High nitrogen fertilizer prices have led to changes in nutrient management programs to make them more affordable. Moving a portion of your planned nitrogen (N) application later into the growing season offers a lower risk of N loss to heavy rains and the opportunity to take advantage of any price reduction that may happen later in the season. Typically, local fertilizer dealers will discount their liquid N in late June and early July to reduce carryover supplies into the next season.
Fertigation, the process of applying fertilizer through irrigation, is a midseason option for maximizing savings and profitability. Liquid 28% N is the most common product for fertigation, but urea and micro-nutrient solutions are also available to meet crop needs, with the proper equipment. It often follows starter and side-dress applications as part of a three-step N plan.
Starter fertilizer applications allow quick access to nutrients to the newly germinated plants. Sidedress applications usually account for the greatest portion of the N budget, feeding the plant just prior to the rapid growth phase. Depending upon the equipment used, sidedressing can also aerate soil and improve water infiltration.
Work around the elements
Given the cool and wet early-to-late-spring soil conditions that many growers dealt with this year, irrigating producers may be wondering either how much N was lost or how much N to apply midseason. Kurt Steinke, Professor and Extension Specialist of Soil Fertility and Nutrient Management at Michigan State University, suggests that in irrigated corn scenarios with three or more planned N applications, applying the last 30 to 50 pounds with irrigation can be a solid strategy to help ensure that N will be available to the plant. Typically, V12 to V14 is the time frame that growers may want to apply those last units of N as there is some lag time between application and getting N into the plant.
For efficient use, applications need to be made prior to tasseling to ensure that the N applied is in an available form for the plant to uptake and use during early grain formation. A positive return on investment often exists up until the tasseling stage (VT) but rarely beyond, and it is impacted by the severity of prior N losses. If wet conditions prevented, delayed, or perhaps reduced an individual N application, apply rescue N as soon as possible. Remember that even in rescue N scenarios, rainfall or irrigation will still be required to get N into the plant.
Spring nitrogen losses from either denitrification, which occurs in low-lying areas with poor or no tile, or leaching, occurring in coarse-textured sandy soils, can be difficult to gauge. Producers need to have some idea on how much nitrate may have been present prior to the rainfall events or onset of saturated soil conditions. Under saturated conditions, denitrification losses may begin one to two days after saturation and can approach 5% of nitrate loss per day of saturation.
The degree and time length of saturation, soil and air temperatures, and amount of actual nitrate present will influence the amount of N lost. Under leaching conditions in sandier soils, the soil texture, cropping intensity, soil profile characteristics, volume and timing of precipitation, and rate, source, and method of N fertilization all influence N losses and can be difficult to quantify. Keep an eye out for visual deficiencies and utilize tissue testing. As soils dry out, some nitrate that moved deeper in the soil profile may move upwards through soil and closer to plant roots.
Stop the flow
The inherent risk of injecting fertilizer into a water system dictates the need for backflow protection. Some states require using chemigation valves for protecting both surface and ground water sources. Chemigation valves create an air gap in the pipeline downstream from the pump when it is shut down. The air gap breaks the suction created by water and allows it to retreat to groundwater or surface water. Chemigation valves should be included in almost all new irrigation pumping installations.
It is essential to know that the system applies water uniformly across the field. Center-pivot systems of good design and repair will have uniformity coefficients of greater than 85%. Many systems have uniformity coefficients in the 70% to 75% range, allowing the misapplication of a quarter of the water and fertilizer going through them. The “catch can” method is a simple, inexpensive option for evaluating irrigation system uniformity.
Some producers may choose to place pumps, chemigation backflow valves, and fertilizer storage at the pump site. This allows the same equipment to service multiple distribution systems but raises the risk of well contamination from fertilizer or chemical storage near the site. Using temporary tanks or delivering fertilizer when needed can help mitigate the contamination risks. Remove any leftover fertilizer at the end of the process.
In some situations, producers may choose to dribble or broadcast nitrogen on the field by air or tractor and use irrigation to incorporate the N fertilizer if dry weather follows. This technique is quick, requiring no irrigation equipment modification, but is dependent on the availability of aerial applicators or in-row, high-clearance application equipment.
As irrigators gain experience with fertigation, they are more likely to use it as part of their nitrogen plan. Fertigation reduces input losses, resulting in environmental and economic benefits. Local irrigation dealers and your state extension service can provide more information on how to implement fertigation on your farm.
The author is an irrigation educator for Purdue University and Michigan State University.
This article appeared in the August 2026 issue of Journal of Nutrient Management on pages 6 and 7.
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