1. Current N Fertilization Strategy for Corn in Missouri Newell Kitchen Cropping Systems and Water Quality Research Unit Columbia, Missouri USDA-ARS

2. Major Soil Regions in Missouri

3. Missouri Corn Nitrogen Requirement (NR): University of Missouri: NR (lbs/A) = POP x 4 + 0.9 x YG – MN Where: POP is the plant population in 1000s YG is expected yield in bu/A MN is the expected N mineralization from SOM University of Missouri: NR (lbs/A) = POP x 4 + 0.9 x YG – MN Where: POP is the plant population in 1000s YG is expected yield in bu/A MN is the expected N mineralization from SOM Table 2. Nitrogen rate adjustments 1. An example calculation for nitrogen requirement on corn: Table 2. Nitrogen rate adjustments 1. An example calculation for nitrogen requirement on corn:

4. Table 2. Nitrogen rate adjustments 1. An example calculation for nitrogen requirement on corn: Table 2. Nitrogen rate adjustments 1. An example calculation for nitrogen requirement on corn: Soil texture Cation exchange capacity (me/100 g.) Organic matter (%) Cool-season crops (lbs. N/A) Warm-season crops (lbs. N/A) Sands — sandy loam less than 100.5 1.0 1.5 10 20 30 20 40 60 Silt loams — loam 10 to 182.0 3.0 4.0 20 30 40 40 60 80 Clay loams — clays greater than 182.0 3.0 4.0 5.0 10 15 20 25 20 30 40 50 1 Based on soil texture, organic matter and time of major growth. Nitrogen rate adjustment based upon soil texture, organic matter, and time of major crop Nitrogen rate adjustment based upon soil texture, organic matter, and time of major crop

5. Missouri Corn Nitrogen Requirement (NR): MFA: NR (lbs/A) = 1.5 x YG - MN - PCA Where: YG is expected yield in bu/A MN is the expected N mineralization from SOM PCA is the previous crop addition (ex. 20 for soybean) A CEC adjustment within MN is an attempt to correct for N loss associated with leaching in low CEC soils and denitrification in high CEC soils. A CEC of 10 (silt loam) was set as the pivot point. MFA: NR (lbs/A) = 1.5 x YG - MN - PCA Where: YG is expected yield in bu/A MN is the expected N mineralization from SOM PCA is the previous crop addition (ex. 20 for soybean) A CEC adjustment within MN is an attempt to correct for N loss associated with leaching in low CEC soils and denitrification in high CEC soils. A CEC of 10 (silt loam) was set as the pivot point. Table 2. Nitrogen rate adjustments 1. An example calculation for nitrogen requirement on corn: Table 2. Nitrogen rate adjustments 1. An example calculation for nitrogen requirement on corn:

6. MFA’s Previous Crop N Credit for common crops in the Lower Midwest Previous CropNitrogen Credit (lbs./acre) Soybeans 10 Winter Wheat-10 Corn-10 Milo-20 Cotton-10 Rice-20 Alfalfa (1/2 stand) 40 Previous CropNitrogen Credit (lbs./acre) Soybeans 10 Winter Wheat-10 Corn-10 Milo-20 Cotton-10 Rice-20 Alfalfa (1/2 stand) 40

7. Given: A soil test CEC = 10, O.M. = 2.0, previous crop = corn, plant population = 28,000. What are the MFA and University of Missouri N Recommendations for a yield goal of 160 bu/A corn? Exactly the same: 200 lbs N/A

8. Other Important N BMPs in Missouri For river bottom soils and irrigated fields, farmers are encouraged to side-dress the majority of NFor river bottom soils and irrigated fields, farmers are encouraged to side-dress the majority of N -about 90% of “boot-heel” farmers side-dress For river bottom soils and irrigated fields, farmers are encouraged to side-dress the majority of NFor river bottom soils and irrigated fields, farmers are encouraged to side-dress the majority of N -about 90% of “boot-heel” farmers side-dress

9. The preplant N test is advocated under certain conditions: on fields that have received manure anytime since the previous summer.on fields that have received manure anytime since the previous summer. on fields that have a history of heavy manure applications.on fields that have a history of heavy manure applications. following a drought year on fields with a high potential for carry over for fertilizer N.following a drought year on fields with a high potential for carry over for fertilizer N. following fall and early spring fertilizer applications where excessive rainfall may have caused losses of fertilizer N.following fall and early spring fertilizer applications where excessive rainfall may have caused losses of fertilizer N. The preplant N test is advocated under certain conditions: on fields that have received manure anytime since the previous summer.on fields that have received manure anytime since the previous summer. on fields that have a history of heavy manure applications.on fields that have a history of heavy manure applications. following a drought year on fields with a high potential for carry over for fertilizer N.following a drought year on fields with a high potential for carry over for fertilizer N. following fall and early spring fertilizer applications where excessive rainfall may have caused losses of fertilizer N.following fall and early spring fertilizer applications where excessive rainfall may have caused losses of fertilizer N. Other Important N BMPs in Missouri

10. Ammonium nitrate is the preferred source of nitrogen in no-till when injection is not possible and the material must be surface broadcast. Nitrogen source Corn yield 1 Ammonium nitrate (34-0-0) 149 Urea (46-0-0) 142 UAN solution (32-0-0) 132 1 Average across 8 site years in Missouri Other Important N BMPs in Missouri