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    Indiana Corn: Adjust Nitrogen Rate to Maximize Profit

    Corn fertilizer application. ©Debra L Ferguson Stock Photography

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

    Figure 1. Percent of maximum corn grain yield produced with different nitrogen rates for three groupings of regions in Indiana; northcentral (NC), northwest (NW), southcentral (SC), southeast (SE), southwest (SW), westcentral (WC), and sandy non-irrigated soils, northeast (NE) and eastcentral (EC), and central (C).

    Figure 1. Percent of maximum corn grain yield produced with different nitrogen rates for three groupings of regions in Indiana; northcentral (NC), northwest (NW), southcentral (SC), southeast (SE), southwest (SW), westcentral (WC), and sandy non-irrigated soils, northeast (NE) and eastcentral (EC), and central (C). Click Image to Enlarge

    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. here

    Table 1. Comparative costs per lb. of actual N for a range of 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
    $1,200 $0.73 $500 $0.89 $725 $1.13 $825 $0.90
    $1,250 $0.76 $525 $0.94 $750 $1.17 $850 $0.92
    $1,300 $0.79 $550 $0.98 $775 $1.21 $875 $0.95
    $1,350 $0.82 $575 $1.03 $800 $1.25 $900 $0.98
    $1,400 $0.85 $600 $1.07 $825 $1.29 $925 $1.01
    $1,450 $0.88 $625 $1.12 $850 $1.33 $950 $1.03
    $1,500 $0.91 $650 $1.16 $875 $1.37 $975 $1.06
    $1,550 $0.95 $675 $1.21 $900 $1.41 $1000 $1.09
    $1,600 $0.98 $700 $1.25 $925 $1.45 $1025 $1.11
    $1,650 $1.01 $725 $1.29 $950 $1.48 $1,050 $1.14
    $1,700 $1.04 $7570 $1.34 $975 $1.52 $1,075 $1.17
    $1,750 $1.07 $775 $1.38 $1000 $1.56 $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 $4.50 $5.00 $5.50 $6.00 $6.50 $7.00 $7.50
    $0.60 196 200 203 205 207 209 211
    $0.75 187 192 195 198 201 203 205
    $0.90 178 184 188 192 195 197 200
    $1.05 169 175 181 185 189 192 194
    $1.20 160 167 173 178 182 186 189
    $1.35 151 159 166 171 176 180 184
    $1.50 142 151 158 165 170 174 178
    $1.65 133 143 151 158 164 168 173
    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 $4.50 $5.00 $5.50 $6.00 $6.50 $7.00 $7.50
    $0.60 215 219 222 225 227 229 231
    $0.75 205 210 214 217 220 223 225
    $0.90 195 201 206 210 213 216 219
    $1.05 185 192 198 203 207 210 213
    $1.20 176 184 190 195 200 204 207
    $1.35 166 175 182 188 193 197 201
    $1.50 156 166 174 181 186 1891 195
    $1.65 146 1557 166 173 179 185 189
    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 $4.50 $5.00 $5.50 $6.00 $6.50 $7.00 $7.50
    $0.60 176 180 182 185 187 188 190
    $0.75 167 172 1575 178 181 183 185
    $0.90 159 164 168 172 175 177 180
    $1.05 150 156 161 165 169 172 174
    $1.20 141 148 154 159 163 166 169
    $1.35 132 140 147 152 157 160 164
    $1.50 124 132 139 145 150 155 159
    $1.65 115 124 132 139 144 149 153



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