Introduction To Hemp Irrigation: America’s Newest (Old) Crop
A plant once thought to be taboo now offers an extensive field of opportunities!
Hemp is one of the oldest but most quickly expanding crops in Agriculture. Grown by the Founding Fathers, Hemp helped to sustain early settlements in America. Today, this versatile crop can be used in a broad range of applications.
When planning your Hemp project it is critical to consider that growing hemp requires careful attention to detail. From seed to harvest, the process will require proper planning and preparation in order to be successful.
Irrigation is often a key factor in the success of any crop; drip irrigation is a great choice for hemp as it allows for precise water distribution, which helps to create an environment that produces a successful crop.
The Benefits of Drip Irrigation:
Control Disease and Save Water
Hemp is surprisingly resistant to dry conditions, however it requires more water than many would claim. This is particularly true when strong, healthy plants capable of turning a tidy profit are desired. While one could use traditional irrigation methods to water their hemp plants, this can create many problems. Disease, fungus, soil and nutrient erosion, water waste and uneven application of water are many of the problems encountered with center-pivot and similar style irrigation systems. Drip irrigation solves these problems and some that have not even been considered.
Optimum Soil Moisture
Drip irrigation provides a steady application of water to the soil. This application rate is slow enough that important nutrients are not washed out, run-off does not occur and evaporation is minimal. On the other hand, the application rate is fast enough that the moisture level of the soil can be kept at optimum levels. Drip irrigation delivers water directly to the plant’s roots, minimizing waste and maximizing efficiency. Do not spend time fighting erosion, fungus and disease when you can spend time expanding your business and growing techniques.
Fertilization and Amendment
Perhaps the biggest benefit in using drip irrigation for a hemp crop is the ability to run soil treatments, fertilizer, and nutrients directly through the irrigation system. A Fertilizer Injector can be used to send nutrients or amendments through the sub-main, out of the emitters to be delivered exactly where needed. This cannot be said for most other irrigation methods.
Modern fertilizer injectors allow for precise amounts of additives to be injected into the system; drip irrigation emitters are designed to provide precise volumes of water. These two factors combine to provide growers labor, time and money-saving methods of fertilization and soil treatment. Commercial growth of hemp requires precise delivery of water and nutrients; drip irrigation provides the precision necessary to minimize loss and maximize growth of both your plants and your business.
Drip provides a myriad of benefits over other irrigation methods. From better crop growth, to germination, to easier access to the irrigation area. If you’ve ever tried to walk a field watered with pivot irrigation, you know it’s not easy to traverse an area that is damp and soggy. Drip irrigation keeps the soil moist but not soaked. Perhaps best of all, drip irrigation significantly reduces surface moisture which means drip irrigation, indirectly, reduces weed germination and growth.
What is an Irrigation System?
Is an irrigation system the pipes and tubing that carry water? Is it the emitters that deliver the water to the plants? Is it the pump that moves the water, or the filter that cleans it? These are easy questions to answer as surely they are all components of an irrigation system.
But what about the pond from where the water is drawn, or the hill where a row of crops are planted, or the furrows between rows, or the laborers who work the field, or the satellite photos of the topography of the land? The answer of course, is that all of these are part of an irrigation system and all of them must be considered, from the early design phase, to the installation and storage when the growing season is complete.
Like all irrigation systems, success or failure is often determined in design. There are many factors to consider when designing an irrigation system, and drip irrigation is no exception. A carefully considered design that accounts for the most important variables is imperative to success. There are no short-cuts worth taking; any time saved in this step by circumventing part of the process will be paid for later at a greater cost.
Here are the first 3 steps to get you started on your project:
Know Your Field
One of the most important factors in the success of your system is accurate measurements of your field.
You will need to measure the dimensions of the field and account for any slopes or elevation changes, as the topography of the land must be taken into consideration when designing the system.
It may be worth investing in good surveying equipment. Many designers use GPS to assist in achieving the most accurate results.
Know Your Water Quality
It is important to know how much water your project will require. This can be easily calculated (# of plants x GPH or GPM= total volume of water needed). It will be important to consider peak water volume consumption.
You will want to test the flow rate of your water source to determine how much water can be delivered all at once. This will be the determining factor of how many zones will be needed. To test the flow rate of your water source, here is our flow rate calculator.
Make sure you are familiar with your water rights as this can impact water availability.
You’ll want to test your water quality, testing for chemicals, organic matter, minerals and overall condition of the water. If you are using grey or recycled water, you’ll want to strongly consider the filtration method you are using.
