Over-Irrigation can Leach Nitrogen and Reduce Yield

Excess water in farm fields can damage crops, reduce yield, and can contribute to the leaching of nitrates and other nutrients into water sources. Proper management of irrigation activities is required to provide optimal moisture levels in the root zone, which is a major factor in achieving optimal yield.

Excess water can increase weed pressure and create conditions favorable to disease. On top of that, research has shown that each inch of leached water carries 5 to10 pounds of nitrogen with it. Considering that producers within the Lower Loup Natural Resources District (LLNRD) plant approximately 800,000 acres of irrigated corn each year, those leaching 3 inches of unused water lost an estimated 1.2 to 2.4 million pounds of nitrogen in 2022 alone.

That amount of leached, unused nitrogen may seem shocking. If that nitrogen was spilled in a small area, it would make headlines as an environmental disaster. When it is spread over nearly a million acres of the LLNRD it becomes invisible … except for the nitrates that end up in groundwater. Nitrate pollution rates in many areas of the LLNRD are climbing. What can irrigators do about it?

• Installation of flow meters allows producers to see how much water they are using. Producers can track the amounts used year to year and compare that with yield. Using flow meter data, when it is determined that irrigation water used exceeds the need, producers can reconsider the irrigation rate and frequency. Maximizing irrigation efficiency saves water and saves producers from paying for fertilizer and water that washes away without being used by crops.

• Conversion from gravity irrigation to center pivots increases the water application efficiency and reduces the likelihood of nitrate leaching.

• Installing programable control panels on pivots allows for precise application.

• Consider installing your own remote weather station and do not irrigate if rain is in the forecast.

• Use a soil probe to determine soil moisture levels and the need for irrigation. Sandy hilltops require a different rate and frequency of irrigation compared to heavier organic matter soils.



Considering the many other costs of farming, optimizing irrigation – and gaining the economic benefits that come with it – should be the goal of every irrigator.


Learn more in NebGuide G1904, at: https://cropwatch.unl.edu/documents/g1904.pdf

See the Lower Loup NRD’s Crop Water Use Report at: Crop Water Use Report