nitrate to the nutrient solution.

 Sulfur: -

• Upper leaves become stiff and curl down, leaves turn yellow. The stems, veins and petioles turn purple and plant growth is restricted.

Remedies: -

• Add potassium sulfate or other sulfate compounds to the nutrient solution. A sulfur deficiency is usually rare because it is added to the nutrient solution by use of potassium, magnesium, and other sulfate salts.

 Iron: -

• The terminal leaves start turning yellow at the margins and progress through the entire leaf leading eventually to necrosis. Initially, the smallest veins remain green giving a reticulate pattern. Flowers abort and fall off, growth is stunted and spindly in appearance.

Remedies: -

• Apply a foliar spray with 0.02%-0.05% solution of iron chelates every 3-4 days. Add iron chelate to the nutrient solution.

 Boron: -

• The growing point withers and dies. Upper leaves curl inward and are deformed having interveinal mottling (blotchy pattern of yellowing). The upper smaller leaves become very brittle and break easily.

Remedies: - 

• Apply a foliar spray of 0.1%-0.25% borax solution. Add borax or boric acid to the nutrient solution.

 Copper: -

• Young leaves remain small, margins turn into a tube toward the midribs in tomatoes, petioles bend downward, and growth is stunned to get a “bushy” appearance of the plant at the top.

 Remedies: -

• Use a foliar spray of 0.1% - 0.2% solution of copper sulfate. Add copper sulfate to the nutrient solution.

Note: - whenever applying a foliar nutrient spray, apply it first to a few plants and wait to apply it to all plants for about a day to be sure that no burn occurs from the spray.

Manganese: -

• Middle and younger leaves turn pale and develop a characteristic checkered pattern of green veins with yellowish interveinal areas. Later small necrotic spots form in the pale areas. Shoots will become stunted.

Remedies: -

• Apply a foliar spray of 0.1% manganese sulfate solution. Add manganese sulfate to the nutrient solution.

Molybdenum: -

• All leaves show a pale green to yellowish interveinal mottling. Usually progresses from the older to the younger leaves.

Remedies: - 

• Apply a foliar spray of 0.07%-0.1% solution of ammonium or sodium molybdate. Add ammonium or sodium molybdate to the nutrient solution.

“It’s not what you eat, it’s what you absorb,” a phrase that applies equally to the uptake of essential nutrients by plants. Application of an essential plant nutrient does not always mean that the plant will be able to uptake that mineral and then move it through the vascular system into the plant tissues.

The availability of plant nutrients is in fact dictated by the form of the mineral, environmental temperature, humidity, photosynthesis, pH of the root zone, and most importantly the relative concentration of each mineral in the nutrient solution. It is the balance of these minerals that are often forgotten when growers are formulating plant nutrient recipes and adding supplements to reach specifically targeted mineral compositions.

There is a well-known system that classifies essential plant nutrients into “macro” and “micro” categories based on their concentrations in the plant tissue. Less understood is the relationship of the electrical charge of the individual ions and how it affects their bioavailability to the plant. Ions exist as either positively charged (cations) or negatively charged (anions) depending on the balance of electrons (negative) versus protons (positive). It is the strength of the ionic charge that will affect the movement of the ions into and out of the plant. By understanding the strength of the positive or negative charge of essential plant nutrients, we can begin to comprehend the selective ion uptake mechanisms of a plant’s physiology. The table below shows the elemental forms of plant nutrients and their ionic charges in the forms that are available for plant uptake.

The movement of ions into plant roots occurs by both active and passive transport. Passive transport means that the ions are carried with the uptake of water into the plant without energy from the plant. The water movement factors that affect passive transport are temperature, humidity, photosynthesis rates, the concentration of ions in solution versus within the plant cell, and plant transpiration rates based on the stage of growth. Active transport requires energy from the plant and ion movement is determined by competition between ions based on their individual charge. The monovalent ions (single charged) are moved into the plant more easily than divalent ions (double charged), while divalent ions are taken up more easily than trivalent ions (triple charged). This means that the plant will accumulate more potassium (a monovalent ion) than calcium and magnesium (divalent ions) due to the difference in their charge. Plants typically maintain a negative interior (inside the plasma membrane) relative to the exterior. The slightly negative state of the cell interior and the environment must be maintained and, thus, is related to ion uptake. When there are more cations than anions present, the overall charge becomes excessively positive, and an increase in anions or a decrease in cation uptake occurs to restore physiological conditions. For example, an excess of ammonium (NH4+) cations decreases the uptake of potassium (K+), calcium (Ca2+), and Magnesium (Mg2+). The same relationship exists for anions - excess anions lead to a lower uptake of anions or an increase in cations to balance the cell’s charge. If nitrate (NO3-) is the major anion in excess, then the uptake of cations such as potassium (K+), calcium (Ca2+), and Magnesium (Mg2+) will increase to compensate for the overall negative charge caused by excess nitrate levels.

