Low Pressure System Irrigation Research

Suat Irmak

Low Pressure System irrigation set up in Clay Center, Nebraska.

Background
Some growers in Nebraska and neighboring states have small and/or irregular-shaped fields where installation of a center pivot irrigation system may not be feasible or possible. It may also be difficult to irrigate these fields with surface irrigation due to steep slopes or long furrow lengths. Most of these fields have been under dryland production. However, growers may have a desire to convert these fields to irrigated corn, soybeans, or other row crops.

Potential Applications of Low Pressure System
A new irrigation system, Low Pressure System (LPS), was introduced in 2004 by the Netafim-USA company (Netafim-USA, Fresno, CA). It is a relatively low-cost system to irrigate irregular-shaped and/or relatively small fields with limited water supplies. The system has high application efficiency when operated properly.

The system is operated under approximately 3 to 5 psi pressure, which is maintained in a ten-foot tall standpipe. An experiment using the LPS has been underway since 2004 at the South Central Agricultural Laboratory near Clay Center, Nebraska. The research is focusing on soybean yield response to irrigation, quantifying crop evapotranspiration, and crop coefficients in south central Nebraska. The first two years of research were completed in 2005. In addition to the results of the first two years of field research, challenges, issues, and experiences associated with using LPS and practical solutions to the issues continue to be documented and discussed. The system is also being evaluated in terms of it's adaptability and feasibility of application in developing countries, especially in areas where restricted water conditions limit crop production. The system can also be used as a gated pipe to furrow irrigate row crops.

Most of the components of the LPS are completely portable. This might be a good option for growers who are leasing their fields for short term periods as they could transfer the system to another field when necessary. The system may also be viable to irrigate small scale farms (i.e., organic farming). It appears that the system is more suitable for sandy or sandy-loam soils, especially for vegetable and fruit crops production than fine-textured soils such as clay or silt-loam soils. Currently the LPS is being tested at four locations in the U.S.: Colorado, Texas, Arizona, and Nebraska.

Overall objectives of the research with the LPS are to:

• Evaluate system efficiency and uniformity
  
• Quantify soybean growth and yield response to irrigation
  
• Quantify crop water stress versus yield relationship
  
• Evaluate economical feasibility and operational characteristics of the systems in terms of it's applicability in developing countries.

1. A float switch is located at the top of the stand pipe to control the water level.

2. Ten-feet tall, The stand pipe has a weighted bottom and is held with guide wires. It provides the operating pressure to the system.

3. The black tubing along the side of the stand pipe is the communication link between the float switch and the pressure valve.

4. The Pressure Regulator determines the water level and supplies constant water flow from the pump to the stand pipe.

Figure 2. Pressure regulator.

Figure 3. Pump to stand pipe

Figure 4. The operator can adust the Pressure Regulator to determine the water level in the stand pipe.

Figure 5. A "T" from the stand pipe carries water to two PolyNet lines. From the main lines, the water moves into emitters that have been placed down the furrows.

Figure 6. The LPS drip tape can be buried 2 to 3 inches underground, or left on the surface. The emitter lines can be buried or left on the surface and used as gated pipe, or gravity feed, with the drip tape.

Acknowledgments:

• University of Nebraska-Lincoln Agricultural Research Division
• South Central Agricultural Laboratory staff
  
• Netafim-USA

Disclaimer: The mention of trade names or commercial products is solely for the information of the user and does not constitute an endorsement or recommendation for use by the University of Nebraska-Lincoln or the author(s).