Growing hydroponically

[NPK Technology]

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We wrote this for our website blog, we thought it might be nice to share it with all of you. Hope you enjoy


Imagine the first juicy bite of a perfectly ripened, locally grown, fresh summer tomato. Now, imagine foregoing those grainy, artificially ripened tomatoes from the grocery store and enjoying the unmatched goodness of homegrown tomatoes all year round. You can make that dream a reality by growing hydroponic tomatoes right in your own home. Growing tomatoes hydroponically allows you to monitor and control the lighting, temperature, and nutrients that the plants receive, thus controlling the flavor, sweetness, and nutritional value produced by the plants. Even the extreme novice can successfully produce fresh, succulent tomatoes with a little background information and technique tips.

Starting Hydroponic Tomato Seeds
It is highly recommended to begin with seeds rather than plants as plants can be contaminated with disease or pests. Rockwool starter cubes and standard dome nursery trays are a great start. Soak the rockwool cubes in water with a pH of 4.5. Plant the seeds. Keep trays covered and in a damp setting that remains consistently between 20 and 25 degrees Celsius (68°-77°F) until the plants start to sprout. As soon as vegetation shows, the seedlings should be moved to a light source for a minimum of 12 hours each day. Make sure that the roots never gain light exposure as this can stunt growth and even kill the roots completely. When leaves have sprouted and the roots are visible at the bottom of the rockwool cubes, the plants can move into their new hydroponic home.

Types of Hydroponic Systems For Tomatoes
Choosing the right hydroponic grow system depends on space availability, the type of tomato, and the size of the plants. Deep water culture (DWC) is most often used for the cultivation of only a few plants as it is fairly tedious to maintain. Generally, in a DWC system, one plant is grown per pot. A clay pebble growing medium is used. The water and nutrient mixture must start out at a high enough level to saturate the clay. After the root system is established, the water level should be lowered so that most of the roots are well into the water, but so that a few are in the empty space between the water level and the container. An air stone is used to aerate and mix the nutrient-rich water and should always run 24 hours a day. The pH in this type of system tends to naturally fluctuate, so it should continuously monitored.

If you have not had much experience with hydroponics, the nutrient film technique (NFT) may be the setup that you most recognize. Consisting of only a grow tray or tube, a nutrient reservoir, an air pump and stone, and a nutrient pump, it needs no timer and no growing medium. The nutrient pump carries the solution to the grow tube. The plants are usually contained in baskets and the roots dangle directly into the solution. The solution flows down the tube and back into the continuously aerated reservoir. The roots will dry out very quickly if the flow of nutrients is broken, so this type of system leaves the plants extremely susceptible to pump malfunctions or power outages.

For larger plant systems and commercial growing, a drip irrigation system is often used. In this type of system, a nutrient solution is pumped through an automated system that drips the solution onto the plants and re-circulates it. Plants and starter cubes are placed directly into individual pots that are each connected to the nutrient reservoir and haydite rocks are used to sufficiently aerate roots in a confined space.

Aeroponics is perhaps the most sophisticated technique. In an aeroponic system, the root systems are suspended in the air above the nutrient solution. The nutrient pump is controlled by a timer that periodically mists the roots with the solution. The timing and proper functioning of the pump is critical. There is little room for error using this method of hydroponics as clogged sprayers and pump failures can ruin a crop very quickly. It should also be noted that, in my knowledge, there are no large scale commercially grown aeroponic tomatoes.

Hydroponic Tomato Nutrient Requirements
The water quality and the nutrient solution are the key factors to successful hydroponic tomato cultivation. The pH of the water should remain between 5.0 and 7.0 at all times for optimal nutrient absorption. The pH of the nutrient solution should be between 5.5 and 6.0. The electrical conductivity of the water should be less than 0.5 mS/cm.
Pruning & Staking Tomatoes
The concentration of the nutrient solution must be adjusted at various stages throughout the growth cycle. The essential nutrients are divided into macro and micro elements. The macro elements (required at higher concentrations) are calcium, carbon, hydrogen, magnesium, nitrogen, oxygen, phosphorus, potassium, and sulfur. The micro elements are boron, chlorine, copper, iron, manganese, and molybdenum. Essential concentrations are measured in parts per million (ppm) or milligrams per liter (mg/L). Tomatoes require a relatively low nitrogen level compared to leaf crops and root crops. The required micro element levels for tomatoes are as follows: boron 0.44, chlorine 0.85, copper 0.05, iron 2.5, manganese 0.62, molybdenum 0.06, and zinc 0.09 ppm. The necessary concentration of macro elements changes after the plants reach about 24 inches tall and the fruit reaches about 1 to 1.5 cm in diameter. More nitrogen is needed in summer months or during times of higher light exposure, and more potassium is needed in the fall and winter months.

Nutrient Deficiencies

Nutrient deficiencies can cause a whole host of unwanted effects on the plants and adversely affect the crop’s fruit yield. pH levels that are too high result in hindered nutrient absorption. pH levels that are too low allow excessive absorption. Maintaining optimal lighting and temperature ranges create the best environment for healthy, high-yield plants. Some disorders may not show any visible signs right away or at all, so it is very important to ensure that your nutrient solution is properly maintained. Deficiencies can cause varying degrees of problems from delayed maturity, small fruit, curling and yellowed leaves to limited fruit yields and aborted flowers.

Lighting Requirements For Hydroponic Tomatoes
Light is the most important growth influencing factor. During the vegetative stage, plants produce a healthy supply of leafy vegetation that will later go on to feed and support the product yielded during their flowering stage. When starting a tomato seed, you can supply 24 hour light through to early vegetative stage. During the vegetative state, mature tomato plants thrive on 16 to 18 of direct light per day and eight hours of darkness for respiration.

LED grow lights are becoming increasingly popular to grow hydroponic tomatoes. They emit a powerful mixed spectrum of light that uses 1/3rd to 1/2 the energy compared to HID lighting. They also produce a minimal amount of heat, so they can safely be placed as close as within 30 cm of the plants. Plants respond more vigorously to the clean, cool, intense light emitted by LED grow lights, experiencing increased growth rates over HID so be sure to keep an eye on your nutrients.

Pruning and Staking Hydroponic Tomato Plants
Maintaining the architectural structure of the plants as they grow larger and begin to produce higher fruit yields keeps the plants strong and optimally feeding the fruit produced. You can use plastic twine to encourage a straight vertical growing path and to support the structure as it produces heavy fruit. Lateral side shoots and suckers should be removed. Gently break off suckers with your hands to avoid damaging or contaminating the plant. If the top of the plant dies, leave one strong lateral shoot to grow into the new leading shoot. Remove yellowed leaves at the main stem to avoid risk of disease and infection.

Patience and practice will ultimately lead you to a successful hydroponic tomato crop. Carefully balancing nutrients, aeration, pH levels, temperature, and lighting and misting schedules is a delicate process that takes some getting used to in order to get the greatest flavor, size, and quantity out of your produce. As you gain experience with recognizing potential issues and adjusting settings, you will no doubt learn to produce beautiful, delicious, vine ripened tomatoes year round.

Hope you enjoyed,

NPK