Adjust Nitrogen Rate to Maximize Profit in Corn

Corn yield response to increasing nitrogen (N) rate follows the Law of Diminishing Returns as higher and higher increments of N are applied, the increase in grain yield becomes smaller and smaller (Figure 1). Eventually, maximum yield occurs and applying more N does not increase yield any further.

Interestingly, maximum yield regarding N fertilization does not produce the maximum profit. Profit from N application is maximized when the value of additional grain produced is just greater than the cost of additional N. Beyond that rate of N, profit declines because the cost of N is more than the value of additional grain produced.

We recommend that farmers select the rate of N to be applied based on the cost of N and the expected value of grain. Currently, the cost of N is historically high, nearly $1 per pound of N from anhydrous ammonia to more than $1 per pound for liquid N. Use Table 1 to find your cost of N per pound from the per ton cost. Grain prices are also relatively high and some expect them to increase in the future.

To obtain the profitoptimizing N rate recommendation for your N cost and expected grain price use the Table for the appropriate regional grouping. For example, assuming N at 1$ per pound and corn at $6.50 per bushel, the optimum profitable N rate for corn after soybeans for the three IN regional groupings would be 191, 209, and 171 pounds of N per acre for finetextured soils in central (Table 2), northeast and eastcentral (Table 3), and the remainder of Indiana including sandy nonirrigated soils (Table 4). At these profitoptimizing rates the reduction in yield would only be 12%, compared to fertilizing for maximum yield.

For more information about how these recommendations were developed and other N management practices that can increase profit, download this online summary:
Jim Camberato, RL (Bob) Nielsen, and Dan Quinn. 2022. Nitrogen Management Guidelines for Corn in Indiana. Purdue University, Agronomy Dept., Applied Crop Research Update. https://www.agry.purdue.edu/ext/corn/news/timeless/NitrogenMgmt.pdf [URL accessed Mar 2022]

 

Table 1. Comparative costs per lb. of actual N for varying costs per ton of product for four fertilizer sources of N commonly used in Indiana.
Anhydrous N cost/lb 28% UAN N cost/lb 32% UAN N cost/lb Urea N cost/lb
$1,050 $0.64 $550 $0.98 $625 $0.98 $550 $0.60
$1,100 $0.67 $575 $1.03 $650 $1.02 $600 $0.65
$1,150 $0.70 $600 $1.07 $675 $1.05 $650 $0.71
$1,200 $0.73 $625 $1.12 $700 $1.09 $700 $0.76
$1,250 $0.76 $650 $1.16 $725 $1.13 $750 $0.82
$1,300 $0.79 $675 $1.21 $750 $1.17 $800 $0.87
$1,350 $0.82 $700 $1.25 $775 $1.21 $850 $0.92
$1,400 $0.85 $725 $1.29 $800 $1.25 $900 $0.98
$1,450 $0.88 $750 $1.34 $825 $1.29 $950 $1.03
$1,500 $0.91 $775 $1.38 $850 $1.33 $1,000 $1.09
$1,550 $0.95 $800 $1.43 $875 $1.37 $1,050 $1.14
$1,600 $0.98 $825 $1.47 $900 $1.41 $1,100 $1.20

 

Table 2. Range of economic optimum N rate (EONR) values (lbs applied N/ac) for corn following soybean in central Indiana on medium- and fine-textured soils as influenced by nitrogen cost per lb N (Table 1) and grain price per bushel. The underlying yield response data are from 23 field scale trials conducted from 2006 to date. The average agronomic optimum N rate for this region of Indiana is approximately 232 lbs N/ac. These rates assume N management practices that minimize the risk of N loss prior to plant uptake.
Central Indiana
Grain Price
N cost $4.00 $4.50 $5.00 $5.50 $6.00 $6.50 $7.00
$0.90 171 178 184 188 192 195 197
$1.00 165 172 178 183 1887 191 194
$1.10 158 166 173 179 183 186 190
$1.20 151 160 167 173 178 182 186
$1.30 144 154 162 168 174 178 182
$1.40 138 148 156 163 169 174 178
$1.50 131 142 151 158 165 170 174
$1.60 124 136 146 154 160 166 170

 

Table 3. Range of economic optimum N rate (EONR) values (lbs applied N/ac) for corn following soybean in northeast and eastcentral Indiana on medium- and fine-textured soils as influenced by nitrogen cost per lb N (Table 1) and grain price per bushel. The underlying yield response data are from 37 field scale trials conducted from 2006 to date. The average agronomic optimum N rate for these regions of Indiana is approximately 254 lbs N/ac. These rates assume N management practices that minimize the risk of N loss prior to plant uptake.
Northeast & Eastcentral Indiana
Grain Price
N cost $4.00 $4.50 $5.00 $5.50 $6.00 $6.50 $7.00
$0.90 188 195 201 206 210 213 216
$1.00 181 189 195 201 205 209 212
$1.10 173 182 189 195 200 204 208
$1.20 166 176 184 190 195 200 204
$1.30 158 169 178 185 190 195 200
$1.40 151 163 172 179 185 191 195
$1.50 144 156 166 174 181 186 191
$1.60 136 149 160 168 176 182 187

 

Table 4. Range of economic optimum N rate (EONR) values (lbs applied N/ac) for corn following soybean in northcentral, northwest, southcentral, southeast, southwest, and westcentral Indiana on medium- and fine-textured soils, plus sandy non-irrigated areas throughout the state as influenced by nitrogen cost per lb N (Table 1) and grain price per bushel. The underlying yield response data are from 106 field scale trials conducted from 2006 to date. The average agronomic optimum N rate for these regions of Indiana is approximately 211 lbs N/ac. These rates assume N management practices that minimize the risk of N loss prior to plant uptake.
Northcentral, Northeast, Southcentral, Southeast, Southwest, Westcentral +Sandy Non-irrigated Areas of Indiana
Grain Price
N cost $4.00 $4.50 $5.00 $5.50 $6.00 $6.50 $7.00
$0.90 152 159 164 168 172 175 177
$1.00 145 153 159 163 167 171 174
$1.10 139 147 153 159 163 167 170
$1.20 132 141 148 154 159 163 166
$1.30 126 135 143 149 154 159 162
$1.40 119 129 138 144 150 155 159
$1.50 113 124 132 139 145 150 155
$1.60 106 118 127 135 141 146 151

 

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