"Uniformity of irrigation is an important, possibly the most important parameter of greenhouse horticulture", says Stefan Bakker, product manager at Revaho. With a parameter he means a variable, measurable property whose value is a factor of the properties of a system, such as water. Uniformity of irrigation, both in quantity and composition, leads to optimal growth when other growth factors such as light and air are also uniform.
To indicate the scale for the uniformity of an irrigation system, the product manager gives the following example. For example, a 12-hectare pepper company has between 300,000 and 350,000 drippers on one irrigation system. "If on a summer's day you provide thirty times an irrigation of 200 cc of water, that comes down to about 10 million water shots. These must always be the same, for the first as well as for the last plant. That is quite a task!"
The irrigation system must therefore have a high degree of accuracy in order to achieve this. For the uniformity of the system, three elements are important: the quality of the components, the design and the correct use of the system.
For the perfect quality of the product components in the system, the product accuracy must be in accordance with a limited tolerance. The production of drippers must therefore always be the same in order to ensure uniformity in irrigation.
The installer plays a major role in the design of the system. He must convert the wishes of the user into the elaboration of the system. The uniformity of the amount of water that the system can supply must match that of the grower. The correct use of the system is a point for the grower himself. Bakker: "The cooperation and exchange of knowledge between the producer, installer and grower ultimately determine whether the uniformity of the irrigation of a spray or dripper system is as optimal as possible."
Equal water distribution
When using a spray system, there is a difference in the water distribution in a cut flower crop and pot plant cultivation. "When irrigating, uniformity counts as the most important parameter. Irrigation water in the open field spreads better than in pots, because water does not spread from one pot to another. Especially with very small pots the grower wants to have the same amount of water in each pot. With a large pot or container, uniformity is faster. In order to achieve the optimal result, the right product components and use of the system are therefore important. Because irrigation of small cuttings and plugs in trays or jars requires many more small droplets than a large pot or container," reports the product manager.
Composition of water
Uniform composition of the water is related to: temperature, EC and pH value, oxygen level and disease pressure of the water. Is this the same in the whole irrigation system or is it different at the beginning and end of the system? In practice, it turns out that when the companies grow and the acreages per system increase, the uniformity of the composition decreases and changes. This has to do with the travel time, the time the water takes to move through the system. Because of the travel time, plants at the beginning of the system receive 'different' water than the plants that are the furthest away from the dosing unit. The travel time also determines the uniformity of the irrigation.
Specify travel time in quotation
Bakker: "When the composition of the water is the same every day, the difference between the first and last plant is less. But if a grower gives a different fertilizer composition every day or during the day, the difference is greater."
Because the travel time is in the system design, it is important for a grower to know this effect and to take this into account if he wants to make a change in the water composition. "The travel time, which can be calculated, must be included as a parameter in the quotation process. Because if a grower knows that his system has a certain slowness, it makes little sense, for example, to use a lower EC value or plant protection product on a hot summer day. The changed composition of the water can only reach the last plants the next morning."
Source: Glastuinbouw Waterproof