How to grow hemp hydroponically

Hydroponics is a method of growing plants in a water-based, nutrient-rich solution. With the push for more economical, environmentally friendly, and sustainable practices of growing crops, hydroponics has become a method of plant cultivation popular among growers from a range of different backgrounds including both domestic and commercial. The basic concept behind hydroponics is the suspension of plant roots in water so that the roots come into direct contact with a solution high in nutrients while also being exposed to sufficient levels of oxygen. This exact environment is essential for plant growth.

With the projected increase in the demand for hemp products, commercial greenhouse operators should be aware of efficient methods of yield production of this crop. Hydroponics is a method that could vastly improve yields allowing producers to meet the ever increasing demand for hemp.

Why hydroponics?
There are many advantages in growing hydroponically. The greatest advantage is the substantial increase of growth rate for plants. When a hydroponic system is run correctly, plants can grow up to 25% faster and have up to 30% more growth when compared with conventional growing techniques using soil. Plants grown in water do not have to fight to find nutrients like they do in soil. With hydroponics, it is possible to carefully control various aspects such as the correct nutrient and pH levels allowing plant growth to increase and yields substantial. Although a hydroponic system uses water, a system actually uses less water than soil based plants due to it being enclosed. This leads to less evaporation of water. Not only is it water conscious to grow hydroponically, is also better for the environment due to reduction of waste and pollution from runoff.

Hemp and Hydroponics
In the industrial hemp farming industry, growers have embraced hydroponics in order to meet demand for product instead of using traditional growing practices to grow industrial hemp. Growers are making the switch to hydroponics. With moving plants indoors it is essential to understand the needs of hemp plants throughout the growth cycle especially when using a hydroponic system. Consideration must be taken for the medium used to house roots for plants grown in water, temperature requirements, nutrients, lighting, and other key factors that influence the way a grower must grow hemp indoors.

In the production of hemp, hydroponic cultivation generally occurs in a greenhouse or indoors. For these systems there are many different types ranging from ebb and flow, drip systems, aeroponic systems, and aquaponic systems. Since hydroponic systems increase aeration of plant roots, and control of nutrient uptake, growers find it very beneficial for growing their plants in water instead of soil. Although these plants are grown in water, growers use soilless media to aid in nutrient retention and support for plants. Many growers use coconut fiber, such as Ricocco, due to its high drainage and buffering capabilities that make it virtually impossible to apply too much fertilizer. If the system were to shut down, the coconut coir will allow a crop to maintain moisture lessening the chance of crop loss for a longer period of time in comparison to a system without the coir.

Types of Commercial Hydroponic Growing Systems for Hemp
In the world of hydroponics, there are several different systems that a grower can use. These are wick systems, deep water culture (DWC), nutrient film technique (NFT), ebb and flow, aeroponics, and drip systems. Each system has its benefits and drawbacks. The choice of system sole depends on the greenhouse’s needs and crop needs.

In a wicking system, the water and nutrient solution is fed into the root zone through a wick or rope. When the area dries, the water and nutrients feed up through the rope into the areas water is needed. A wicking system is not suitable for larger plants and may not be suitable for hemp production when plants are more mature than a seedling.

In a DWC system, the plants are housed in a large reservoir filled with water and nutrient solution. The installation of an air pump allows the water to be oxygenated to allow the roots to breathe. Plants in this system are housed in a net to allow the plants to have support in the deep water. Although the water is deeper than a standard hydroponic system, this is not suitable for larger plants.

The NFT uses the concept similar to the DWS, however, the difference is that the plants are suspended in a smaller trough over the reservoir. A pump brings the water up to the trough and through a slight slant, the water drops back into the reservoir. Larger plants can be grown in this system, though a grower must watch for tangling of the roots as well as clogging in the system.

An ebb and flow system the roots are not exposed to nutrient solution and water constantly. The grow trays are filled with medium and “flooded” with nutrient solution throughout the day depending on plant needs. Water is stored in a reservoir below the tray with the plants and is pumped through them. The flexibility and water efficiency makes it a top choice for growers. Close attention should be given to root health as roots could dry out quickly if the system stops working.