Lastly, you’ll want to check the water pressure (PSI) of your water source to determine what components and watering methods best suit your specific application.
Know Your Watering Method
You’ll want to determine if drip tape, drip line or drip emitters (drippers) are best suited to your application.
Things to consider when determining which method is best for your system: the configuration will depend on plant locations (how far apart they are spaced), row spacing, the topography of the field, row lengths, your soil type and the depth of installation.
Plant Location and Spacing:
You’ll want to space the emitters to be equal to, or closer than your plant spacing, never wider. With wide plant spacing, it is recommended to pick closer emitter spacings, such as 12” - 14”, so the emitters can supply water between plants for optimal root growth. Some hemp grows use spaces 4’ - 6’ between the different rows to offer room for plant growth.
When determining how close to make your rows, you’ll want to consider that they should be close enough to each other, as well as the plants, to supply the proper amount of water to the root zone.
It is typically recommended to space rows of hemp grown for cannabis or cannabinoids between 4’ to 6’. This allows for plant growth and easy access to the plants in the field.
Industrial hemp grown for fiber and other industry-related goods, can be planted more densely, as these plants are typically smaller and more compact.
It is important to avoid spacing rows too far apart, as this will result in inadequate watering.
Topography of The Field:
Drip irrigation components are all sensitive to pressure, as drip systems typically run on very low pressures.
In systems with slopes or elevation changes, this will be incredibly important to take into consideration when designing your system.
With steep slopes, the pressure at the end of the line will increase, sometimes too much, causing a flooding effect at the bottom of the line. Pressure compensating devices are usually a good choice in this application.
In systems with elevations or upward slopes this will experience pressure loss, and may not even receive water at the end of the line if enough pressure is lost, resulting in inadequate watering throughout the line. Higher operating pressures or lower flow emitters can help to remedy pressure loss.
A good rule of thumb is to be at least at 90% emission uniformity (EU%). Higher uniformity leads to better, healthier crops and ultimately, higher yields.
It will be important to consider how long your runs will be, as this will determine the best size tubing or tape to use.
Typically ⅝” tape is recommended for runs that are up to 550 ft. For longer runs up to 1200 ft. ⅞” tape is recommended.
4’ - 6’ Row spacing recommended for all rows. If you plan to bury your tubing, 2” is usually sufficient. 12” - 14” emitter spacing typically recommended. (Individual system specifications and capacities will vary).
Burying and Coverage:
Drip tape and drip line can be covered with mulch or another type of light coverage to help control weeds, temperature, and overall reduce labor needed.
2” below the surface is the recommended installation depth if you will bury your tubing or drip tape. The subsurface installation helps to create optimal moisture levels in the soil for greater plant growth.
It will be important to ensure that the soil used does not contain heavy metals that can be absorbed by the plants.
Your Soil Type:
There are various different soil types which feature different capillary action; how the water moves through the soil. Depending on the soil type you have, you will want to match the emitter flow rate to the capillary action of the soil. To learn more about soil type, here is our helpful "Know your soil type" article.
Hemp specifically thrives best with sandy soils that have good aeration.
If your flow rate is too high for your soil type you may notice runoff created from your field.
It will be important to ensure that the soil used does not contain heavy metals. Heavy metals can be taken in by the plants and can end up in the foliage which ultimately lowers the value of the crop due to toxicity.
It will be paramount that you test your soil to ensure you have clean, organic soil without heavy metals.
Products to Consider in Your Hemp Irrigation System
Air vents are all too often overlooked in an irrigation system, yet they are the single least expensive item that can be purchased to protect the components of the system. There is no such thing as a pipe or tube without air. Even a closed-loop system, thoroughly vented the first time it is turned on will have air in the pipes as it operates. Air can be created at every fitting and every valve; as the water hits these components, the oxygen atom in the water molecule can break apart. When this happens, you not only have air from the oxygen atom but from the two hydrogen atoms as well. As these gases travel down the line they can slam into components (fittings, valves, etc) and cause significant damage to them over time. In this way, an irrigation pipe can never really be clear of air. For this reason air vents are a necessity. The initial investment for them is negligible compared to many other components, and the capital they save protecting the components in the system far exceeds their cost.
Air vents help:
Prevent cavitation of your pipe and tubing
Control water hammer and its associated wear on components
Provide up to 20% energy savings due to increased pump efficiency
Protect components even when there is no water hammer. Air travels approximately 19 times faster than water, small air bubbles can cause significant damage at this velocity even if it is inaudible.
