Cannabis Irrigation Technology for Each Growing Method

There are a few mainstays within the cannabis industry when discussing cultivation methods. Organic, hydroponic, greenhouse, aquaponic, and aeroponic; the list also includes many variations and hybrid methodologies.

Location or cultivation methods do not change the basic needs of the cannabis plant. Providing plenty of light, water, and nutrients, combined with optimal temperatures and humidity levels, should provide a bountiful harvest. The differences come down to the delivery of these needs.

Environmental variables create deviations from one grow recipe to another; lights, temperature, and humidity levels need to be within a specific range to succeed when growing cannabis. Thanks to years of ag tech advancements, HVAC systems, LED light programming, dehumidifiers, irrigation, and fertigation, can be completely customized and scaled to the size and type of cannabis operation.

This article will focus on indoor cannabis cultivation using soil, hydroponic, and aquaponic methods and the differences in irrigation and fertigation.

Irrigation technology from the watering can to fully automated

Irrigation/fertigation choices range from the most primitive, non-electric, manually performed applications to fully automated systems with all the bells and whistles. 

Basic systems require hand mixing a measured amount of nutrients and water, then applying them directly to the plants by hand. Some utilize low-cost pressure injectors automatically pumping water and nutrients into table solenoids via a drip system controlled by clock timers.

Semi-automated irrigation systems use bottled or premixed nutrients along with water, helping to ensure proper measurements. Pumping this solution into typically a drip system with simple injectors and control units to automate timing, offering the grower more zone control and time saved from manual watering and feeding.

The most advanced irrigation and fertigation systems on the market today control the mixing of nutrients from stock tanks to ensure the correct ratios are consistently used. They communicate as part of a larger IoT (internet of things) system that operates the entire grow facility, using sensors that can trigger waterings when needed and provide continual readouts of electrical conductivity and pH levels to ensure optimal levels are maintained. To prevent contamination and waste, excess water and nutrients can be recirculated and filtered safely back to the tank.

Soil Irrigation

●      Drip system - Nutrient-rich water is delivered from a holding tank through a series of pipes, valves, and polyethylene tubes with holes that release the formula as a steady and continuous drip at the base of the plant. This helps lessen evaporation and water waste. Again, the water and feed mix may be done manually as some smaller craft grows or is part of a semi or fully-automated system for larger operations.

A CNL device (Compensating Non-Leak) is ideal for ensuring nutrient-rich water is dripped consistently. This system compensates for pressure differences within the pipes and tubes. Non-Leak means there is only output if the water pressure is above a specific psi.

Adding distribution rings on larger pots gives better coverage to the more extensive root zones of more mature plants.

Drip assemblies are used by many to simplify the process. This involves a pre-cut spaghetti tube connected to the dripper on one end and drip stakes on the other. Some styles have 2-6 stakes, rather than one single stake, allowing for multiples in one pot or use in multiple pots at once.

●      Spray Stakes - Widely used in cannabis and hemp, spray stakes spray water in a container-sized pattern encouraging full root development. Spray stakes are placed near the edge of the container with a very low horizontal spray pattern, about an inch above soil level, to prevent the wetting of foliage that may cause disease. They need assistance with pressure compensation, so a pressure regulator will be necessary.

Depending on the manufacturer, spray stakes are available in various sizes and patterns, some offering down spray at a 45-degree angle, further protecting the plant. Some also have CNL functionality, assemblies with a CNL dripper that matches the flow rate of the stake assembled with spaghetti tubing. Once punched into the supply tubing, the system is ready to go.

Hydroponics

Growing cannabis in a soilless environment can produce incredible results, and there's more than one way to do it. Counterintuitive as it may sound, hydroponics is excellent for water conservation (using 80-90% less than traditional grows), and it's ideal for use in drought-stricken areas.

The word hydroponics itself means water (hydro) and labor (ponos). Taken from the Hanging Gardens of Babylon and the Floating Gardens of China, this is an ancient art form and one of the earliest technologies in agriculture that have been perfected with modern technology. Irrigation may not seem like a term that would be used much in this method of cannabis cultivation, and it may not need to be, especially since water is at the heart of it.

