Center Pivot Irrigation Test Program

Properly designed sprinkler packages often achieve uniformity in excess of 90%. However, several factors can lead to decreased uniformity, including sprinkler component wear, clogged sprinklers, improper installation, insufficient pump flow, and leaks.

Lack of uniformity contributes to grower costs and wasted water resources. When an irrigation system demonstrates poor uniformity, irrigation depths vary – some areas being over-irrigated and some areas being under-irrigated. In the under-irrigated areas, potential yield benefits from irrigation are not fully realized. In the over-irrigated areas, excess irrigation is often lost to runoff or deep percolation. Over-irrigation can result in additional profit losses due to nutrient leaching. The profitability effects of under- and over-irrigation resulting from lack of uniformity are magnified when fertigating or chemigating.

Each test is normally conducted by two Extension agents and usually is completed in less than two hours. The pivot is set to a low application depth (e.g., 0.2 inches) and catch cups are placed at about 10 ft intervals along the length of the system. As the pivot travels across the catch cups, agents measure the travel speed of the pivot and indicate positions along the pivot where identifiable issues are observed. After the pivot has passed the catch cups, agents collect the cups and record irrigation depth at each position. Power meter readings at the pump may also be recorded so that cost of irrigating can be included in the test report. Field boundaries are either mapped on-site when the test is conducted or drawn from satellite imagery so that endgun shutoff recommendations may be provided with the report.

A measure of uniformity for your center pivot is the primary test objective. However, the test report includes a great deal of additional quantitative and qualitative information about your system. Some of the information in the report is shown in the list below. Examples of sample reports can be viewed under the “Sample Report” tab.

• Graph and map of irrigation depth in relation to center and tower locations
• Calibrated Percent Timer Chart
• Positions of observed issues (clogs, leaks, etc.)
• Estimated costs of under- and over-irrigation, $/ac/yr
• Estimated payoff period for sprinkler retrofit
• Endgun shutoff positions and savings
• Irrigation cost, $/ac/in. and $/in.
• Maximum application rate, in./wk
• Design vs. observed flow rate, gpm
• Design vs. observed system pressure, psi
• System dimensions (wetted area, wetted radius, machine length, endgun throw)

Target dates for each test are coordinated between the irrigator and area Extension agents. Tests are weather-dependent; agents will confirm appointments the day before the test. Please confirm proper operation of the system prior to the day of the test and address any known issues prior to the test (ex. (clogs, endgun rotation, drops hung on structure, etc.). Growers should plan to be available to meet agents to answer any questions about pivot operation and start the well and/or pivot. After the test has begun, growers do not need to be present during the test duration but should be available by phone for any questions.

Test results are available immediately upon completion of the test. The testing agent(s) will review results and follow up with you within a week following the test to review findings. Anonymized results from your test are collected in a database for aggregated data analysis. Nothing in the database contains personally or geographically identifying information, beyond the county level. A printed copy of results is also provided.

$125.00 per pivot. Cost includes test administration and printed and electronic copy of the report.

Visit the Center Pivot Irrigation Test Registration page and fill out the form.