Many growers give themselves labels based on the types of inputs they use in their gardens, often referring to “strict organic practices” or “sterile, mineral-based hydro”. Perhaps you’re the type of gardener who avoids “chemicals,” or only uses “organics”, but can you define these terms? What makes something truly organic? Every grower should understand what they put into their gardens and why.

What is a chemical?

When we use words like chemicals or chemistry, we are simply referring to the study and use of elements from the Periodic Table. The elements found in the Periodic Table are the basic atoms that make up everything on this planet and many chemicals that exist in the natural world. All Plants produce chemicals throughout their life cycle. In an organic garden, we rely on microorganisms to convert organic matter into chemical forms that are taken up by plants. Chemicals can originate from natural sources. In some respects, organic gardening is a natural way of feeding chemicals to plants.

So, the next logical question: What is Organic?

Chemists and physicists will tell you that nearly any compound containing carbon is organic, whether that compound is natural or not. The truth is many natural substances are not organic. For example, certain types of naturally occurring rocks are crushed to make fertilizers that contain inorganic phosphorus. Those rocks are technically inorganic, even though they were mined directly from the ground. Many gardeners and agricultural professionals use the word organic to describe fertilizers and plant products that are derived exclusively from plants and animals (manure, kelp, bone meal, etc.). By that definition of the word, Organic growers cannot use inorganic substances, even if they occur naturally.

One thing to keep in mind: many organic garden products contain inorganic salts. Two popular examples are bat guano and seaweed extract. Because these are derived from animals and plants, they qualify for organic gardening. However, the lab analysis shows a dash of inorganic material included in the final products.

Confused yet?

What are Minerals?

The Periodic Table contains (among other things) the 17 elements required for plants to live: carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, boron, chlorine, copper, iron, manganese, molybdenum, nickel, and zinc. Many scientists and university studies give evidence that silicon should be added to that list as well. Minerals occur in nature, but they are not sourced from plants or animals. These minerals may come from crushed rocks, or they may be generated in a lab via chemical processes. When looking at basic elements and minerals, there is no difference between the crushed rock form and the laboratory derivative. It may take millions of years to accumulate rock formations, which then have to be mined and pulverized, so the laboratory version is much faster. Mining can be quite harmful to the environment, not to mention, expensive and unsafe for workers. Depending on the specific element, one method may be better suited than another for obtaining these minerals with the least environmental and budgetary impact.

In recent years, there has been increased discussion regarding the use of high-quality or low-quality minerals in plant foods. The real difference in quality can be determined by the level of contaminants in the final product. Pure, uncontaminated elements are the same, regardless of the source. Elements and compounds that are not available to plants can bog down roots and slow nutrient absorption and availability. For the highest quality mineral plant foods, avoid contaminants and questionable ingredients.

Reasons for using organics

There is little argument that mineral fertilizers can more easily burn plants if used carelessly. Overfeeding is always a concern, but is less likely when using organics. Microbes and fungi must work to convert elements into plant available forms, which slows reactions in the root zone as it becomes nutrient rich. While overfeeding with organics is possible, the microbiology at work in the root zone offers a natural buffer. The flavour of organically grown tomatoes, culinary herbs, and resin-producing plants is often said to be better and more complex than crops grown with minerals. The fact is that low-quality or high-quality harvests can be grown with either mineral or organic inputs. One reason why well maintained organic gardens often produce very deep aromas and flavours is, in part, because overfeeding has been avoided.

