Plant Part and Time: Leaf below the whorl prior to tasseling.
Ear leaf at tasseling collected before the silks turn brown.
Element and Sufficiency Range Interpretation and Recommendations
Nitrogen (N)
(Leaf below whorl)
(Ear leaf)

Deficiency due to inadequate or ineffective N fertilization. When occurring prior to tasseling sidedress with 50-75 pounds N per acre. When occurring at silking, no corrective treatment is recommended.

Phosphorus (P)

Deficiency due to low soil P and/or inadequate P fertilization. Corrective treatment not recommended. Soil test and follow soil test recommendation for next crop.

Potassium (K)
(Leaf below whorl)
(Ear leaf)

Deficiency due to low soil K and/or inadequate K fertilization. Corrective treatment not recommended. If K in the tissue is high, it is generally due to excessive K fertilization. Soil test and follow soil test recommendation. Avoid large applications of K fertilizer to prevent a possible inducement of Mg deficiency. When plant is Mg deficient, the K level is usually high.

Calcium (Ca)

Deficiency is not likely to occur as the soil Ca level must be extremely low for a deficiency to occur. Usually low soil Ca is associated with low soil pH. Deficiency can be corrected by liming to maintain soil pH at approximately 6.0. High Ca levels are due to a major element (N, P, or K) deficiency.

Magnesium (Mg)

Deficiency occurs when the soil Mg level and/or soil pH is low and when prolonged cool-wet growing conditions prevail early in the season. Deficiency can also be induced by heavy applications of N and K fertilizer. Corrective treatment may be ineffective unless applied well in advance of tasseling. If low Mg is detected, apply a foliar application of Mg using 0.30 to 0.40 pounds Mg per acre as magnesium sulfate in 20-25 gallons of water or if the soil pH is above 5.4 and the soil Mg level is low apply 25 pounds of Mg per acre. If the soil pH is less than 5.4 corrective treatment is not recommended.

Sulfur (S)
(Leaf below whorl)
(Ear leaf)

Low S may occur on sandy Coastal Plain soils where high analysis S-free fertilizers have been applied for several years. Avoid low S levels by including a minimum of 10 pounds S per acre in the fertilizer. If sidedress nitrogen has not been applied, use a nitrogen sulfur combination material that contains 3 to 5% S as the nitrogen source. If sidedress N has been applied, apply a foliar application of S using 10 to 20 pounds of ammonium sulfate or 1/2 to 1 gallon of ammonium thiosulfate in 30 to 50 gallons of water per acre. The latter material may cause some foliar burn, but should not adversely affect yields. For optimum corn yields the N:S ratio should be maintained between 10:1 to 15:1.

Manganese (Mn)
15-300 ppm

Deficiency is not likely to occur except on sandy soils or soils high in organic matter with a pH of 6.5 or higher. The deficiency can be corrected by a foliar application of 1 to 2 pounds Mn per acre as manganese sulfate or 1/2 to 1.0 pound Mn per acre as manganese chelate in 20 to 25 gallons of water. High Mn is due to low soil pH and frequently associated with Mg deficiency (see Mg discussion above).

Iron (Fe)
30-200 ppm

Deficiency is not likely to occur. High Fe test results normally indicate soil or dust contamination. An accurate Fe determination can only be made with washed leaves (See section - Washing to Remove Contaminates).

Boron (B)
4-25 ppm

Deficiency not likely to occur, except on very sandy low organic matter soils. Boron deficiency generally results in poor ear formation. If low leaf B and poor ear development are noted, B should be included in future corn fertilizer programs at the rate of 1 pound B per acre. Boron may be high in soils where B fertilizer has been applied for other crops. Boron levels in excess of 30 ppm are excessive. Since corn is quite sensitive to B, great care needs to be followed when this element is included in fertilizer treatments.

Copper (Cu)
3-15 ppm

Deficiency not likely to occur. High Cu levels may occur when soils have been treated with poultry or other animal manures.

Zinc (Zn)
15-60 ppm

Deficiency may occur on sandy soils low in organic matter (<1%) and soils that are near neutral in pH. A deficiency can be corrected by applying a foliar application of zinc at rates of 1/2 pound Zn per acre as zinc sulfate or zinc chelate in 20 to 25 gallons of water.

Aluminum (Al)
0-200 ppm

High Al levels occur when the soil is wet for long periods or the soil pH is extremely low. However, Al does not easily enter the plant after about 3 weeks after emergence. High Al may also be due to soil or dust contamination in which case Fe is also usually high (See Fe discussion above).

Molybdenum (Mo)
0.1-3.0 ppm

Deficiency not likely to occur.