Aeroponics is similar to the NFT system due to the roots being suspended in air. The difference is that the system uses a mist system on roots continuously instead of flooding. This system has shown in studies to grow plants quicker. Roots are exposed to more oxygen than submerged systems. A grower needs to monitor nozzles to avoid extended drying of roots to prevent root death in plants.

Drip systems are the most common among commercial greenhouse operators due to its simple operation on a large scale. Similar to the other systems, this uses a reservoir and a pump to deliver water to grow trays. The hose then has sections diverting water to the individual pots. This system is relatively cheap, less likely to break, and has high control over the schedules for feeding and watering. Due to fluctuating pH and plant nutrient levels, monitoring is essential to guarantee maximum efficiency of the system.

Setting Up A Hydroponic System for Hemp  
To ensure proper growth and maximize yields, is it important for growers to set up their hydroponic system correctly. By doing this, a grower ensures that their plants are getting all the needed nutrients a plant requires to lead a healthy, happy life. Growing hemp hydroponically differs from that of a traditional hydroponics system such as one that is used for lettuce production. This is instead similar to the method tomatoes are grown within a hydroponic system.

The plants are placed in a large hydroponic container around 40 liters. In this container, a grower must place ion exchanger, Hydro granules, rockwool slabs, and a water level indicator. Generally speaking, 100 CCs of an ion exchanger on the bottom combined with a layer of hydro granules is sufficient for the hydropot.

After placing these at the bottom, rockwool slabs should be inserted after soaking. then adding another layer of hydro granules to the top will be sufficient for placing plants. The reason for placing hydro granules is to ensure a climate that is perfect for roots. This climate must be aerated and have ensured moisture. An ion exchanger should be used to prevent the nutrient solution running through the containers from getting too acidic. This is because ion exchanger binds elements that cause the increase the acidity meaning that nutrients can then be released. A water level indicator is also essential to ensure that a container has the correct amount of nutrient solution running through it.

Indoor Hemp Production Requirements
Just like with any crop grown indoors, certain environmental factors must be controlled and supplemented. After the production system is installed and the plants are in place, a grower must maintain water, nutrients, lighting, and air quality. The benefit of growing in a greenhouse is that the crops can be grown much quicker than conventional methods. A greenhouse gives the opportunity to allow a grower to provide endless hours of light, increased CO2 levels, and controlled humidity.

Commercial Grow Light Supply for Indoor Hemp Farmers
A grower must be aware of the individual light needs of their crop and should consult with manufacturer specifications for lights and plants. Additionally, the room’s size and ventilation must be considered. Hemp plants require very specific lighting due to being photo-sensitive. Hemp needs periods of dark and light in specific intervals for optimal growth. The lighting system must therefore have a timer installed to make light control easier for the grower. The optimum photo-period depends on the specific plant variety and should be researched before growing.

There have been advancements with LED technology to allow the light diodes to emit enough energy for hemp production. Diodes emit light in specific ranges and allow for total control over the spectrums of light present for the plants. Commercial LED plant lights, thanks to advancements, are able to produce all the light in the PAR spectrum (photosynthetically active range). In order to increase the efficiency of the LED lights, grower will often install reflectors. These reflectors reflect the light given off by the LED’s to increase the amount of light in a growing space. In order to keep efficiency high for lighting, a grower should move plants and/ or lights as close as possible to the plants so that the crop can receive equal lighting and all light emitted hits the plants’ leaves.

To get the ultimate efficiency in a greenhouse, installing a concave canopy with the periphery and center of the canopy at the correct distances can provide optimum light sources for the hemp crop. It is important that the plants do not actually touch the lamps as this will scorch the plants.

  • Lamp Type
  • Recommended Distance from Plants
  • Pressure Sodium Lamps
  • 2 feet (0.6m)
  • Large, Compact Fluorescent Lamps
  • 4 inches (10 cm) 

With proper ventilation and cooling, any of the light sources can be moved closer to combat what is known as the inverse square law. However, closer lights that are placed too close to plants can cause bleaching of the plant material. Decreasing distance between lamps and plants also reduces the overall coverage of the canopy. 

