Corn Response to Nitrogen Rates

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.

image 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

image
image Figure 2. Average yield response to N application rates.
image Figure 3. Pounds of N to produce one bushel of grain based on total available N per acre (including residual soil N).
image
  • 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.
 
1011_R6_20 

 

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