Have you ever wondered why you can’t seem to find a great tasting tomato out of season? One of the reasons is that most hot-house tomatoes are picked when the fruit has barely started to ripen. Then they are packed, shipped thousands of miles in storage containers, and then artificially ripened with ethylene gas to turn them red. No wonder the tomatoes are so tasteless! Even a tomato labeled “vine ripened” doesn’t mean that much. For example, in Canada “vine ripened” simply means that there is at least a streak of yellow in the fruit when it is harvested, and most of the tomatoes are harvested just at the breaker stage (starting to turn pink). That way, they are easier to ship.

On the other hand, I’ve grown hydroponic tomatoes in my basement for years, and they taste like they came out of the garden in August! In a 3’ X 3’ space with a 600-watt lamp, I can harvest literally thousands of cherry tomatoes over the winter, ripe on the vine. In fact, my home-grown hydroponic tomatoes are so packed with sugars and vitamins that I can pick a perfectly ripe tomato, set in on the table, and it won’t start going bad for at least two weeks! I never put a tomato in the refrigerator.

There are two tricks to growing sweeter tomatoes: raising the EC, and keeping the potassium to nitrogen ratio high. EC stands for electrical conductivity. Distilled water doesn’t conduct electricity; it has an EC of about zero. But the higher the mineral concentration in the water, the more it conducts electricity and the higher the EC. There is a directly-proportional relationship between EC and sugar content in the fruit. Higher EC equals more sugar. When you raise the EC by adding more minerals, the nutrient solution becomes “saltier”, and the roots have more difficulty taking up water. So the sugars, organic acids and vitamins actually condense and accumulate in the fruit. In fact, if you raise the EC high enough, you can actually double the lycopene content (red pigment) of tomatoes so they are red all the way through! The fruits might be a little smaller, but they are densely packed with nutrients and flavor.
The next trick is raising the potassium to nitrate ratio of the nutrient solution. Potassium is a catalyst for carbohydrate metabolism in the plant, while nitrate-nitrogen depletes sugars in favor of vegetative growth. So to grow sweeter tomatoes, make sure the potassium: nitrate ratio is at least two to one. Even then, during heavy fruiting and flowering the plants could significantly draw down the potassium levels in the nutrient solution and create a potassium deficiency. If tomatoes experience a potassium deficiency, the fruit will be watery, with low sugar content and poor shelf life. So during the generative stage, I like to top off the reservoir with a potassium boost every time I add water between reservoir changes. Keeping the potassium levels high ensures that I keep growing the best of the best!
Water-soluble potassium sulfate makes a great boost formula for growing sweeter tomatoes. Just make sure to use a clean, high-quality potassium supplement with a fine particle size (<0.015 mm). Fine particles dissolve more rapidly, and they are better suited for irrigation or foliar sprays. Potassium sulfate will also help raise the EC without adding additional nitrate-nitrogen! When raising EC, how high is too high? That depends on the plant and the environmental conditions. If the leaves start to curl a little, that’s usually okay, but if the leaves start to curl and turn brown at the edges, that’s too high. Stress is good, but too much stress will put you in the hospital! Gradually raise your EC with potassium supplements until you find the perfect dose for the sweetest fruit.
Copyright© 2013
Harley Smith

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