Hydroponic farms can be extremely efficient, but also easily disrupted. The key to a successful hydro operation is in maintaining the correct conditions of both water and air, while keeping a close eye on changes and fluctuations.

If you’re new to hydroponic farming, check out our introduction and pros and cons articles. In this installment of our series on hydroponics, we will discuss climate and water control- providing your plants with the right environment in order to thrive.

Overview of the Hydroponic Environment

The underlying principle of climate control, in any type of environmentally controlled agriculture, is about providing the crops with the optimal conditions to maximize quality and growth. The high-tech world of hydroponics follows the same path, and is in fact, an extension of this principle. In a soil-less setting, the plants gain easier access to the resources they need, at the price of increased susceptibility to any problem which may occur. This is, in a way, high stakes climate control. Greater crop potential, at a great risk.

What differs hydroponic growing from a traditional soil-based greenhouse is that, in addition to air climate control, there is an added emphasis on root conditions and the composition of the water which nourishes them, which fluctuates much easier than soil, and provides much less of a buffer between the roots and the environment.

The goal is to optimize the process of nutrient uptake, in other words, giving the plant what it desires in order to grow. In hydroponics, the optimal environment needs to be created completely artificially. The factors affecting this process are as such: the presence of nutrients and dissolved oxygen in the water, the acidity and temperature of the water, and the temperature and humidity of the air, which is in most cases, similar to non-hydroponic agricultural practices.

Providing Nutrients & Oxygen

Just as in any type of farming, to grow a good crop, you must provide the plants with nutrients, to break down and consume, as well as oxygen, to perform respiration, in other words- they need to eat and breathe.

In hydroponics, fertilization is done using liquid solutions containing different compositions. This allows for dynamic nutrient supply, which may be adjusted according to the type of crop, stage of growth and environmental conditions. Oxygen may be provided through several methods, the most common of which being either an air pump in the reservoir, or a “waterfall”, breaking the surface tension of the water to allow air to mix into it.

Nutrients are most commonly measured in EC – electric conductivity. This parameter measures the amount of salts in the water, which provides an estimation of the nutrient content.

The goal in hydroponic agriculture, when distilled into one simple guideline, is to create the best conditions to maximize the plants’ nutrient uptake. This is done through optimization of water and air conditions.

Water Temperature – Optimizing Uptake & Respiration While Reducing Disease

In nature, plants root into the earth, which in addition to providing the nutrients, also provides comfortable conditions. Therefore, roots have evolved to be more fragile and fussy than the rest of the plant.

The most basic parameter to keep an eye on is the temperature of the water. For most crops, it is commonly said the optimal temperature range is 18-24 Co (64-75 Fo). It is important to maintain a comfortable temperature for the roots to function effectively, but also to correctly manage the levels of dissolved oxygen.

The amount of dissolved oxygen which can potentially be contained in the water depends on the temperature. Colder water may hold more oxygen than warmer water, so one may conclude – the colder the better. But colder temperatures slow down the plants’ rate of growth. Too cold, and the growth will halt all together. On the other hand, if the water is too warm, the amount of dissolved oxygen may drop. This, in addition to providing less oxygen for the plants to breathe, which slows growth, may also prompt anaerobic pathogens to break out. The most common of which being Pythium, more commonly named “root rot”.

Water Temperature – Control Methods

Methods to maintain a fluctuation-free optimal temperature level include submersible heaters or water chillers, which may be automated, but may also require additional infrastructure such as dedicated pipes and pumps. The more DIY approach is adding frozen or boiling water bottles to the reservoir, though this may actually increase fluctuation if done improperly. It is also possible, in larger scale operations, to have the reservoir located in a control room, which allows for more precise control over the conditions, though this is most likely the most expensive of the many options available, and requires additional space and infrastructure.

Water Acidity – Preventing Nutrient Lockout

The acidity of the water is measured in pH, and has several effects. The acidity affects the solubility of the nutrients themselves. Meaning, each nutrient has a range of acidity in which it can be used by the plants. When the acidity levels wander out of the optimal range, the nutrients may become completely unavailable to the crops, creating what is known as “nutrient lockout”.

Each crop and each nutrient has its own optimal level of acidity, so it is impossible to define one go-to value. Though the optimal range is considered to be around 5.5 to 6.5, depending on the crop.

Adjusting the pH of the solution is done using pH buffers, either acids or bases manufactured for the purpose of lowering or raising the acidity level of the hydroponic solution. Additionally, like any material, fertilizers have a pH level, so adjusting the acidity after adding nutrients is always a good idea.

