Timing of Nitrogen Application

Trial Overview

  • There is considerable interest in applying nitrogen (N) later in the growing season; therefore, farmers and agronomists want to know when is the best time to sidedress N in a later-season application.
  • Because N is a major and required investment in corn production, knowing when corn plants are most responsive to an application of N can help farmers determine the application time for the best return on their investment. 

Research Objective

  • To compare the effectiveness of different N application times during the growing season.
Soil Type
Previous Crop
Tillage Type
Planting Date
Harvest Date
Potential Yield
Planting Rate
Monmouth, IL
Silt Loam
290 bu/acre
36,000 seeds/acre

Site Notes:

A 114 RM SmartStax® RIB Complete® corn blend product was utilized in the trial.Nitrogen in the form of 32% UAN (32-0-0) was used as the N source.80 lbs/acre of N was applied before planting and incorporated.Nitrogen was sidedressed with a high-clearance sprayer using 360 Y-DROP® at an application rate of 100 lbs/acre with a urease inhibitor at three growth stages:
- V4 (4 leaf collars) on 6/09/17
- V8 (8 leaf collars) on 6/19/17
- V12 (12 leaf collars) on 7/05/17The trial consisted of 3 replications.Data from 2016 was added for supporting information. 

Understanding the Results

Figure 1. Average yield (bu/acre) response to nitrogen application timing in 2017 at Monmouth, IL (3 replications).
  • Individual corn products may respond differently to the timing of an application of N.
  • The cost to potentially obtain greater yields, based on the timing of an application of N, may not be economically feasible when all costs are considered. 
  • The ideal timing of a later-season application could change yearly because of weather and environmental challenges.
  • In 2016, the V8 application demonstrated a larger response (2016 response: V4 = 235.7, V8 = 240.4, and V12 = 228.7).2 However, the average differences for the combination of 2016 and 2017 were minimal (Figure 2).

What Does This Mean for Your Farm

  • Nitrogen applications later in the growing season have the potential to improve yields and reduce the potential for N loss through leaching and nitrification.1 
  • Environmental conditions and the costs associated with N applications should be considered when making a N plan for each field.
  • Use of 360 Y-DROP® for later growth season N applications can allow for greater flexibility in the timing of the application and use in taller corn.