If you’d like to learn more about air vents and their importance in an irrigation system, we wrote a short article that has more details here: Why You Need Air Vent/Vacuum Relief in Your Irrigation System.
Air vents and vacuum relief are available here: Vacuum Relief and Air Vents
Drip Line and Tape
There are two types of drip line commonly used in drip irrigation of hemp: heavywall and thinwall. Heavywall is often referred to as dripline and thinwall is often referred to as drip tape. The most significant difference between the two, as their names imply, is the wall thickness. These emitter lines come in pressure compensating and non-pressure compensating options. Choosing between the two is not quite as easy as slope = use pressure compensating, flat = use non-pressure compensating; there are other variables that should be considered.
Uniform distribution of water is essential to a successful grow. When professional designers design an irrigation system they aim for at least 90% uniformity to ensure the plants receive nearly equal amounts of water. Uniformity below that 90% mark can cause some plants to receive too much water or some to receive too little water; sometimes both can happen on the same system depending on the issues with distribution. If the application rate of water exceeds the infiltration rate, run-off and erosion can occur as the water saturates the soil. Drip irrigation makes uniform distribution significantly easier than other irrigation methods, even on sloped fields.
Pressure Compensating vs. Non-Pressure Compensating
The old adage that says, where there are slopes, pressure compensating emitters will be required, is not entirely true. Heavywall driplines with non-pressure compensating emitters are good up to a 1.0% slope, while thinwall driplines are good up until about 1.5%. Beyond 2% uniformity will often drop below that 90% mark. There is an important exception to this, however. A slope can actually be used to improve emission uniformity.
In low pressure drip irrigation systems, particularly those using long rows, the pressure at the start of the row will be much greater than at the end due to friction loss. If a non-pressure compensating dripline is placed on a downward slope, the gravity can be used to balance pressure between the start of the run and end of the run. Short runs on slopes or runs on steep slopes will benefit greatly from pressure-compensating emitters. Non-pressure compensating emitters on a steep slope will likely experience substantial variance in emission rates.
Another situation in which non-pressure compensating emitters are advantageous are very low flow systems that have long (most of the day) watering cycles. In these systems, if soil moisture falls too low, additional pressure can be added to increase the rates of water application. This allows the grower to catch the soil moisture level up to optimum levels. Pressure compensating emitters cannot increase their distribution rate with this method; only an increase in the watering cycle can provide more volume, however if the watering cycle is already very long this may not achieve the desirable results, likewise if the application rate is too far below the infiltration rate.
One of the biggest concerns growers have is clogged emitters. To this end, dripline manufacturers create emitters that have a turbulent flow path and even have filtration installed at each emitter inside the dripline. This reduces, and in some cases, eliminates clogged emitters. One method to tell how well the emitter’s filtration and turbulent flow path reduces clogging is to check the manufacturer’s specs and see what minimum filtration is required. The finer filtration required, the higher the likelihood of clogged emitters. A lower recommended filtration is the sign of confidence in the technology inside the dripline.
Heavywall dripline can be found at this link: Heavywall Driplines
Thinwall dripline can be found at this link: Thinwall Dripline and Drip Tape
Many irrigation experts argue that filtration is the number one most important component in your system. Filtration directly impacts the success and performance of the system. If you have clogs in your system, this can have devastating results. Failure of the primary filtration system can mean failure of the project in its entirety.
In bigger systems there are a few different types of filters to consider:
Semi-Automatic Filters - (Amiad 2" T-Super Filter w/Brushaway Assembly)
How it works: This semi automatic filter uses a Clogging Indicator, a feature that is mounted on the filter pressure check points. This indicator acts as a status light. When the pressure differential across the screen reaches a pre-set value of 7 psi, the red button will light up to indicate that the filter needs to be cleaned.
Why use it: Semi-Automatic assemblies provide a quick and efficient way for cleaning filters. A simple turn-of-a-handle mechanism cleans the filter's screen.
This saves both time and labor, as you do not have to disassemble the unit to clean it.
Automatic/ Auto-Flushing Filters - (Amiad Mini Sigma Automatic Filter and Amiad TAF-750E Series Filters)
How it works: These filters are known as “automatic” because they do not require any manual cleaning.
The Amiad Mini Sigma, once activated, the flush valve opens to atmosphere, which then creates a powerful backwash stream that flows through the hydraulic turbines causing them to rotate and the scanners to spin. This creates a strong suction force at the scanner nozzles which ensures the entire screen is swept clean and debris is flushed out the discharge valve.
