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Hydroponics pros and cons

Hydroponics pros and cons explained at Mean Green Magazine

Advantages: Why Hydro?

You might very well ask yourself: Why bother to spend money on hydroponics systems, when you can just put a plant in a pot with soil and grow it with no major investment, right?

In fact, I think this reasoning is incorrect. There are many of reasons to use hydroponics technologies.
Let’s have a look at what hydro can do, first on a larger, worldly scale and then in your own growroom.

Control of nutrition

The first benefit – and it is of utmost importance – is that you completely control the nutrition of your plant. Only the elements that you put in the water will be present in the root zone, in the proportions that you choose. You can control the quality as well as the quantity of the nutrients dissolved in the water at all times. Remember that it is thanks to hydroponic technologies that plant science has advanced over the past 200 years, in particular in the field of plant nutrition. Today, most research around plants involves hydroponics. As controversial as it might be, it is also used for research in genetics and gene transfer.

Conservation of water

Don’t get this wrong. A plant needs to transpire a certain quantity of water to sustain healthy grow. The fast, lush growth happening in hydroponics will mean significant water consumption. However, all the water used will be transpired by the plant. None is wasted in the soil or by evaporation. The savings in water as compared to similar plants grown in soil is quite dramatic. Recent improvements in irrigation practices, from spraying a whole field to delivering water at the base of the plant, has significantly improved water consumption in horticulture. However, hydroponics is still many times more efficient in this regard.

Conservation of nutrient

By the same token, all the nutrient used is absorbed by the plant. None is lost into the ground, therefore avoiding the danger of ground water pollution and microbial life in the soil is not impacted.

Better health and faster growth reduces the need for pesticides

The word pesticide by itself is a misnomer. These substances should be called biocides, since they kill anything alive (but who would buy a biocide!) Many people mistakenly believe that pesticides kill only pests. In fact, they are not selective and also kill beneficial organisms. Their use should be restricted to the rare exception. A plant in hydro, if well tended, will grow fast and healthy, allowing that plant to outgrow the pest, or be strong enough to resist it. This does not mean that you will never need pest control with hydro, but rather that the need will be reduced and you can cure problems with gentler solutions than killing everything alive at the perimeters of your plants. This, of course, is most true for fast growing annuals. It is more debatable for perennials, even though the strong vigor exhibited by hydroponically grown plants helps also in that case.

No need for herbicide

This one is rather obvious. In those plastic trays or plastic channels, there is no room for weeds to grow. Both the facts that herbicide is not needed, and that pests can be killed gently, makes hydroponics a very clean technology.

A plant started in hydroponics is vigorous

If you keep a mother plant in hydro to then clone it and transplant the babies outside in soil, they will grow more vigorously than if they come from a mother in soil. I have performed that experiment myself many times and the difference is always dramatic.

Optimum utilization of plant genetic potentials

A classic image of a growing operation is a chain, which is only as strong as its weakest link. What this means in cultivation is that there will always be a limiting factor. It could be light, carbon dioxide (CO2), humidity, nutritional deficiency, or whatever. When growing hydroponically, you remove most of the weak links in the chain, especially everything related to element blockage in soil, which happens often for many reasons. The plant now has optimal conditions to express its full potential. Genetics might become the weak link, if you did not choose your variety wisely. Over the years we grew in our greenhouse huge plants never seen in nature; it is not that we do anything special, we just reinforce weak links. In your grow room, you can often put your plants in ideal situations in terms of nutrition, light level, temperature, and humidity. Your weak link will then be carbon dioxide.

Increase both size and quality of crops

It is obvious that if you improve the overall health of the plant, you will also increase the output, the harvest. Hydroponically grown produce is noticeably larger than soil-grown. Suddenly, a cherry tomato does not look like a cherry any more. Also, on the nutritional front, analyses of hydroponically grown produce systematically demonstrate a large increase, often double, in the quantities of both vitamins and mineral salts content. This also holds true for active principles in medicinal plants.

Access to the roots

It is very practical to check the health of your roots at all times. With hydro, plant roots are not buried in soil, which makes it much more convenient to check on root health. Frequent checking for possible pathogens allows early detection; early treatment increases effectiveness. Root inspection will also tell you a lot about your plant’s health and how it will develop in the future.

