Nursery Irrigation

Whether you're irrigating field grown nursery stock, containers of any size, hanging baskets, bedding plants, or any other greenhouse crop, Poly Drip has the products and the know-how you need to get the job done.

Growing in the field

1. Drip Irrigation

Root Zone: The length of the row will determine the size tubing required. The objective is to evenly wet the row and manage the water in the root zone. Water that migrates out of this target zone is lost to the plant and represents a wasted resource. In most cases, you cannot apply all of the water needed in a day without losing water from the root zone. The result is that you will water more than once a day and as many times as necessary to supply the total amount required. We call this pulse irrigation. >> More

Fertilizer: It is often desirable to apply fertilizer and perhaps other materials directly through the irrigation system. This ability gives the grower the capability of applying all the fertilizer that the plant requires on a timely basis so that it is always there when the plant needs it to grow. Poly Drip can show you how to water evenly and fertilize evenly. The results are amazing!

Total Water Requirement: By multiplying how much water is needed in acres/day to irrigate our crop by the total acres we get the total water requirement per day for the project. We compare the total water requirement to the water we have available.

If we have an existing water source we can flow test it to determine how much water at what pressure is available. If no water source exists, we have the luxury of choosing one that fits our application. When we have measured our water source, both volume and pressure, it is time to decide how much area we want to irrigate at one time. This is called zoning.

What we're really trying to find is a flow rate for the system. It is often more economical to use as much water as is available at one time. However, this is sometimes not possible because we want to break the field up into areas with similar water requirements based on plant variety. Each individual design has its own particular requirements. Once a flow rate is chosen, then it's time to size our mainline and header piping. This should be done in a manner consistent with proper hydraulic design considerations such as velocity, friction loss, air/vacuum relief capability, flushing capability at appropriate locations, and elevation head loss or gain.

2. Container Irrigation

Irrigation of containers is different from field grown in that we have a confined space above ground subject to temperature extremes, artificial growing medium such as pine bark, excessive air movement around containers, and the force of gravity.

Problem: It takes the same amount of water to grow a crop in a container as it does in the field; however, there is no reservoir to store the water except for the medium, which is usually very coarse. If we apply too much water at one time, or in only one place in the container, the water will quickly channel through the media and out of the pot.

To help prevent channeling, small spray sticks are often used to spread the water over the surface of the container. However, these devices are not pressure compensating. In effect, the amount of water that flows from each one depends on the pressure feeding it. The amount of water can vary significantly down a line of pots causing variations in flow of as much as 50% from one end of a line to the other. This variation means that containers getting the least amount water have to be watered longer to satisfy their needs thereby over-watering the containers getting more (higher pressure). If the grower is injecting fertilizer into his system, the problem is compounded by over applying fertilizer in some containers while not getting enough in others.

The Poly Drip Solution: We use a pressure compensating drip emitter, typically 2-6 gallons per hour, to supply water to the container. This assures that we have the same amount of water available at each container provided the pressure is between seven and 60 pounds.

We attach to the outlet of the dripper a small diameter tube where the non-compensating drippers are spaced 6 inches apart. The length of this tubing is dependent on the diameter of the container. Typically we take three quarters of the diameter to arrive at a length for the tube. This tubing with a built-in dripper acts as a dispersion ring and evenly places the water at 6-inch intervals along the length of the tube.

The total volume of water going into the pot is divided among the secondary drippers and a dispersion ring thereby reducing the frequency and the weight of each droplet. The reduced weight of the droplet serves to overcome the force of gravity and allows the capillary tendencies of the media to move the water laterally to effectively wet the majority of the media.

Greenhouse Irrigation

There are many variations of greenhouse irrigation system layouts. The critical thing is to establish what crops will be grown (ex. Bedding plants, hanging baskets, propagation, six to 12 inch pots). The total volume of water required is dependent on what is being irrigated. Irrigation in containers generally requires relatively low flow rates per greenhouse, while propagation and bedding plants generally require overhead irrigation with comparatively higher flow rates per house.

1. Control of greenhouse irrigation

Since all greenhouse irrigation applications require high frequency irrigation, automation of these types of systems using an irrigation controller is the rule rather than the exception. Depending on the specifics of the crop, the controller should offer the capability of multiple programs, multiple start times within each program, and in the case of propagation the option to program in seconds and minutes for a given window of operation time (called a loop). It is virtually impossible to irrigate greenhouse crops efficiently without the use of automation. The cost of automation is minuscule compared to the cost of labor to effectively irrigate greenhouse crops.

2. Hanging Baskets

Hanging baskets are most effectively watered using a dripper with a flow rate of half-gallon/hr installed on the lateral line attached to a structural member of the greenhouse. A small diameter tube is attached to the outlet of the dripper. At the other end a plastic weight rests in the basket.

The dripper should be pressure compensated and equipped with a device that allows the watering to begin instantly when the pressure rises above a certain point. It should also shut off instantly when the pressure drops to that point. All devices connected to that particular valve will start and stop irrigating at precisely the same time.

All baskets will be watered evenly. Greenhouse growers almost always inject fertilizer through their water. The equipment described above assures 94% distribution uniformity. Each pot gets the same amount of water and nutrient. Uniformity in irrigation leads to uniformity in production. Uniformity in production means a higher value crop. The goal of the grower should be to produce as uniform a crop as is technically possible.

3. Bedding Plants

Bedding plants are typically grown on benches or on the floor with walk isles between the blocks of plants. Installation required for designing a system includes the width of other tables or blocks, length of the tables or blocks, and the height of the plant material at maturity. This scenario usually calls for an overhead device being installed on lengths of tubing called drops. Sprinklers that produce small droplets are installed on the drops and spaced appropriately for the performance of the sprinkler.

It is desirable that the pattern of the sprinkler be confined to the width of the table or block. These sprinklers are also equipped with anti-leak devices to assure that they start and stop simultaneously. Since cycle times are usually short, it is important that the best possible distribution uniformity be achieved. This is done by carefully selecting the flow rate of the device, the diameter of its pattern, and the spacing required down the lateral to achieve the desired uniformity.

4. Propagation Systems

Propagation systems are similar in all respects to bedding plants except that the irrigation device is most often some type of mister or fogger. In this application we desire only to keep a small amount of moisture on the surface of what is being grown. We do not want to saturate the media.

This is where we find typical cycles of five seconds on, five minutes off from six o'clock in the morning until six o'clock at night. Because the droplet size of the devices available for this application is so small great care must be given to proper spacing of the devices. Typically the diameter of a mister would be limited to 5 feet. If there is any wind movement in the greenhouse it will greatly affect the pattern of the system.

5. Bench Pot Watering Systems

The most beneficial selection of product for this application is to choose a dripper (one half to two gallons per hour) and divide it's flow rate among multiple containers (4-8). Again, we would select a pressure-compensating device and attach a multiple outlet adapter to the outlet of the dripper.

Small diameter tubes are then connected to the multiple outlets of the adapter and run to each individual container. A small stake, which serves as a secondary dripper, is put into the tubing and installed in the pot. Each pot receives the same amount of water in the same amount of time. Flow rates may range from as low as 1/8 gallon/hour to 1/4 gallon/hour per container.