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Agronomic Crops Network

Ohio State University Extension


Fertility Recommendations

A good nutrient management program is one of the keys to high yield corn production. Instituting best management techniques to ensure adequate nutrient availability throughout the growing season can pay real dividends at the end of the year and minimize the adverse effects of nutrient runoff and leaching on the environment. 


Timing and Sources 

Nitrogen fertilizer applications for corn production can be challenging to manage effectively. Fall application of nitrogen is not recommended, but if nitrogen is to be applied in the fall, make certain that soil temperatures are below 50 degrees Fahrenheit and that anhydrous ammonia is used. Do not apply nitrogen fertilizers that contain nitrate in the fall, the risk of loss is high due to leaching. Application of nitrogen in the spring is more efficient and less susceptible to loss. Nitrogen stabilizers may be used for early spring application, but the benefit of such compounds is inconsistent under certain growing conditions. Application of sidedress nitrogen is a good alternative to preplant applications of nitrogen. In-season applications move fertilization away from the busy planting period and are closer to actual crop uptake of nitrogen. Sidedressing also minimizes the risk of nitrogen loss especially on poorly drained, clay soils which are subject to denitrification and sandy soils which are susceptible to leaching. The main risk of in-season application is the possibility of delayed application due to wet conditions. 

When selecting a nitrogen source remember that a pound of nitrogen is a pound of nitrogen, make selections based on risk and cost. For example, it would be risky to apply urea to the surface of no-till ground due to the potential loss of nitrogen by volatilization. Surface dribble banding of liquid nitrogen or subsurface injection are better alternatives. This is not to say that urea is not a good source of nitrogen, but in this instance there are better options. Always consider the cost of the material as well as the field environment that will be encountered to get the most efficient use of fertilizer nitrogen. 


Current nitrogen recommendations for corn production are based on a simple economic model, the Maximum Return To Nitrogen (MRTN). In an area of variable grain prices and nitrogen fertilizer prices, this model strives to maximize farmer profitability, not maximize corn grain productivity. The MRTN takes into account a ‘typical’ yield response curve, the price of nitrogen fertilizer and the price of corn grain. A simple interface that allows users to generate nitrogen rate recommendations can be found at the following web address: . The background and justification for this approach is laid out in this regional publication:

Phosphorus and Potassium 

Application Methods 

Phosphorus and potassium are more straightforward than nitrogen when it comes to application methods. Phosphorus and potassium are not subject to the same loss mechanisms as nitrogen, thus application concerns are not as restrictive. The main loss mechanism for phosphorus is soil runoff. Utilization of conservation practices that minimize the risk of soil runoff to surface waters is adequate for good phosphorus management. Phosphorus and potassium can be applied either broadcast prior to planting or banded (near the row or over the row [pop-up]) as a starter when planting. If applying starter in a band 2 inches to the side and 2 inches below the seed, the total amount of salts applied (N + K2O) should not exceed 100 pounds per acre. If starter is applied with the seed (not recommended due to potential salt problems), the total salts (N + K2O) applied should not exceed 5 pounds per acre for low CEC soils or 8 pounds per acre for high CEC soils. The benefit of starter fertilizers increases when soil test levels and soil temperatures are low and when soil surface residues are high. Soils that have moderate to high levels of soil test phosphorus and potassium show little to no benefit from starter fertilizer. 


Little difference exists between commonly used forms of phosphorus and potassium with regard to nutrient uptake. Ortho- and poly-phosphate formulations perform equally well, even though the crop takes up the ortho- form (poly forms convert to ortho forms rapidly). It should be mentioned that if dry formulations of phosphorus are to be applied in contact with the seed, monoammonium phosphate (MAP) is a somewhat safer form of phosphorus to apply than diammonium phosphate (DAP). DAP produces more ammonia (NH3) which is toxic to germinating seeds. When banding MAP, DAP or ammonium polyphosphate (APP) do not exceed more than 40 pounds of nitrogen per acre. If soil test phosphorus and potassium are high on no- till soils, then only nitrogen should be applied as a starter, unless 40 to 60 pounds of nitrogen per acre has been applied preplant. 


Soil test levels below the critical value are considered deficient and warrant application of fertilizer (Table 4-14). Current recommendations for phosphorus and potassium are presented in Tables 4-15 and 4-16. Buildup and maintenance recommendations are designed to increase soil test levels to the critical value or maintain current soil test levels. Considering it takes between 8 to 20 pounds of P2O5 and 5 to 10 pounds of K2O (added or removed) to change the soil test level by one unit (depends largely upon soil texture), soil test levels above the critical value will be adequate for crop production for at least a few years (depending upon the soil test level). 

