Drip Irrigation

What is more correctly called micro-irrigation evolved from the agricultural fields of water starved areas in the world, primarily the Middle East, Australia, and Southern California.

Micro irrigation includes several types of hardware. Emitters and mini sprinklers are the two primary types of distribution hardware. The hardware shares the characteristics of:

Low pressure required to operate
Low rate of application
The corollary of a low rate of application, longer duration applications

Lower Pumping and Lower Material Cost

One of the initial attractions of low pressure and low applications rates is less cost in materials. Less cost related to pumping, and the use of smaller pipe and tubing sizes due to less water conveyed on a per-minute basis.

Effective Irrigation into the soil (water) reservoir

The low application rates are effective in a variety of soils. In tight clay soils water can be applied slowly enough to eliminate the opportunity for run-off. A low application rate can also be efficient for irrigation in very sandy soils. Assuming an understanding of how fast water moves through the given soil, the scheduling of drip irrigation systems can be fine tuned to fill the soil water reservoir, while minimizing loses to evaporation, run off, and deep percolation.

Uniformity

Micro-irrigation has the potential for high application uniformities. Just as with other types of hardware, if it is not installed correctly – for example pressure compensating devices are not used in situations of varying elevations, or the spacing of the hardware is inappropriate, the uniformity will suffer. However, if the system design, installation and maintenance are appropriate for the crop, then there is the opportunity for very high application uniformities.

Irrigating Root zones

With careful location of emitters water is discharged directly into the root zone. Young plants should have emitters placed toward the outer edge of the rootball to encourage the roots to spread into the surrounding soil. Over time the emitter placement should be adjusted, moved further away from the trunk of the plant, and more emitters added depending on plant water need. If these installation details and subsequent system enhancements are made, the plant will have optimum conditions for growth, combined with greatly reduced chance for water waste.
In landscaping, there are groundcover plants that spread via rooting and trailing as they grow. For this type of plant, individual emitters are not the best solution. Either mini-sprinklers, or conventional low precipitation spray heads are likely to be better solutions.

System Management

Any irrigation hardware requires routine inspection. This is especially important for micro irrigation. This hardware is easy to undermine – and vulnerable to damage. One of the significant challenges is most emitters are difficult to inspect, or are installed so they are visible and are more vulnerable as a consequence. The diligent and routine inspection of the hardware is part of the cost of ownership, and needs to be addressed as such during consideration of the system installation.

Conclusion

There are specific applications where micro irrigation is the best solution by far. Examples include a hedge, sparse plantings of like/kind plants, container plantings, very narrow areas, and situations where overspray can’t be tolerated. That said, it is not the answer for every situation, and its choice should be carefully thought through to ensure a viable long-term solution.

Delivery Systems Articles • Posted on 02/22/2009 • Permalink