The self-cleaning cycle is initiated by any one of the following conditions:
Signal from the DPS is pre-set at 7 PSI.
Time interval parameter set at the controller.
Manual start, triggered by the ADI-P mobile app (within Bluetooth range) or via electronic controller keypad.
The Amiad TAF Series Electric Filter is an automatic, self-cleaning filter that uses a 110V controller, solenoid and sensor to automatically perform a self-cleaning flush process. You no longer have to shut down your system, take apart the filter, and remove the screen to clean. As debris cakes up inside the filter element screen a pressure differential across the screen triggers the sensor to perform the quick suction scanner cleaning process. This process is also programmable at specific time intervals or can be manually started when necessary.
Why use it: This provides the most efficient and labor-effective cleaning solution among any filters. With no manual cleaning required, automatic filters offer an innovative way to save time and labor money when it comes to maintaining and cleaning your filter.
Manual Filters: By default, all of the other filters we carry are manually cleaned filters.
How it works: You will need to disassemble the filter and remove the screen in order to clean the internal element. Each filter is normally pretty straight forward with small variances between models and brands. You’ll start by unscrewing the body housing of the filter, and remove the internal element. Once this has been removed you may need to soak, spray or scrub the element clean. Please note, these elements can be delicate and can be damaged if you are not careful in the cleaning process.
Why use it: These are often the most inexpensive solutions. However, in the long run, labor time and/or costs may not ultimately make these the most cost-effective solution. If you have a smaller system, or have extremely clean water, you could use a manual filter. These do require regular cleaning and maintenance.
To learn more about filters, here is our Filter Buying Guide.
Sub-Main and Mainlines
Sub-main pipe and tubing is an important consideration. While the pipe used prior to the valves may be an easy decision, the sub-main decision is not always easy. There are three type of sub-main we see used commonly: Layflat, Oval Hose and Flexnet. Each have advantages and disadvantages which will be discussed briefly below.
Layflat was originally designed to simply be pump discharge hose, but we see it mostly used for a drip tape manifold these days. Layflat is economical in price. Though it requires special fittings to get drip tape runs connected, it is a common enough manifold hose that many laborers have experience installing these fittings. Layflat is also durable and can enjoy a good life expectancy through normal use. The biggest complaint about Layflat is its tendency to twist, turn, snake and sometimes even elongate when it is pressurized. While manufacturers have experimented with different weave styles to try and solve this, it is still a concern of many growers.
Economical, affordable and common enough that many have experience with it
Durable, can expect a good life expectancy when used within specification
Can twist and elongate on pressurizations. This can increase labor costs to some degree
Requires teardrop fittings for the tape rows. These are not common fittings and take a bit of exposure to get used to their installation and leaking is likely to occur at times
Oval hose sub-main tubing is simply poly tubing sized for agricultural use. Popular brands include Toro Blue-Stripe and Jain Oval Hose. It is regarded as durable, but those who have experience with poly tubing will know it’s not quite as durable as Layflat. Layflat is made with a weave of resins, oval hose is constructed of solid polyethylene.
Oval hose uses barbed take-off fittings for its tape rows; these barbed fittings are less prone to leaking than teardrop fittings and are easier to install and use. The oval shape is simply to make storage and transport more economical, most brands are 98% or more round once pressurized. The black color is a concern for some growers; when exposed to direct sunlight the tubing can reach temperatures higher than is safe for plants.
While the tubing itself is UV treated and can withstand UV exposure, the water inside can become heated to temperatures unsafe for plants. In these cases it is advised to place it in the shade, create some shade or even use it sub-surface.
Economical and easy to use.
Durable through normal use, not quite as durable as Layflat in most cases
Becomes round on pressurization
Experiences less leaking than Layflat installations
Due to its color, heat is a serious concern. It is a variable best addressed prior to installation and use.
Flexnet sub-main was designed specifically to be used as a drip manifold. To that end it performs the function the best out of the three as it is a solution that was created as a direct response to grower feedback. It is remarkably durable, easy to use and experiences virtually no change in shape, size or orientation when pressurized. The take-off fittings used with FlexNet thread into the hose’s female pipe threaded inlets; this means compatible fittings are easy to find as it uses nominal pipe sized outlets.
Flexnet has fewer problems with heat as it is white in color. The initial cost of Flexnet is higher than Layflat or Oval Hose in most cases, however this can be recouped through lowered labor costs. Flexnet is significantly lighter in weight than other options and is significantly less expensive to transport and store on a per foot basis.