Reasons for Using Minerals

We live in an age where plant chemistry and biology have been analyzed to an exacting degree. Scientists have discovered which elements are taken up by plants, and the specific ratios required for optimum performance. Mineral nutrient formulations can be made using highly available forms, allowing plants to absorb them right away. This process can lead to faster growth, bigger harvests, and increased quality. Many hobby gardeners grow delicious tomatoes in their backyards, using mineral salts from the local garden centre. Even without organics, mineral-grown crops can offer increased flavours and aromas, as long as the grower does not over-use plant foods or harvest prematurely. Attention to detail is required when using mineral fertilizers, and there is no need to sacrifice quality by overdosing plants. When given the correct amounts of mineral inputs, plants can achieve optimum health. Overall plant health is the key to both higher yield and quality.

Hybrid Nutrient Systems

Growers all over the world have achieved big yields and potent flavours by using organics and minerals together. Both offer unique benefits, and there is no reason you can’t use them in tandem to get the best of both worlds.

Many naturally occurring inorganic compounds are not only safe for plants, they are safe enough for you to eat! Don’t reject the idea of using organics, minerals or both before doing some research on the pros, cons and effectiveness of each type of nutrient.

What are you feeding your plants?

Not every garden product should be assumed to be safe or effective. Learn about the elements your plants require and the additional organic inputs that offer increased quality. With a little bit of knowledge and high-quality plant nutrients whether organic, mineral, or both, your garden will flourish!

 

Potassium is a paramount macro-element for overall survival of living things. It is an abundant mineral macronutrient present in both plant and animals tissues. It is necessary for the proper functioning of all living cells. Potassium is relatively abundant in the earth's crust making up to 2.1% by weight. Potassium is mined in the form of potash (KOH), sylvite (KCl), Carnallite and Langbeinite. It is not found in free nature.

Importance of potassium to plants

Potassium is an indispensable constituent for the correct development of plants. It is important in photosynthesis, in the regulation of plants responses to light through opening and closing of stomata. Potassium is also important in the biochemical reactions in plants. Basically, potassium (K) is responsible for many other vital processes such as water and nutrient transportation, protein, and starch synthesis.

Potassium Uptake

Bio-availability and uptake of K by plants from the soil vary with a number of different factors. The rate of respiration by plants is largely the determining factor for proper uptake and transport of potassium by plants. Its uptake is dependent on sufficient energy (ATP). Potassium plays a vital role in the translocation of essential nutrients, water, and other substances from the roots through the stem to the leaves. It is also made available through fertilizers in the form of K2O. Plant tissues analyze the form of these fertilizers and convert it into a more bio-available form. It is absorbed in the form of ions- K+.

Functions of Potassium in plants

Potassium (K) essentially plays a major role in plant physiological processes. Therefore, it is required in large amounts for proper growth and reproduction in plants. It is considered vital after nitrogen as far as nutrients needed by plants are concerned. It is also termed "the quality nutrient" for its contributing factor in a number of biological and chemical processes in plants. Here is why Potassium is important in plants:

• Potassium regulates the opening and closing of stomata thus regulating the uptake of CO2 thus enhancing photosynthesis.
• It triggers activation of important biochemical enzymes for the generation of Adenosine Triphosphate (ATP). ATP provides energy for other chemical and physiological processes such as excretion of waste materials in plants.
• It plays a role in osmoregulation of water and other salts in plant tissues and cells.
• Potassium also facilitates protein and starch synthesis in plants.
• It activates enzymes responsible for specific functions.

Potassium deficiency in plants

Regardless of its availability from soils, potassium deficiency may occur and might start from the lower leaves and progress towards other vital parts of the plants. Deficiency might cause abnormalities in plants affecting reproduction and growth. Severity depends on with the type of plant and soil. Some of the potassium deficiency symptoms may include:

• Chlorosis: May cause yellowing of leaves, the margin of the leaves may fall off, and also lead to shedding and defoliation of the leaves.
• Stunted growth: Potassium being an important growth catalyst, its deficiency or insufficient might lead to slow growth or poor developed roots and stems.
• Poor resistance to ecological changes: Reduced availability of potassium will directly result in less fluid circulation and translocation of nutrients in plants. This will directly make plants susceptible to temperature changes.

Importance of potassium in agriculture

Potassium is important in agriculture and soil gardening. It is used as a constituent in artificial fertilizers. Potassium fertilizers have been seen to increase crop yields, enhance production of grains rich in starch and protein content of plants. Additionally, potassium fertilizers may help improve plants immunity to weather changes, diseases, and nematodes.

