Over the last few years, technological advances have helped field growers gain better control over many of their production parameters; however, rainfall and seasonal conditions remain uncontrolled. By moving part or all of the production indoors or into a greenhouse, growers can gain control over the changing environmental conditions of temperature, humidity and water application that are affecting the yield and health of the crops.
It has been stated that by 2050, agriculture will have to produce two times the current yield, using 70% of today’s inputs in order to feed the projected population. Thus, there is a growing trend toward Controlled Environment Agriculture production for vegetables, herbs, fruits and nutraceuticals. Growing in a structure enables growers to mitigate disease and pest issues, while the advances in microirrigation allow growers to deliver a precise recipe of nutrients and quantity of water to each plant. We are no longer working with measuring inches of water per acre, rather milliliters per square foot. Precision inputs and controlled environments allow for year-round production at a much higher density per acre, with a fraction of water usage required by conventional field production.
We are no longer working with measuring inches of water per acre, rather milliliters per square foot.
In Controlled Environment Agriculture, growers utilize conventional, root manipulating and cloth containers, as well as upright and lay flat bags. There is also a choice of soil or soilless media. The choice of substrate determines frequency and duration of the irrigation cycle. This method of frequent irrigation is called pulse irrigation and has led to advances in irrigation controllers.
In selecting an application method, the grower has several options governed by the container size, plant and media chosen. The use of microirrigation helps avoid water on the foliage and thus reduces the potential for disease.
There are several options when choosing irrigation emitters. The pressure compensating emitter maintains the same output rate regardless of the supply line pressure, if it stays between 15 and 50 psi. In addition, you can select a nondrip or non-leaking emitter that ceases output once pressure drops below a set pressure. By selecting non-drip or non-leaking pressure compensating emitters, all drippers turn on and off at the same time so that every plant receives the same amount of water and nutrients. This uniformity of application gives the grower predictable results, potentially aligning harvest with demand.
Additionally, the grower has options on what type of output device works best for a given application. One option is the drip ring, which is available in different diameters depending on the container size. These rings have multiple drip points that encircle the container, providing good application for containers up to 7-gallon size.
Another option is the drip stake. These are connected to the emitter with a small spaghetti tube and supply water to one point in the container. One emitter can supply multiple drip stakes, depending on the desired water volume and application rate being supplied to each plant. Quite often, growers will use multiple drip stakes per container, with drippers from more than one emitter. This redundancy provides a safety net in the event of an issue with one emitter.
The last option for water application is a spray stake that distributes water in a spray pattern instead of at specific points. The spray stakes are available in different angled patterns and flow rates depending on the container size chosen. The best use is for containers 7 gallons and larger. Typically, the spray stake is placed at the outer edge of the container and the output pointed toward the plant. Multiple stakes are often used in large containers to provide better coverage. Stakes are also available with a 45-degree downward angle. When used in smaller containers, they help avoid overspray, keeping all the water in the desired container. The use of spray stakes helps avoid channeling, which is when water moves quickly down the container without enough horizontal coverage.
When installed directly into the supply line, the spray stakes are not pressure compensating. To adjust for this, a 15 to 30 psi pressure regulator should be included in each zone to ensure proper operating pressure and better uniformity of volume and coverage.
These examples of microirrigation technology advances help growers gain more control over the production of their crops and allow for increased production yield.