Table 4-14: Critical Levels for Soil-Test Phosphorus and Potassium.

P ppm (lb/ac)  K at CEC 
  5 10 20 30
  ---------ppm (lb/ac)--------- 
15 (30)1  88 (175)  100 (200)  125 (250)  150 (300) 

1 Values in parentheses are pounds per acre. 

Table 4-15: Phosphate (P2O5) Recommendations for Corn Using the Buildup and Maintenance Concept. 


Soil test ppm (lb/ac) 

Yield potential (bu/ac)

  100 120 140 160 180
  ------lb P2O5 per acre----

5 (10)1 

85 95 100 110 115
10 (20)  60 70 75 85 90
15-30 (30-60)2  35 45 50 60 65
35 (70)  20 20 25 30 35
40 (80)  0 0 0 0 0

1 Values in parentheses are pounds per acre.
2 Maintenance recommendations are given for this soil test range. 

Table 4-16: Potassium (K2O) Recommendations for Corn Using the Buildup and Maintenance Concept. 

Soil test K ppm (lb/ac)  Yield Potential (bu/ac) 
    100 120 140 160 180
    lb K2O per acre
  CEC  10 meq/100 g
25 (50)    160 165 170 175 180
50 (100)    120 125 135 140 145
75 (150)    85 90 95 100 105
100-130 (200-260)  45 50 60 65 70
140 (280)    25 25 30 30 35
150 (300)    0 0 0 0 0
  CEC  --------20 meq/100 g--------
25 (50)    195 200 210 215 220
50 (100)    145 150 160 165 170
75 (150)    95 100 110 115 120
125-155 (250-310)  45 50 60 65 70
165 (330)    25 25 30 35 35
175 (350)    0 0 0 0 0
  CEC  -------30 meq/100 g---------
25 (50)    235 240 245 250 255
50 (100)    170 175 185 190 195
75 (150)    110 115 120 125 130
150-180 (300-360)  45 50 60 65 70
190 (380)    25 25 30 30 35
200 (400)    0 0 0 0 0


Sulfur deficiencies are not common, but deficiencies are increasingly being reported, especially on sandier soils low in organic matter. Historically, sulfur was deposited in large quantities from atmospheric rainfall. However, emission standards on industrial activities have resulted in a sharp decrease in sulfur deposition from the atmosphere. As this trend continues, sulfur fertilization may become more important. Sulfur fertilization rates have not been established in Ohio. Corn grain removes a relatively low amount of sulfur: approximately 14 pounds of sulfur for 180 bushels per acre of corn. Accordingly, 20 to 40 pounds per acre of sulfur should be adequate for soils suspected of being deficient. Suitable sulfur fertilizers include: ammonium sulfate, ammonium thiosulfate and gypsum. 

For comprehensive information on corn fertilization and soil fertility management, consult OSU Extension Bulletin E-2567, Tri-State Fertilizer Recommendations for Corn, Soybeans, Wheat and Alfalfa, available online at: and

Crop Rotations 

The corn-soybean rotation is by far the most common cropping sequence used in Ohio. This crop rotation offers several advantages over growing either crop continuously. Benefits to growing corn in rotation with soybeans include more weed control options, fewer difficult weed problems, less disease and insect buildup, and less nitrogen immobilization which requires less fertilizer use. Corn grown following corn typically leads to a 2 to 19 percent reduction in yields compared to corn grown following soybeans. Recent work in the North Central Region has suggested that reduced soil nitrogen availability from high corn residue is a primary driver of yield reductions in continuous corn. Table 4-17 shows the influence of crop rotation on corn yields from 2003-2013 at two long-term research plots in Ohio. Continuous corn is the lowest yielding rotation, the corn-soybean rotation yields in the middle and the corn-meadow rotation yields the highest. The rotation effect is large at Hoytville but small at Wooster, showing that soil type and site location influences nitrogen dynamics and availability. The yield advantage to growing corn following soybean is often much more pronounced when drought occurs during the growing season. 

Table 4-17: Ten-Year Average (2003-2013) of Corn Grain Yield Grown in Varying Crop Rotations in the Long-Term Tillage Experiments in Ohio. The Chisel Tillage Treatment is Only Shown Here. 


  Hoytville Silty Clay Loam  Wooster Silt Loam 
Crop rotation  Corn Grain Yield (bu/ac) 
Continuous corn  144.8 183.2
Corn-soybean  160.5 183.7
Corn-meadow  175.2 202