Potassium is majorly used in hydroponics to improve root growth and enhance drought tolerance. It also enhances the building of cellulose and thus reduces lodging.

Cherry Tomato: - 

Tomatoes are an excellent summer fruiting vegetable to grow using all available methods although physical support is necessary.

A higher nitrogen concentration is preferable during the early stage to flower stage. However, potassium should be present from the flowering stage to fruit setting to growth.

Tomatoes are rich in vitamins A and C, low in calories and a source of lycopene (the “Red” in tomatoes), which has been tapped as a cancer-fighting agent.

If you have experience in growing tomato you know that to get the high-quality products and good yields with a limited space can be quite a challenge.

We’ll try to consolidate all important things that you need to know if you want to grow tomatoes, have high-quality products and great yields in your greenhouse. We’ll also share our experience and you’ll see great benefits of aquaponic systems for profitable commercial tomato production.

Tomato is one of the most demanded vegetables. In the season but also out of the season. It is used as a fresh produce but also an input for the production of many different products like sauces. One of the greatest advantages is that it grows in the air and we can use a lot of greenhouse height for our production.

The main advantages of growing tomatoes in protected spaces (greenhouses) compared to other crops are:

• It is highly attractive and demanded product
• We can have very high yields per sqm
• There are many hybrids that are resistant to diseases.

Growing Conditions: -

• When you have set up your aquaponic system and decided to grow tomato you need to pay attention to some details. If you make mistakes, in the beginning, you will not see problems usually until it’s too late to fix them.

1. Type of aquaponic system?
2. How to band tomatoes for the best vertical growth?
3. How to make tomato grow faster?

• Each and every part of the aquaponic system that is not synched to specific natural laws can create problems in the future. These problems can be insignificant but sometimes these problems can lead to total disaster. For that reason, it is important to have all the information and to understand each part of the system.
• The first and most important factor is to choose the right aquaponic system for tomato production.
• Out of all aquaponic systems, BED system is probably the most convenient for many types of crops. But it is not a profitable system. Because it is quite robust, it takes a lot of space and is quite expensive to construct.
• For profitable tomato cultivation, one of the best aquaponic systems is DUTCH BUCKET

• In Dutch bucket aquaponic system we are using a number of buckets for growing our crops in them. In buckets, we put any growing media that is suitable for aquaponics. When we are irrigating crops the water is moving through growing medium and feeding the root of our plants.
• We need to make sure that there is always some water in the bottom of the bucket.
• We can achieve this by drilling drainage holes on a certain height of the bucket. For this system to work we do not need any additional siphons.
• When constructing Dutch bucket aquaponic system pay special attention to the following

1. Greenhouse space usage
2. Pipes and nozzle clogging
3. Space for roots development
4. Bucket drainage

• Tomatoes prefer warm temperatures with full sun exposure. Below 8-10°C, the plants stop growing, and night temperature 13-14 encourage fruit set. Temperature above 40°C cause floral abortion and poor fruit setting.
• Tomatoes have a moderate tolerance to salinity, which makes them suitable for areas where pure freshwater is available. However, higher salinity at fruiting stage improves quality of the products.

Planting Instructions: -

• Set stakes or plant support structures before transplanting to prevent root damage.
• Transplant the seedlings into units 3-6 weeks after germination when the seedling is 10-15 cm and when the night time temperatures are constantly above 10°C.
• In transplanting the seedlings, avoid waterlogged conditions around the plant collar to reduce any risk of diseases.
• Once the tomato plants are about 60 cm tall, start pruning the unnecessary upper branches. Remove the leaves from the bottom to 30cm of the main stem for better air circulation and reduce fungal incidence.
• Remove the leaves covering each of the fruiting branches soon before ripening to favour nutrition flow to the fruits and to accelerate maturation.

Harvesting: -

• Most cherry tomato plants will start flowering in about a month. Flowers will be followed by tiny green fruits. After a few weeks, those turn into full-blown cherry tomatoes you can harvest.
• A truly ripe cherry tomato will come off its stem very easily and is well worth waiting an extra day for, so hold off on picking them until they're ripe. Then, pluck individual fruits every day for best results. With luck, your plant will continue to produce right up until winter. If the weather turns unseasonably cool or an early frost threatens, you can tuck an old sheet over and around the plant to extend your harvest season.
• Fruits can be easily maintained for 2-4 weeks at 5-7°C under 85-90 percentage relative humidity.

