Extension Notes

by University of Missouri Extension Page

By: Valerie Tate, MU Extension Field Specialist in Agronomy

The amount of nitrogen needed to optimize corn yield differs significantly from one field to another, as well as within fields. Yield goal is the primary factor when recommending a nitrogen fertilizer rate. Using yield as a goal when determining nitrogen application rate generally optimizes the amount of nitrogen for corn growth when there are not any losses of nitrogen from the system.

Studies were conducted at the MU Graves-Chapple Extension and Education Center in northwest Missouri to evaluate both nitrogen rate and application timing. In the nitrogen rate study, urea with Agrotain was applied on April 26, 2022, to plots. Nitrogen application rates were 0, 60, 120, 160, 180, 240, and 300 pounds per acre. Pioneer 1359 hybrid was planted at a rate of 32,400 seeds per acre on April 30. Nitrogen products were surface applied onto no-till soybean residue.

Corn yield at the nitrogen application rate of 180 pounds per acre resulted in a yield of 197 bushels per acre. When nitrogen was applied at a rate of 240 pounds per acre it produced 207 bushels per acre. The additional 60 pounds of nitrogen fertilizer resulted in a 10 bushel per acre increase in yield. Increasing nitrogen rate to 300 pounds per acre produced 209 bushels per acre, only a two bushel per acre increase over the 240pound rate.

Many growers apply supplemental nitrogen into standing corn. A trial was conducted to compare nitrogen application rates and timings and the effect they have on yield. The treatments in this demonstration were: a check with no nitrogen added, 120 and 240-pound nitrogen preplant, split nitrogen application applied as a 120-pound preplant nitrogen application followed by top-dress application rates of 30, 60, 90 and 120 pounds at V-8 and V-16 corn growth stage. Preplant nitrogen applied was urea with Agrotain®. Pioneer PM1395 corn hybrid was planted at a rate of 32,400 seeds per acre on April 26.

Yield ranged from 195 bushels per acre for the 120 pounds preplant to 220 bushels per acre for the 240 pounds of nitrogen per acre applied preplant. There was a trend for supplemental nitrogen from 30 to 90 pounds to increase yield at both the V-8 and V16 application timing. The 120 pounds of nitrogen per acre applied preplant plus 90 pounds of nitrogen ap- plied at V-16 produced 218 bushels per acre. Growers will need to weigh their nitrogen costs, the cost for the application of additional nitrogen and the potential yields to calculate the most profitable practice for their operation.

Source: MU Graves Chapple Extension and Education Center 2022 Annual Report.

To see the full report, visit their website: https://extension.missouri.e du/programs/graves-chapple/