●      Drip - Simple, efficient, and versatile, it's the most popular of all hydroponics systems. While it is quite the same as drip irrigation using soil as a substrate, in hydroponics, the drip is aerated before being applied to the roots, which are protected by various mediums. It could be coco coir, rock wool, or clay pebbles; there is a wide array of choices.

●      Recovery drip systems allow operators to recover the nutrient water mix used for future reuse, but this requires monitoring and adjustments as plants use fertilizers and micro and macronutrients at different rates. This may cause the recovered fluid to differ from what went in.

●      Non-recovery drip systems need to be precise and more efficient than recovery systems. Highly accurate timers can ensure that substrates are moistened just enough to provide exactly what cannabis needs with little to no waste.

Drip systems also lend themselves very well to vertical gardening, where most of the water is applied from the top and drips down, either completely used up or recovered and then remediated for future use.

●      Deep Water Culture (DWC) - also known as raft - is a hydroponic growing method where cannabis roots are suspended in a well-aerated (oxygen-rich) nutrient and water solution. Aeration is critical as the roots are continuously submerged and have access to oxygen to not drown.

●      Ebb and Flow - much like ocean tides, this hydroponic method works by holding plants in a growing tray above a reservoir where they are periodically drenched in a nutrient-rich solution. The solution is absorbed by the growing medium, while excess drains back into the reservoir via an overflow regulator. This allows the roots to aerate, preventing the attack of pathogens. Based on a cyclic schedule determined by the condition of the growing environment.

●      NFT - Nutrient Film Technique is different in that plants are kept in a trough with neoprene collars or net pots to keep them in place. Most of the root ball directly beneath the plant is suspended above the flow of water and nutrients for constant access to oxygen, while the lower portions are submerged in the constantly recirculated solution. The grade of the flow channel beneath the plants is key to eliminating pooling and potential root rot. Aeration of the solution can be supplemented by nutrient oxygenation, air stones, or a waterfall effect, allowing the recirculated solution to fall back into the flow channel.

Aquaponics

The pinnacle of sustainability and organic growing, aquaponics combines aquaculture (the rearing of aquatic animals or plants for food - in this case, its fish) and hydroponics for a complete growth cycle with minimal input. Ammonia-rich fish waste is broken into nitrates by bacteria; this natural water/feed solution provides essential nutrients to cannabis plants, and in return, the plants clean or “filter” the water for the fish. This symbiotic relationship creates a closed loop system where the only necessity is fish food which could also be grown.

Successful operations enjoy faster harvests and higher yields from clean, vigorous plants, not to mention a continual source of food from the harvest of the farmed fish. They are, after all, another potential source of income.

●      Aquaponics uses fewer chemicals and water than a standard hydroponic system.

●      Easily farmed fish that thrive in tight quarters, such as tilapia, perch, and trout, are commonly used in aquaponics.

●      Double root zones are employed with soil or hydroton clay balls in the upper portion, held in place by burlap or plastic mesh, allowing roots to grow into the hydroponic system. This upper layer allows for a place to add extra nutrients necessary for flowering without contaminating the cannabis-filtered water for the fish.

●      Set up of an aquaponic system is often a more considerable expense and takes more time than a soil grow.

●      A water heater and additional water pumps may be necessary depending on the number and type of fish selected as well as the size of their tank.

●      Fish tanks require maintenance which means additional equipment. Commercial-size fish tanks need net covers, tank stands, fish nets for harvesting, thermometers, air pumps or blowers, and filters

●      pH monitors are necessary to ensure a healthy environment for the fish and plants. Happy fish means happy plants.

Accuracy is critical in aquaponics. Time must be taken in the design and initial setup to be sure all measurements and specs are accurate. This holds true for all methods of cannabis cultivation, particularly with irrigation and fertigation systems. Errors and miscalculations can create waste and cause detrimental damage to a facility and the failure of an entire crop - or two, as in aquaponics. On the other hand, a successful setup and proper maintenance of the facility’s irrigation system will be a pivotal component to the harvest's success.