Tips: -

• PH: 5.5-6.5
• Plant spacing: 40-60cm (3-5 plants/sqm)
• Germination time and temperature: 4-6 days and 20-30 °C
• Growth time: 50-70 days till the first harvest; fruiting 90-129 days up to 8-10 months.
• Optimal temperature: 13-16°C night, 22-26 °C day
• Light exposure: full sun
• Recommended methods: Media Beds and DWC

• Growing hydroponics lettuce is one of the easiest and the best ways to start hydroponic gardening.
• Lettuce is a simple to grow all round plant that can ensure you get great results when grown in soil, as long as you keep pests off it.
• This is where growing lettuce hydroponically will make perfect sense and will be a terrific first task for any hydroponic setup.
• Lettuce hydroponics will typically look after themselves and do not need a lot of nutrients as other heavy feeding plants like tomatoes.
• It’s obviously still a great practice to check out your growing hydroponic lettuce plants every day for pests or other problems, though these problems are considerably decreased with hydroponics, particularly indoor hydroponics.
• Actually, the only issue you could come across when growing hydroponic lettuce at home is size.
• Lettuce is in high demand and has a high value in urban and peri-urban zones, which makes it a very suitable crop for large-scale commercial production.

Note: -

• Check lettuce for signs of downy mildew, powdery mildew or gray mold and get rid of any infected plants.
• Water that’s heavily chlorinated can lead to issues with lettuce. You should use lightly chlorinated city water or well water.

Lettuce varieties: -

Lettuce can be characterized based on their leaf and head formation.

Crisp head or iceberg: -

• Crisp head lettuce, more commonly known as iceberg, has a tight head of crisp leaves. Often found in the local salad bar, it is actually one of the most difficult lettuce varieties to grow. This lettuce variety is not fond of hot summer temperature or water stress and may rot from the inside.
• Start iceberg lettuce via seed directly sown 18-24 inches apart or started indoors and then thinned 12-14 inches between heads. Some iceberg lettuce varieties include Ballade, Crispino, Ithaca, Legacy, Mission, Salinas, Summertime and Sun Devil, all of which mature in 70-80 days.

Romaine or Cos: -

• Romaine varieties are typically 8-10 inches tall and upright growing with spoon-shaped, tightly folded leaves and thick ribs. Colouration is medium green on the exterior to a greenish white inside with the outer leaves.
• Sometimes being tough whilst the interior foliage is tender with wonderful crunch and sweetness. Different types of this lettuce are Brown Golding, Chaos Mix black, chaos Mix white, Devil’s Tongue, Dark green Romaine, De Morges Braun, Hyper Red Rumple, Little Leprechaun. All of which mature within around 70 days.

Butterhead, Boston or Bibb: -

• One of the more delicate varieties of lettuce, Butterhead is creamy to light green on the inside and loose, soft and ruffled green on the exterior. These different types of lettuce may be harvested by removing the entire head or just the outside leaves and easier to grow than crispheads, being more tolerant of conditions.
• Less likely to bolt and rarely bitter, the butterhead lettuce varieties mature in about 55-75 days and spaced similarly to the crispheads. These varieties of lettuce include Blushed Butter Oak, Buttercrunch, Carmona, Divina, and Yugoslavian red.

Growing Conditions: -

• Lettuce is a winter crop. For head growth, the night air temperature should be 3-12°C, with a day temperature of 17-28°C.
• The generative growth is affected by photoperiod and temperature extended daylight warm conditions(>18°C) at night cause bolting. Water temperature >26°C may also result in bolting and leaf bitterness.
• The plant has low nutrient demand; however higher calcium concentrations in water help to prevent tip burn in leaf in summer crops.
• The ideal PH is 5.8-6.2. but lettuce still grows well with a PH as high as 7, although some iron deficiencies might appear owing to reduced bio-availability of this nutrient above neutrality.

