Ask the Professor – Prev. Questions 7

Professor –

I have just gotten started with a home built hydroponic system and so far have been having excellent results.

I have been noticing that the leaves on all my plants (vegetables.. squash, beans,tomatoes) are very soft and at times downright limp. What is up with that? I’m using white 4gal buckets, could there be too much light coming thru?


Greg –

I don’t think that light getting into the root zone is the problem, I have used 5 gallon buckets for years and not had a problem. It sounds like the plants are drying out. What growing medium are you using? Are you hand watering? If so, how much / how often?


Professor –

I’m a fifth grader working on a science fair project about the effect of 24 hour light on plants. I need to know what is the best and least expensive way to light my plants. I will be growing small plants (probably marigolds) in an aquarium sized area. What should I use?


Melissa –

The best way to light your garden would be to use HID (high intensity discharge) light, Metal Halide (MH) or High Pressure Sodium (HPS).

However this type of lighting is rather expensive. Probably the most cost effective lighting for your project would be to use fluorescent lights. The fluorescent light doesn’t penetrate very far so the lights should be kept very close to the top of your plants (1 – 2 inches). CLICK HERE for a link to a good article about lighting.


Professor –

Is one bean better-suited to hydroponics than another? If so, what is it, how long will it take to grow, and where can I get the seeds?


H. –

I have really never heard of any particular type of bean that does better hydroponically than others. Most any type of bean should do very well hydroponically.


Professor –

Is it possible to break down animal manure with enzymes, so that it could be used as sole nutrient in a hydroponic system?


Jan –

Making your own nutrients is very tricky but it can be done. You can soak the manure or other organic materials in a container of water and keep the mixture (often called “tea”) well aerated. After a period of time, usually a week or so, you strain the mixture and use the liquid to feed the plants. This process may sound simple, however, getting everything right is hard. There is a lot of trial and error involved. You need to get a balanced and consistent mix. Also, animal manure alone will not supply all the nutrient requirements. Things like kelp, seaweed, bird/bat guano, etc…. need to be used with the animal manure to produce a complete balanced nutrient.


Professor –

What does a beginner need to know (and complete set up list) about their first hydroponic garden?


Anissa –

There are several things that a beginner needs to know about hydroponics. Growing mediums, nutrients and pH are the three biggest. Hydroponics can seem pretty intimidating at first, but once you have a little basic knowledge it is really quite simple. We tell people to read what ever they can about hydroponics and then ask specific questions.


Professor –

Do you think that hydroponic growth will eventually replace field growth of produce? Also, What pro’s and cons are there?


Ira –

Hydroponics has already replaced much of the dirt farming in many areas of the world where there isn’t enough good farm land, or where the weather doesn’t allow for good growth. New Zealand and Australia grow extensively using hydroponics, mainly due to poor rocky soil. The middle east grows most everything hydroponically due to the fact that a great deal of the land is desert. Canada grows a very large percentage of it’s crops hydroponically due to it’s very short growing season. In fact the country that is growing the least amount of produce hydroponically is the United States. With the abundance of once fertile farming land and mild climate there isn’t a need for extensive hydroponic farming…….yet. However years of crop production an the same land is causing problems. The soil is building up salts from irrigation and fertilization and a great deal of the now highly productive farm land will become unsuitable for crop production in the future. Another major problem caused by conventional farming is pollution. A percentage of the fertilizer runs off due to rain and ends up in streams, rivers, lakes and eventually the oceans which can cause problems with algae blooms and fish kills and the like. Another problem associated with conventional farming is the lack of good quality water. With the huge population explosion of humans on this planet, good quality drinking water is getting harder and harder to find and putting millions of gallons of water on crops is only compounding the problem.

The major advantages of hydroponics is: 1 – There is a drastic increase ofthe amount of food per acre (200% to 300 %) with hydroponics over dirt farming. 2 – Hydroponics uses only 10% of the water used by dirt farming. 3 – There is no fertilizer run off when using hydroponics. 4 – The produce from hydroponic gardening is usually healthier than that of dirt gardening, because the plant receives a completely balanced nutrient formula including the essential “Micro-nutrients” that are not present is normal “dirt” fertilizers. Plants grown in dirt are expected to get these micro-nutrients from the soil, which is great if the elements are actually present is the soil, but all to often these essential elements are depleted from the soil due to excessive farming or they were never present in the soil to begin with. The major drawback to hydroponic farming is the initial set-up cost. It can be rather expensive to set up a large hydroponic system. The cost is usually recovered very quickly once the system is up and running. There is a great deal of hydroponic gardening in the United States now and I would expect that this percentage will continue to grow, I doubt that it will ever totally replace dirt farming but hydroponics will certainly get more and more popular for wholesale crop production.


Professor –

I’m doing a science fair project on Hydroponics, and I was wondering if I should germinate the lettuce seeds first, or if there’s a way to do it with less hidden variables hydroponically. My teacher said that I need to find out if it is possible to have the seeds grow hydroponically, using the water culture system, because germinating them in soil would have too many hidden variables & might throw off my conclusion. – Katie


Katie –

If you don’t have “starter cubes” you can start your seeds in a bit of paper towel, or a piece of foam rubber or other similar material. After the seeds sprout you can transfer them to the water culture system. Just make sure that the material that you are using doesn’t dry out. You want the seed starting material to be kept damp but not wet. The paper towel (or foam or whatever you use) contains no nutrients to throw off your results.


Professor –

I am a glassblower using 2 oxygen generators. I don’t get as much use as I could out of them (they are made to run for tens of thousands of hours without servicing). I am wondering if there would be any significant difference using the 95% oxygen from these generators instead of ambient air to oxyginate my water reservior. Granted, these generators cost practically nothing to run (in use-depreciation or electricity), but I’d hate to waste my time and generator’s life-span if there is no point.



You’d think that after 20 years or so in the business fielding questions from all corners that I’d have most if not all the answers, but every so often I get a question that humbles me back to reality and all I can say is: “damned if I know”. Well………………..Damned if I know. I’ve asked almost everyone that I can think of and what I came up with was a group “damned if we know”. I haven’t asked everyone yet, and I will keep digging to try and find your answer. I will update you with what I find out.

There are many commercial hydroponic growers that inject oxygen to the upper root zone of the plants. This is shown to benefit growth as a plants upper root zone is designed to uptake oxygen. These type of systems are usually N.F.T. systems that separate the root zone from the upper plant zone, usually with plastic. This enables oxygen injection without diluting the CO2 that is required in the plants upper zone (the green side). Many growers will inject oxygen to the roots and CO2 to the leaves.

As far as aerating the reservoir. I know that water has a limit as to how much oxygen it can hold. Usually around 18% is the best you can hope for but this depends on temperature (the warmer the water the less oxygen it can hold). I don’t know if aerating with pure oxygen would increase this percentage or not. I have my doubts. There are a few things that will temporarily raise oxygen levels, like adding hydrogen peroxide to the water. I have seen people use an I.V. type drip to steadily drip hydrogen peroxide into the reservoir to increase Oxygen levels. This method is kind of expensive, the hydrogen peroxide dilutes the nutrient solution and quite frankly it’s a pain in the butt.

Do you have a method of doing a side-by-side comparison? That would be the best way to determine if there is any benefit. I would greatly appreciate any data you develop if you decide to try this test.