Control of the Atmosphere
The grower must be aware of the hemp crop’s atmospheric needs and strive to provide the ideal atmosphere inside the greenhouse or CEA facility. The overall air temperature should be maintained within a specific range no greater than 18 degrees Fahrenheit with cooler nights and warmer days. These levels can be maintained and tracked easily through digital thermostats installed in the grow area.  CO2 levels should be maintained at the desired levels at all times to ensure adequate plant growth. Ventilation is also essential in a grow area so that temperature and CO2 levels are maintained.

Growing Media for Hydroponics
When someone thinks of hydroponics, often they will think that all that is needed is water for the plants to grow in. However, growers will implement soilless grow media to promote root growth to properly support the weight and growth. There are many different types of media used in a media-based hydronic system. Each media has its benefits. In the systems the media is placed in either grow trays, grow beds, troughs, or grow containers. This area is irrigated for the nutrient solution to run through. For the media to be the most effective it must be inert and resistant to mold growth. Weight of the media must be so that it does not float in the water, but not heavy to bog roots down. Due to the media being inert, it provides no nutrients to the plants. It is simply used as a support system for plants to grow. Some of the most popular soilless media used in hydroponics is rock wool, expanded clay aggregate, coco coir, and perlite. Gravel has also been seen in some hydroponics with varying degrees of success. Each of these media types offer unique benefits for a hydroponic system.

Coco coir is an excellent growing media for hemp plants. Careful care of pH is essential in a system that uses coco coir, as well as monitoring of calcium and magnesium. The pH levels should not be lower than 5.5 and no higher than 6.5 for optimum hemp growth. When using coco coir, a grower should also implement a Calcium- Magnesium supplement to balance the needed nutrients.

Rockwool is the most popular of soilless growing media Rockwool provides excellent moisture control and aeration of the roots. This man-made material is a convenient option for a grower as it is easily adjustable in size and resists degradation within the system. This prevents clogging of the hydroponics system. Due to the general alkalinity of rockwool, pH levels should be monitored to ensure the pH doesn’t rise to a level that affects the plant’s health and growth.

Perlite is another option of the hydroponics grower. This material is inert, porous, and lightweight meaning that it has excellent water retention and drainage. This material is naturally sterile helping to reduce contamination and mold growth. The pH of perlite is neutral, however, it will take on the pH of the nutrient solution running through the hydroponic system. If the pH becomes unbalanced, perlite can be removed and rinsed to reset the level to a neutral 7. Additionally, perlite acts as a natural root insulator for plants.

Vermiculite is another popular media used in hydroponic systems. This material is very similar to perlite having light weight and sterile properties. This material has great water retention and capillary action allowing it to be fully hydrated from applying moisture from either above or below. Vermiculite is sometimes combined with perlite if it starts to become water-logged. Hydroponic growers do this to improve aeration and decreases compaction.

Nutrient Mixes for Every Stage of the Hemp Growing Process
Throughout the life cycle of hemp, the plants need certain nutrients to maximize growth and reduce stress in plants. Hemp is known for its high nutrient uptake. According to the Canadian Fertilizer Institute hemp requires 200 kg of Nitrogen, 47 kg of Phosphorus, 211 kg of potassium, and 14 kg of sulfur per hectare. On average, hemp will consume or uptake 6.7 kg of Nitrogen, 1.56 kg of Phosphorus, and 6 kg of potassium per hectare. This high uptake is very similar to that of canola. A grower must monitor the nutrients in the solution closely to meet the high demand of hemp during the growth cycle.

Pest Control in Hemp Production
Although hemp is regarded as a crop that is pest and disease resistant, the crop can fall to some pests and diseases. Pest and disease control can be done safely and easily. Some common types of pests are nematodes, borers, flies, and fleas. Diseases that can strike a hemp crop are mold, rust, and cankers. These can be controlled through best practices and the applications of pesticide, herbicide, or fungicide when needed.

For more information:
RF Agriculture
622 North La Brea Avenue
Inglewood, CA 90302 
T: (310) 967-2022 
F: (310) 967-2024   

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