Growing instructions:

• Seedlings can be transplanted in units at three weeks when plants have at least 2-3 true leaves. Supplemental fertilization with phosphorous to the seedlings in the second and third weeks favours root growth and avoids plant stress at transplant.
• Take care not to damage the roots of plants during transplanting because such damage will make the plant susceptible to disease infection.
• It is advisable to transplant the plant in the late afternoon to prevent them becoming stressed in the heat of the day under high UV conditions.
• The transplant will begin to adapt to the new location at night and roots will start to grow into the solution below.
• Make sure the plants base is touching the flow of nutrient solution below when transplanting.
• To achieve crisp sweet lettuce, grow plants at a fast pace by maintaining high nitrate levels in the unit. When air and water temperatures increase during the season, use bolt -resistant(summer) varieties. If growing in media beds, plant new lettuces where they will be partially shaded by taller nearby plants.

Lighting: -                                      

• Lettuce grows up vigorously with fluorescent lighting. It would obviously grow far better with the more expensive lighting specially created for hydroponics, like HID and some of the latest LED grow lights for indoor plants.
• However, regarding cost-effectiveness, from the viewpoint of the small-scale grower, fluorescent lighting is the best.
• These are cool weather crops, so too much heat can, in fact, delay germination.

Harvesting Hydroponics lettuce: -

Hydroponics harvesting depends on the following factors

• First, this will depend on what type you are growing. Romaine takes up to 85 days. Bibb and Loose-leaf lettuce can take 45 to 55 days.
• It has to do preference, growing lettuce indoors then you have to manage the environment and prolong your harvest.
• The majority of hydroponic lettuce production systems created around two ideas, either the floating raft system or the nutrient flow technique (NFT) system.
• The floating raft method is of particular interest since it is very affordable and can produce a lot of hydroponic lettuce.
• One of the major issues with raft systems is that the hydroponic lettuce nutrients solution is continually stagnant and will require that you use pumps to circulate water and produce important aeration.
• If the roots are not getting the precious oxygen, floating raft systems experience substantial loses of crops in the form of nutrients.

Below are some types that work well in hydroponics and with indoor artificial lighting:

• Royal Oakleaf is a darker green variety of lettuce that does extremely well in hydroponic growing systems and is also resistant to heat.
• Tango grows perfectly in cooler environmental only.
• Red Fire is a deep red, loose leaf variety that’s ideal for both warm and cool climates.
• Green Ice is a variety of green loose that offers a long picking season.

Hydroponic romaine lettuce also does well though it usually takes a little bit longer to attain maturity.

Tips: -

• When you harvest lettuce with the roots attached, it will prolong storage life by two to four weeks.
• To prevent getting water mold such as Pythium or Phytophthora in your hydroponic lettuce system, use bleach to sanitize the tray between plants. If the lettuce gets infected, the plant is a loss.

 

 

 

 

What is pH?

pH is a measure of the relative concentration of hydrogen ions (H+) to hydroxide ions (OH-). The greater the number of H+ ions in relation to OH- the more acidic the solution becomes. The greater the ratio of OH- ions to H+, the more basic the solution becomes. PH is measured on a scale of 1-14. A reading below 7 means that there are more H+ ions and a reading above 7 indicates more OH- ions. At pH 7 there are the same number of H+ ions as OH- ions so the pH is neutral, neither acid nor base.

 

 

 

 

 

 

 

 

 

Acids and Bases

Any substance that increases the concentration of hydrogen ions (lowers the pH) when added to water is called an acid. A substance that reduces the concentration of hydrogen ions (raises the pH) when added to water is called a base or an alkali. Some substances enable solutions to resist pH changes when an acid or base is added. These substances are called buffers. Buffers are very important in helping to maintain a relatively constant pH in a feeding solution and in the root zone after the water has been applied to the crop. Most greenhouse water supplies have sufficient alkalinity that they require routine acid addition to correct the pH to the normal 5.8-6.2 feeding range. At this level, the irrigation water tends to have a neutral effect on media pH, although this depends on the buffering capacity of the media. Some growers use very pure water from rain and surface sources. In these situations, they may need to apply a combination of acid and base materials to stabilize and buffer the pH.

Why does pH Matter?

Improper management of media pH can result in poor growth and reduced plant quality in greenhouses and nurseries. The pH or soil reaction has a primary influence on the solubility and availability of plant nutrients. Many crops have a narrow range of pH tolerance. If the pH of the soil medium falls above or below this tolerance zone, they may not grow properly due to nutrient deficiency or toxicity.

The availability of most fertilizer elements is affected to some extent by the media pH. Calcium and magnesium become more available as the pH increases, while iron, manganese, and phosphorus become less available. A one-unit pH drop can increase the solubility of manganese by as much as 100 times, and the solubility of iron by as much as 1000 times.

