Corn Response to Nitrogen Rates
• The optimum nitrogen (N) rate for corn can be difficult to determine. Inadequate N can cause a noticeable
reduction in yield while excess, unused N reduces the return on N investment and can have negative
• The objective of this study was to evaluate the response of corn products to different N rates.
Research Site Details
• The study was set up as a split-plot design with four replications.
• Four different relative maturity (RM) corn products (109RM, 111RM, 112RM, and 114RM) were evaluated under
six different N rates (0, 60, 120, 180, 240, and 300 lb N/acre). Nitrogen was applied with 360 Y-DROP® fertilizer
tube attachments at the V6 growth stage on 6/18/20.
• Weeds were uniformly controlled, and no insecticides or fungicides were applied.
• Grain weight and grain moisture were collected to calculate yield.
Understanding the Results
• There was no N rate by corn product interaction, so data were averaged across corn products.
• The previous crop was corn which depleted the soil profile of N and other nutrients. The residual N in the top two
feet of soil is shown in Table 1.
• As N rate increased, yield increased until it reached a maximum at 240 lb N/acre (Figure 2).
• The amount of N to produce on bushel of grain increased as the applied N rate increased. More N was needed
to produce one bushel of grain at the higher N rates compared to the lower N rates (Figure 3).
• As N fertilizer cost increased, the return on N investment decreased. For this trial, the largest return on N
investment was at the 60 lb N/acre rate and the lowest return was at the 300 lb N/acre rate (Table 2).
• The law of diminishing returns is illustrated in this study with more value observed from the first 60 lb N/acre
applied compared to the last 60 lb N/acre.
• Nitrogen application rates are a key factor in maximizing yield. Determining residual N in the soil in combination
with a N application rate that maximizes return on N investment should be taken into consideration when
developing a cost-effective fertility program.
The information discussed in this report is from a single site, replicated demonstration. This informational piece is designed to report the results of this demonstration and is not
intended to infer any confirmed trends. Please use this information accordingly.
Performance may vary, from location to location and from year to year, as local growing, soil and weather conditions may vary. Growers should evaluate data from multiple
locations and years whenever possible and should consider the impacts of these conditions on the grower’s fields.
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