December 10, 2020
TRIAL OBJECTIVE
- 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 environmental impacts.
- The objective of this study was to evaluate the response of corn products to different N rates.
RESEARCH SITE DETAILS
Location | Gothenburg, NE | ||
Soil Type | Hord silt loam | ||
Previous Crop |
Corn | ||
Tillage Type |
No tillage |
Planting Date | 4/3/20 | ||
Harvest Date | 11/4/20 | ||
Potential Yield (bu/acre) |
250 | ||
Seeding Rate (seeds/acre) |
36K |
- 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).
KEY LEARNINGS
- 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 an N application rate that maximizes the return on N investment should be taken into consideration when developing a cost-effective fertility program.
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