Key Takeaways

• TAPS enables direct comparisons. UNL-TAPS provides a unique way to compare irrigation decisions because participants manage crops under the same field, weather and irrigation system conditions.

• Average irrigation near optimum. On average, TAPS teams applied irrigation amounts close to the optimum estimated by a crop growth simulation model. 

• Team results varied. More than half of the teams applied more water than the model-estimated optimum, showing that opportunities remain to improve water management.

• TAPS overages were smaller. Among teams that over-irrigated, the average excess was smaller than amounts reported in several Nebraska studies of growers outside TAPS.

• Balance matters. Both over-irrigation and under-irrigation carry risks. The goal is not simply to reduce irrigation but to better match water applications with crop needs.

• Benchmarking supports better management. Benchmarking can help producers evaluate irrigation decisions, improve water-use efficiency and support long-term groundwater stewardship.

Why Irrigation Benchmarking Matters in Nebraska

Irrigation is central to Nebraska corn production, but water supplies are under increasing pressure. Groundwater levels have declined in parts of the state, and recent droughts have also affected surface water deliveries, forcing some irrigation districts to reduce allocations or temporarily limit deliveries. These challenges make it increasingly important to evaluate how irrigation water is used. 

Irrigation benchmarking compares actual water applications with a science-based estimate of crop water needs. The goal is not to blame producers, but to identify opportunities to improve irrigation decisions while protecting yield and profitability.

Why TAPS Is a Useful Platform for Studying Irrigation Decisions

The University of Nebraska-Lincoln’s Testing Ag Performance Solutions (UNL-TAPS) program provides a unique setting for studying irrigation management. In TAPS, producer teams make real crop management decisions on university-managed research plots. Teams compete on outcomes such as yield, profitability and input-use efficiency.

Because teams manage plots under the same field, weather, irrigation system and competition framework, TAPS creates a “level playing field” for comparing decisions. This helps researchers better understand how irrigation choices differ when many of the usual field-to-field variables are removed. Under these shared conditions, differences in irrigation are more likely tied to management choices, decision-making styles and perceptions of risk.

How the Study Estimated Optimal Irrigation

In this study, we used multi-year TAPS data and a crop growth simulation model (DSSAT CERES-Maize) to estimate optimal irrigation amounts. The model was calibrated and validated using TAPS field conditions, including local corn cultivars, soil properties, crop development and yield data. This step is important because benchmarking is only useful if the comparison point is realistic. A locally calibrated crop model can provide a more accurate estimate of crop water needs than a simplified assumption or generalized recommendation.

The model-estimated irrigation amounts were then compared with the irrigation amounts applied by TAPS producer teams. Non-producer teams were excluded, leaving 37 producer teams in the analysis.

TAPS Teams Were Closer to Optimal Than Earlier Studies Suggested

Across the study period, the average difference between producer-applied irrigation and model-estimated optimal irrigation was only 0.16 inch. This means that, on average, TAPS teams were close to the model-estimated seasonal irrigation amount. About half (54%) of teams applied more irrigation than the model-estimated optimum. Among those teams, the average excess irrigation was 2.3 inches. 

The level of over-irrigation found in this study was considerably smaller than reported in several earlier Nebraska studies and suggests better irrigation decision-making by producers than previously found. Two factors may help explain this finding: the study’s improved modeling methods, which produced more accurate estimates of optimal irrigation, and TAPS participants’ motivation to manage water carefully.

The practical message is encouraging but still important: many well-managed producers may already be closer to optimal seasonal irrigation than earlier studies suggested.

Both Over-Irrigation and Under-Irrigation Carry Risks

One important lesson from the study is that irrigation management should not be viewed only as a question of applying less water. Applying too much water can reduce yields, increase pumping costs, reduce water-use efficiency and contribute to unnecessary groundwater withdrawals. But applying too little water or applying it at the wrong time in the season can also reduce yield.

In this study, simulated yields under producer irrigation averaged 219 bu/ac, while yields under model-optimized irrigation averaged 235 bu/ac. That represented an average yield increase of about 7% under the optimized irrigation scenario. Most of the simulated yield increase occurred in plots that were under-irrigated by producers.

Producer Decision-Making Explains Much of the Variation

Producer-applied irrigation varied more than model-estimated optimal irrigation. Actual team irrigation had a coefficient of variation of 44%, compared with 21% for the model-estimated optimal irrigation.

Because TAPS teams operated under the same field and weather conditions, this difference suggests that human decision-making played a major role. Factors may include:

• Expectations about future rainfall
• Concern about crop stress
• Comfort with risk
• Management style
• Trust in irrigation tools or recommendations
• Past experience with dry periods or limited water supplies

This is an important reminder that irrigation management is not only a technical decision. It is also a risk-management decision.

Final Takeaway

The main lesson from this TAPS-based study is that Nebraska irrigation management is more nuanced than simply saying producers apply too much or too little water. Many TAPS teams were close to the model-estimated optimum, and the magnitude of over-irrigation was smaller than reported in some previous studies. At the same time, the wide range of irrigation decisions shows that opportunities remain to improve water-use efficiency and protect yield.

Benchmarking tools, when carefully calibrated and used as part of producer education, can help Nebraska irrigators make more informed decisions and support long-term stewardship of the state’s water resources.

For more information, view the open-access journal paper.