Why Adjust Irrigation pH?

By carefully modifying the pH and alkalinity of your irrigation and feed solutions, you can help maintain the desired plant growth and quality. There are other reasons to monitor and control pH in your irrigation water and nutrient solutions: 1) Solution pH affects the availability of nutrients. 2) Correct pH helps ensure dissolved fertilizer concentrates remain in solution when mixed in the water supply. 3) Acid injection can be used to neutralize excess alkalinity in water supplies.

Understanding The pH Scale

The pH scale measures the relative concentration of Hydrogen Ions (H+) and Hydroxyl ions (OH-) in a solution. Technically, the pH of a solution is defined as a negative logarithm of the hydrogen ion concentration. The ‘p’ is the mathematical symbol for a negative logarithm and the ‘H’ is the symbol for hydrogen. The pH scale measures this, and places a value on it ranging from 0 to 14. Since it is a log scale, each number on the scale is 10 times greater (or smaller) than the next. A lower pH number corresponds to a higher concentration of hydrogen ions (H+) relative to hydroxyl ions (OH-). A higher pH number corresponds to a relatively lower concentration of hydrogen ions

Measuring pH

There are several methods available for measuring pH, but the most useful and practical is an accurate pH meter. Follow the instructions included to preserve the accuracy and life of your instrument. These meters typically use a liquid filled glass probe, although some are now using flat sensor technology.

Water and nutrient solution samples can be measured directly or preferably after a few hours of settling time. Dissolved CO2 in water supplies can cause slightly lower readings until the sample has come to equilibrium with the air. When testing media, freshly mixed samples of media should be watered and allowed to stand for 24 hours before a reading is taken to release some of the lime and fertilizers. The preferred method for testing media pH is to obtain several representative samples of a crop and to measure each separately. Multiple measurements give greater accuracy in reading, and shows the degree of variability of pH across several locations. A saturated media extract or a 1:1 soil to distilled water ratio is fine for measuring media pH.

Factors Affecting pH

These variables can affect the final pH, the rate of pH change, and the amount of modifying action required. They include the effects of:

• Soil temperature
• Fertilizer materials (may raise, lower or buffer pH)
• Soil amendments such as gypsum, sulfur and lime
• Root volume & metabolic activity
• Soil microorganisms
• pH and alkalinity of the irrigation water
• Leaching fraction
• Buffering capacity of both the soil medium and the irrigation source
• Media cation exchange capacity

With all of the emphasis on N-P-K in agriculture, calcium and magnesium are sometimes overlooked. Calcium and magnesium are essential macro-elements, used in relatively large quantities. In fact, plants take up more calcium than phosphorus!

ROLES OF CALCIUM IN PLANTS

CALCIUM IN HYDROPONIC NUTRIENT SOLUTIONS

In hydroponic systems, adequate levels of calcium are usually maintained with calcium nitrate or other calcium salts. Therefore the lowering of calcium levels in the plant tissue and the occurrence of deficiency symptoms usually result from the influence of other factors which impede either calcium uptake or its distribution within the plant. Calcium uptake may be reduced by the competitive effects of a high concentration of other cations such a potassium, sodium, magnesium or ammonium in the solution. And since calcium moves in the xylem tissue, its uptake is also affected by low root temperature and by restricted water movement through the plant caused by high salinity in the media or excessive humidity in the atmosphere.

Higher EC levels in the nutrient solution reduce the uptake of calcium, unlike nitrogen and potassium which increase in concentration in leaf tissue with higher EC levels. Reducing the EC of the nutrient enhances water uptake and with this, more calcium can be taken up and transported within the plant to developing tissue.

CALCIUM DEFICIENCY SYMPTOMS

REMEDIES

The simplest means of preventing calcium deficiency disorders such as tipburn and blossom end rot is to maintain adequate calcium levels in a balanced nutritional solution with the correct EC level. Use 0.75% - 1.0% calcium nitrate solution as foliar spray in acute cases. As always, moderation is always recommended when using additives. Start with very low dosages, see how the plants respond and add more if necessary. Keeping the plants stress free, providing gentle air movement across the leaf source to encourage transpiration and preventing excessive temperatures all help drive calcium into leaf tips and developing fruits.