December 10, 2020
- 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
|Soil Type||Hord silt loam|
- 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.
Figure 1. The yellow coloration of the corn leaves on the left (0 lb N/acre) indicate the beginning of a N deficiency compared to the dark green of the leaves to the right (60 lb N/acre).
UNDERSTANDING THE RESULTS
Figure 2. Average yield response to N application rates.
Figure 3. Pounds of N to produce one bushel of grain based on total available N per acre (including residual soil N).
- 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 an N application rate that maximizes the return on N investment should be taken into consideration when developing a cost-effective fertility program.