Hydroponics & Aquaponics

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: -Â

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, 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

Know your water to know your best water soluble fertilizer options.

Water quality is the single most important factor in determining solubility and nutrient availability for plants. It's especially important that you test for the key parameters like pH, TDS and EC if you have one of the following factors:

•  Borewell water
• Change in irrigation water source
•  Multiple sources of irrigation water
•  Recent flooding or droughts

The primary considerations when formulating and evaluating your plant nutrition program are:

1. Nutritional content of the water
2. Its effect on growing media pH
3. Its content of potentially toxic components

With today's soilless growing media, water's alkalinity is the main area of focus. Alkalinity is a measure of how much buffering the water will provide to the given growing media.
If alkalinity is too low, the growing media pH can plunge due to acidic influences like fertilizer, growing media components and plant root exudates. If this happens micronutrient toxicities can occur. Conversely, if alkalinity is too high, growing media pH can soar, leading to deficiencies in micronutrients, such as iron. In this case, you may be applying plenty of iron, but it becomes unavailable to the plant at higher growing media pH.
A thorough water analysis will measure the alkalinity of your irrigation water as well as many other elements. Having your water tested can make the difference between growing a good crop and growing a great crop!

The four main water types:

While it's important to get complete water analysis of your irrigation supply, you can base your fertilizer choices on your water type category and the plants you're growing.

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.

Welcome to Hydrilla.....