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Water Use Efficiency In Agricultural Trickle Irrigation Systems

Water Use Efficiency In Agricultural Trickle Irrigation Systems
By Andy Yencha and Leon Ressler
Trickle irrigation was first introduced in the 1960’s and 1970’s with the development of tubing and header lines which made the system function. A trickle irrigation system is most suited for high value produce crops and the trickle tube is usually buried in the root zone at planting time. Sometimes if the weather turns dry after planting the trickle tubes could be placed on the surface. The tubing is made with evenly spaced emitters where the water slowly drips out leading to the nickname “dripping irrigation”. It reduces water use approximately 50% compared to overhead sprinklers.
The system starts with distribution main lines which deliver water to the fields which are above ground and could be aluminum or polyvinyl chloride (PVC). Then the water flows through submains which are often layflat lines that collapse into a flat shape when empty. Connectors or couplings connect the layflat to the trickle tubes. A number of different types of tubing are available with different emitter spacings, range of operating pressure, and wall thickness.
A key part of successful trickle irrigation systems is filtration to remove any contaminants from the water supply. This is especially critical if the water supply is surface water from a pond or stream. Water that is not filtered could result in clogged emitters and cause failure of the system.
In order to get maximum efficiency from the trickle system, one needs to manage the water application. Part of that is understanding the water holding capacity of your soil which is influenced by both the soil type and soil depth. Knowing your water holding capacity is an important part of scheduling the irrigation. An appropriate strategy is to irrigate when the soil drops to 50% capacity.
One tool to assist in scheduling irrigation is a tensiometer. Water is held by the soil particles and as the soil dries and the water remaining in the soil is less, the soil particles hold the water with ever greater tension. Tensiometers are a tube filled with water which has a porous ceramic tip and a pressure gauge on the top. As the soil dries out the tension between soil particles and water increases. This tension also starts to draw water through the porous tip on the tensiometer and the tension created is measured by the gauge on the tensiometer. Thus the tensiometer is one way to measure water depletion in the soil by reading the pressure gauge on the top of the tensiometer. While this is a useful tool, tensiometers require maintenance so some farmers go with their judgment based on their experience to schedule irrigation.
Trickle irrigation systems require regular maintenance for successful operation. This includes regular cleaning of the filters and water treatment to control bacteria, algae, and slime growth in the system.
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