Designed specifically for use as a drip manifold
Very durable compared to other options
White color mitigates heat issues
Does not twist, snake or elongate upon pressurization
Wide variety of compatible fittings and easy to use ½” NPT outlet ports
Layflat is available here: Layflat Tubing
Oval Hose is available here: Oval Hose
FlexNet is available here: FlexNet Submain Pipe
Fittings for the three manifold hoses enjoy cross compatibility and the fittings for one can be used for the other. These include couplings, end plugs, elbows, tees and more. The biggest difference in fittings used is in the take-off adapters. Take-off adapters are the fittings used to connect the drip tape to the manifold.
Layflat: Layflat take-off adapters are what’s known as a Teardrop” fitting. Teardrop fittings take some practice to get used to the installation, however proper installation is important to prevent leaking at the fittings. Teardrop fittings require the hex handled installation tool and it is recommended to use the Layflat cutting tool to create the correct sized hole. These fittings take more use, but once the technique is learned the installation becomes quick and easy.
Oval Hose: Oval hose take-off adapters are the traditional barbed adapters used to run tape rows from poly tubing. They are available in several barb sizes with the larger barbs being used in high flow or very long tape rows. These are easier than teardrop fittings to insert; you simply punch a hole in the wall of the tubing with an appropriately sized punch and insert the barb into the hole, the other end of the adapter connects to the drip tape. The most common complaint from oval hose fittings is leaking over time, but their ease of use and economical price point makes them a popular choice.
Flexnet: Flexnet takeoff fittings are the easiest out of the manifolds discussed in this article. The outlets on the Flexnet are simple ½” FNPT outlets. The take-off adapters for Flexnet simply thread into the outlet and then the barbed end connects to ⅝” or ⅞” drip tape. Flexnet take-off enjoys the most leak-free solution out of the three, however they are limited to the outlets on the Flexnet manifold. Layflat and Oval Hose enjoy the flexibility to have take-offs installed almost anywhere along their length, while Flexnet has the pre-installed outlets.
Layflat specific fittings are available at this link: Layflat Fittings
FlexNet specific fittings are available at this link: FlexNet Fittings
Oval hose fittings are shared with Layflat insert fittings. The insert fittings are compatible with both Layflat and Oval Hose, and in some cases FlexNet as well.
Nutrient Injection and Fertilization
Your system flow rate. It is paramount you know the flow rate (GPM/GPH) your system will use at once. As this is one of the factors that determines what unit you can use.
Your feed/induction ratio needed. This will be highly dependent on your individual system, the plants, and the nutrients you choose to use. The induction ratio is how much of the fertilizer will be injected into the system. Normally this is done in ratios (1:100, 1:400, 1:1000...etc.) Or, it can be done in percentages (.1% - 5%).
An important side note that simplifies things significantly: Make sure your volume of water and induction ratios are in the same unit of measurement. Mixing up “Litres per hour” vs. “Gallons per hour” can really throw off a system. So the unit of measurement will be something to consider when determining the right injector.
If you are unsure of the unit of measurement an injector uses, please don’t hesitate to ask! We will always be happy to help out. Additionally, free litres to gallon converters can be easily accessed using google.
The pressure (PSI) within your system. PSI will be a consistent factor in most irrigation components including fertilizer injectors.
A few things to note:
If you will be using this system under constant pressure you’ll want to ensure the system can withstand it. Most fertilizer injectors cannot withstand constant pressure.
If you have a system with extremely low pressure, you’ll want to ensure you meet the minimum PSI (and flow rate) requirements in order to ensure proper injection.
If you have a system with very high pressure this will also be important to take into consideration, as all fertilizer injectors do have a maximum PSI rating. In this case, you could either look for fertilizer injectors with a high pressure rating, or, you could install the fertilizer injector downstream from a pressure regulator (if one will be used).
Nutrients and Fertilizers - This is the last main factor to consider when you are determining the best system to use. You’ll want to consider:
If you will be using multiple fertilizers, as this will require a more complex solution than many of the standard fertilizer injectors which use only one nutrient.
If you will be using harsh chemicals such as chlorine. This is important, as not every injector is made to withstand harsh chemicals.
If you will be using a non-water soluble fertilizer. It is strongly recommended to use only 100% water soluble fertilizers and nutrients in drip systems.
Thank you for taking the time to read our short guide. If you have any questions regarding its contents, the products mentioned within or irrigation in general, please don’t hesitate to reach out to us at firstname.lastname@example.org. We read and reply to every email we receive and would love an opportunity to provide support to you and your project. We look forward to hearing from you.