By Lyndon Kelley
High nitrogen (N) fertilizer prices have many producers looking to change their nitrogen management program. Moving a portion of your planned N application into late June or even early July offers a lower risk of N loss to heavy rains and the opportunity to take advantage of any price reduction that may happen through May and June. Typically, local fertilizer dealers will discount their liquid nitrogen in late June and early July to reduce carryover supplies into the next season.
Irrigated production has the advantage of fertigation as an option in nitrogen management. Fertigation is the process of applying fertilizer through irrigation water. Liquid 28% nitrogen is the most common product for fertigation, but urea and micro-nutrient solutions are also available to meet crop nutrient needs, with proper equipment.
Fertigation is often the last step in a three split nitrogen management plan, following starter and side dress applications. Starter allows quick access to nutrients to the newly germinated plants. Side dress applications usually account for the greatest portion of N budget, feeding the plant just prior to the rapid growth phase. Depending upon the equipment used, side-dressing can also aerate soil and improve water infiltration. Fertigation makes up the remainder of the budget supplying nitrogen to the crop just prior to tassel emergence. For efficient use, nitrogen applications need to be made prior to tasseling to ensure that the nitrogen applied is in an available form for the plant to uptake and use during early grain formation.
From a management standpoint, fertigation allows producers the opportunity to evaluate crop stands, calculate N losses due to wet conditions or heavy rains, and account for the current market situation. This gives producers more control of their nitrogen plan since they have a longer application window, allowing them to meet the crops’ needs and maximize profitability.
As an example, let’s say a producer has a 270-bushel yield goal on an irrigated field that calls for 230 pounds of nitrogen in their plan. At planting, they apply 30 pounds of nitrogen, followed by 120 pounds applied at cultivation in early June. This leaves a nitrogen need of 80 pounds. The producer decides to apply the remaining 80 pounds split into two 40-pound applications through the irrigation. We get about 3.1 pounds of actual nitrogen for each gallon of 28% N applied. The producer calculates that they need to apply just short of 13 gallons per acre. Knowing that their system irrigates 2 acres per hour at a given setting, the producer calculates that they need to inject 26 gallons of the fertilizer per hour.
Source : msu.edu