Nitrogen Application Timings in No-Till Dryland Corn Production System
Nutifafa Adotey, Assistant Professor & Soil and Nutr. Magt Specialist and Ryan Blair, Extension Area Specialist III and County Standardized Trials Specialist - University of Tennessee
Introduction
Implementing appropriate N management practices such as the 4 R Nutrient Stewardship reduces N low, optimizes N uptake, improves productivity and overall profitability. Right timing of nitrogen application is one of the practices of the 4 R nutrient stewardship. It’s important to address three key questions in order to determine the optimal N application timing for dryland corn: (1) At what recommended rate should N fertilizer be split-applied, (2) What is the optimal split proportion if split application is required, and (3) what is the optimal growth stage if split application is required. In Tennessee, the current recommendation is to split apply a1/3 at planting (shortly after emergence) and sidedress the remaining N for dryland corn production. Since the update of the current recommendations for N management in dryland corn, there has been newer corn hybrids and the introduction of N management tools such as enhanced efficiency fertilizers. Information on the response of newer corn hybrids respond to nitrogen application is limited. In this study we (1) examined the optimal (1) rate to split-apply N (2) proportion to split-apply N and (3) timing for sidedress N application in non-irrigated corn.
Materials and Method
To evaluate the rate at farmers should split apply N fertilizer, trials were conducted at University of Tennessee (UT) Highland Rim Research and Education Center, Springfield and Research and Education Center at Milan from 2021 -2023. Three trials were established at each location. Each trial was set up as a randomized complete block design with 10 N fertilizer rate treatments (see table below) and replicated four times for a total of 40 plots. Individual plots consisted of 4 rows of corn plants with 30-inch row spacing and a length of 30 feet. At-planting and sidedress N were applied at emergence and between the V4 – V6 growth stage, respectively. The source of nitrogen was ANVOL-treated urea.
To evaluate the optimal proportion trials were conducted at University of Tennessee (UT) West TN Research and Education Center, Jackson in 2022 and 2023. Trial was set up as a randomized complete block design with 6 N fertilizer proportions (see table below) and replicated four times. A control plot, with no nitrogen was included in the trial. Individual plots consisted of 4 rows of corn plants with 30-inch row spacing and a length of 30 feet. The source of nitrogen was ANVOL-treated urea.
To evaluate the optimal timing for sidedress N, trials were conducted at University of Tennessee (UT) West TN Research and Education Center, Jackson in 2022 and 2023. Trial was set up as a randomized complete block design with 4 timing for sidedress N (see table below) and replicated four times. A control plot, with no nitrogen was included in the trial. Individual plots consisted of 4 rows of corn plants with 30-inch row spacing and a length of 30 feet. The source of nitrogen was ANVOL-treated urea.
Results and Discussion
Optimal split rate
Only 13 site-years data out of 18 site-year is presented and discussed in this report due to in-season drought in 2022 and germination issues in 2023. Due to the drought, the average yield across trial for each year is presented and discussed. In the years, the average grain yields from split-applications (grey bars) were significantly than the single-applications at the 120 lb N/A and beyond except in 2023, where there was no significant yield difference at the 180 lb N/A rates and the rates beyond for split-application. This indicates that the optimal split rate is 120 lb N/A and beyond. Regardless of the year, split application of 180 lb N/A was similar to single application of 300 lb N/A at planting.
Optimal split proportion
In 2022, there was significant differences in the split proportions, with the highest yield occurring at the 60/120 lb N/A. In 2022, there was at least 15% yield penalty when 2/3 (120 lb N/A) or more of the total recommended N was applied at planting. In contrast, there was no difference between the split proportion in 2023, where yield penalty was insignificant. Nonetheless, the highest yield occurred at the 60/120 lb N/A. The optimal spilt proportion of N fertilizers was 60/120 lb N/A, so If split application is recommended, then split apply 1/3 at planting and sidedress the remaining N.
Optimal timing for sidedress N
In 2022, the highest yield was observed when sidedress N was applied at V8, which was similar to the other timings except V14. A 15% yield reduction was observed when N was delayed until the V14. In 2023, the highest yield was observed when sidedress N was applied at V8, which was similar to on V6 but significantly higher than V10 and V14. A 7 and 40% yield reduction were observed when N was delayed until the V10 and V14, respectively.
Results from these trials demonstrates that split application is recommended when N rates are greater than 120 lb N/A. If split application is recommended, then split apply 1/3 at planting and sidedress the remaining around V6 growth stage.
Further reading