In most hydro systems, one has easy access to the roots. With experience, you can discard those cuttings that are alive, grow healthy roots… but don’t have a nice implantation around the stem. I have grown so used to it that it is weird for me to grow a plant without looking at its roots. Using a hydro setup is especially beneficial when cultivating a crop where the root is the main product. In most medicinal plants, the active principles are located (or are also) in the roots. In some cases, the ones in the roots differ from those in the aerial part of the plant. It is impossible to extract them without destroying the plant.

As a result, many medicinals are over-harvested in nature, sometimes to the point of extinction. In some closed hydroponics systems, the roots are bare and soak in a flow of nutrient. In this situation, you can harvest a large quantity of the roots on an almost continuous basis without destroying the plants. Obviously, you have to cut some of the aerial parts at the same time to keep the plant in good balance. In some cases, this green biomass is by itself another source of extraction, other times it is simply composted.

Harvesting roots in this manner keep them clean, not requiring a wash or any other process before extraction. They are also very rich in active principles, but concentration can be increased even further by adapting the plant nutrition to the type of molecule that one wishes to produce. Furthermore, we can increase the growth of the roots themselves by controlling the level of dissolved oxygen in the nutrient solution.

In this field, as in all the others when it comes to cultivation, it is necessary to secure a market, and organize the commercialization of the product before starting the cultivation. However, in this case, it is less critical than with fruits or vegetables, since the dry roots can be kept for a long time with no damage. This opens new horizons to the greenhouse industry, an endangered one.

Production of a large quantity of biomass

Hydroponics does that. The high level of nitrate in the nutrient solution allows the plant to explode its vegetative growth. That is an advantage when a large mass of green is needed. Hydroponic basins could be used to clean heavily polluted waters. The by-product would be a large green mass that could be converted into fuel. The technology exists and numerous successful experiments have been conducted. In one remarkable instance in Portugal, a research institute managed to clean the effluents from a pig farm, and those are as bad as you can get. They turned them into a profitable crop. Why this method is not used more widely is a puzzle to me.

Better use of space

The root mat does not have to extend so much as it does in soil. The plants can get all the nutrition they need in a restricted space, without competition between them to speak of. As a result, plants can be grown much closer to each other than they can in soil. This allows practices such as the “sea of green”, in which the plant density is incredible: it can reach 60/70 plants per square meter. Without going to that extreme, we will see later in this book that under lights it is better to grow many small plants than a few big ones: hydroponics is extremely suited for this technique.

No soil to carry up and down

This, for me, is a big advantage. In fact, I first came to hydro just for that. In the 80s when I first decided that I wanted to have a grow room, I could not stand the idea of carrying all those heavy bags back and forth. It is not much of a concern when you live in a house, but when you are in an apartment, carrying large quantities of bags full of soil is not very practical. It can even turn into a real pain. Hydro generates little refuse, and there is not much to be replaced between each crop. That makes it a perfect technology for small, confined spaces. I started out with water-culture technologies thanks to a certain laziness, and I’ve never stopped since then. I have never regretted that choice and nothing would make me put my plants back into earth. I rather work on ways of incorporating the benefits of earth into water.

Control of nutrition

I list it here again because it takes another meaning in this context. Unlike plants such as tomatoes or peppers, and many others growing and reproducing at the same time, there is a group of plants with a marked vegetative stage followed by a marked flowering and fruiting stage. For these plants, the two stages require utterly different nutrition. This can be accomplished in soil, at the expense of a certain waste, by flushing repeatedly with water. In hydro, this is only “empty the tank, fill up the tank”. The leftover vegetative solution does not have to be discarded. It goes on your house or garden plants, not down the drain. I think that that drastic change in the composition of the nutrient solution is one of the reasons why the flowering and fruiting go faster: The plants get a strong signal that it is time to flower, and at the same time they are provided with all the elements that they need to do it. After all those years of growing hydroponically, I am still amazed how a minute change in the equilibrium of the nutrient solution results in a large difference in plant growth. It can be plant morphology, or taste and nutritional value of the crop. Apparently, the composition in salts of the nutrient solution is the main factor that will influence the final product.