Nutrients in the Solution

The optimal level of EC differs wildly among crops and depends on the composition of the solution, the temperature of both water and air, humidity, lighting and the plant’s growth stage. So, aside from being the most important part of a hydroponic growing solution, it is also kind of a wild card, allowing it to be adjusted to compensate for different conditions.

It is important to note that excess nutrient salts may accumulate in the reservoir over time. These salts can bond together, thus becoming unavailable for plant consumption. This can be best noticed through common symptoms of nutrient deficiency, such as yellowing or burning of leaves. In order to avoid such situations, it is recommended to periodically clean the entire system.

Algae – The Weeds of Hydroponics

Hydroponic agriculture is considered to be weed-free, but that doesn’t mean you can sit back and relax.

Algae are an aquatic plant, which grows from spores. Like other pests and molds, its presence is inevitable. In small amounts, algae do not pose any threat, but when the colony grows, they may physically block pipes and pumps, becoming a big issue, which must be dealt with.

A bit of algae may actually be a good thing, as a plant, containing chlorophyll, algae photosynthesize, turning carbon into oxygen. This could be beneficial as a means of oxygen enrichment. It has also been found that some algae emit anti-fungal and anti-bacterial compounds.

The problems with algae, beyond blockage, begins when they bloom, die and decompose. The process of decomposing is the opposite of photosynthesis, instead of emitting oxygen, the algae begin consuming oxygen, becoming a major competitor for the dissolved oxygen meant for the plants. Additionally, when decomposing, many algae produce toxins which provide an organic source of nourishment for fungi, raising the likelihood of root rot taking place.

Controlling Algae Population

Completely preventing algae appearance is close to impossible, the real aim is to control the population. This can be done using a combination of several methods.

Like any plant, algae require a few basic conditions to exist: warmth, moisture, nutrients and light radiation. In order to prevent their appearance, they must be deprived of at least one of these. Due to the crops needing similar conditions, the temperature, moisture and nutrients can’t effectively be changed. The only remaining efficient method to prevent algae growth is by reducing, as much as possible, the amount of light penetrating the water. This is achieved by covering the reservoir and tightening the cover around the plants themselves, in DWC or NFT systems.

Additional actions to reduce algae include the use of filters and regularly cleaning the system, which should already part of the regiment, due to salt buildup. Some algaecides exist in the market, but being closely related to other plants, these may easily have a harmful effect on the plants’ roots and is definitely not recommended for intermediate growers. Additionally, massive algae die-off will cause a steep drop in the amount of dissolved oxygen in the solution. So, if facing large amounts of algae, it is better to clean and remove them physically, than kill them. Another method which is quite efficient is the use of hydrogen peroxide. When using a bit during routine cleaning and refilling, it is possible to get rid of the remaining algae spores. This should be done cautiously, as any remaining hydrogen peroxide will harm the roots as well.

Air Control

Controlling the climate of the air in the growing facility is the basis of greenhouse or indoor growing. Each crop has its own specific ranges in which it performs at maximum potential. The basic parameters to look out for are temperatures and relative humidity.

Temperature

Though these are unrelated to hydroponics, the fact that the water provides less of a buffer than soil, means that these parameters need to be kept in a tighter range and fluctuations may be much more devastating. For example, if the temperature drops, the temperature of the water will drop much quicker than soil would, making it very susceptible.

Humidity

Relative humidity has two critical affects. The first being the rate of nutrient transfer. If relative humidity is too high, the plant will transpire less water, and in turn, take in less water from the roots. This slows down the rate of nutrient uptake, which is the critical factor in maximizing plant potential.

Additionally, high levels of relative humidity create the risk of condensation, the appearance of free water. This water could become a hot bed for disease such as botrytis or downy mildew, which have the potential to decimate crops.

More on the effects of humidity can be found here.

Air Circulation

Creating the right circulation of air in the growing space helps by creating uniformity, and essentially glues together the efforts to maintain the correct climate. By unifying the conditions, it is easier to avoid fluctuations between different areas, maintaining a consistent crop quality, and avoiding disease outbreak, which could potentially travel through the space, infecting crops that would otherwise be in safe conditions.

More on the benefits of air circulation can be found here.

High Risk, High Reward

Hydroponic growing can be done using different methods, all of which have their own strengths and weaknesses, but all share one commonality – they require very close attention.

This technique creates a system which renders the plants much more vulnerable, and the end result of sub-optimal conditions may be devastating in comparison to traditional greenhouse growing. Though when done correctly, these methods have the potential to greatly outperform the techniques in which mankind has been growing food for millennia.