Accelerated growth of a mother plant

A plant grown hydroponically with a nutrition rich in nitrogen will grow lush green vegetation. For some people, it is even too much, but if you need to produce a large quantity of cuttings continuously, there is nothing like a mother plant in an efficient hydroponics system. This fact is widely used in the horticulture industry to propagate many species of plants in large quantities. Again, those clones can be grown in hydroponics but also in soil, where they will have the famous cutting vigor… but with an extra edge. This is too good to be true, you say, and yes, there are some disadvantages.


The first and most important disadvantage is that the plants are not protected from your mistakes. Soil has a buffering capacity, which provides a certain stability around the root mat. In healthy soil, all the physical and biological parameters are in balance. If you give your plants too much nutrient, a wrong mix, or something with the pH completely off, the micro-organisms in the top soil as well as the soil chemistry itself will tend to reestablish equilibrium. This happens also in hydro, but only to a limited extent. The nutrient solution has some buffering capacity, especially in terms of pH, but nothing comparable with soil. Something as trivial as a pH meter off scale can have dire consequences, such as killing your entire crop in a day.

Things happen fast in hydro

An image that I like to use is the comparison between driving a race car and driving your family car. At the wheel of a race car, you go much faster, but an accident is likely to have much worse consequences. Growing in hydro is the same. It goes so fast that you can literally see the plants grow… but you can kill them in one hour. Temperature is also a limitation. 18°C to 22°C in the root zone is the range at which plants grow best in hydro. They can tolerate much more. Up to about 26°C nothing happens, then growth slows down, and at around 35°C their roots, lacking dissolved oxygen, start dying fast, and so do the plants.

There are means of fighting the heat that we will see later ; nonetheless, it is a severe limitation, especially in tropical countries and indoors, where artificial lights generate a lot of heat. Another limitation is that you cannot grow every crop in hydroponics. All the roots or tuber crops, such as carrots or potatoes; everything that is harvested from inside the ground, require very special systems. The economics of a crop are also a limitation. For instance, wheat would grow well in hydro but this would not be economically feasible. The geographical location, as well as the local market, will determine which crop is feasible to grow and which is not.

There are other criticisms I often hear when I talk with people on the subject of hydro. The two main ones are that it is expensive to initiate, and it is unnatural. I even have heard the expression “plants on a drip”, used in its medical sense. It is true that hydroponics systems have a cost that can be steep, but in indoor cultivation you rapidly recover the money you spent. The reason is simple: electricity is expensive. When you grow plants under lights, you want to harvest your crop as fast as possible because the total usage of electricity, between the lights and climate control, is significant, even for the smallest growing operation.

The faster you get your harvest, the lower your production costs

Hydroponics saves time, and a lot of it. In this case time is really money. As for unnatural, I find this also debatable. After all, what is natural? Is planting an entire field with a single plant “natural”? Nature is diversity. Think about it; by definition all forms of agricultures are “unnatural” practices, strange as that may sound. When humans were still at the hunter/gatherer stage, our impact on the planet was nearly nil. Like all other living organisms, we would take our food from our environment, but we did not modify it very much most of the time. The problem started when we passed on to the agricultural stage, when we started to plant crops in fields. This allowed man to change from a nomadic life to a sedentary one. Soon the villages became cities, then cities-states, fighting with each other for more land, and that led to the civilization that is ours today.

All of today’s problems can be traced back to the first man who planted a field.

Hydroponics with its plastic tubes and mineral salts might seem weird at first sight, but at the end of the day, it is no more or less unnatural than agriculture itself. Strangely, people don’t seem to mind using mineral salts to feed their house plants in soil. They do it recklessly, with the risk of nutrients ending up in ground water or the city sewer. Conversely, they seem to mind using those same mineral salts, in an even purer form, in the safety of a plastic gutter.

They would resort to foliar feeding, not very common in nature you must admit, but they see roots bathing in a nutrient solution as unnatural. There are many islands where the land cannot feed the large tourist population, tropical countries where the soil is full of hungry pests, places where the land has been so abused that it has lost most of its fertility, places with no arable land at all.

Everywhere that organic cultivation cannot be the only option, hydroponics could be one of the solutions to feed a hungry world without destroying our environment. It is a type of agriculture that can provide man with nutritious and delicious produce as well as medicines in places where it would be impossible otherwise. Its level of “unnaturalness” is irrelevant.

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