Deficiency is generally due to inadequate or ineffective N fertilization. When a deficiency occurs at this stage apply 40-50 pounds N per acre through the irrigation system or by conventional ground applicator as soon as possible. Avoid using rates higher than 50 pounds N per acre through the irrigation system.

Deficiency due to low soil P and/or inadequate P fertilization. Cool-wet growing conditions can induce P deficiency even when the soil test P level is medium or high. Correction generally occurs as the soil temperature increases if there is sufficient P available for normal growth. Corrective treatment is difficult to apply and may not be effective.

Deficiency due to low soil K and/or inadequate K fertilization. If K is low apply 30 pounds of K₂O per acre through the system. Rates should not exceed 30 pounds K₂O per acre. Use a soluble grade of muriate of potash as the K source. Soluble grade potash contains 60 - 62% K₂O and it can be readily dissolved and injected into the irrigation water.

Deficiency is not a common occurrence since the soil Ca level must be extremely low for Ca deficiency to occur. Usually low Ca is associated with low soil pH. Prevent deficiency by maintaining the soil pH at approximately 6.0. High Ca levels are due to a major element deficiency such as N,P, or K.

Deficiency occurs when the soil Mg level and/or soil pH is low. Deficiency can be induced by heavy applications of N and K fertilizer. If Mg is low in the tissue apply 5 pounds of Mg per acre as magnesium sulfate through the irrigation system or apply 0.30 to 0.40 pounds Mg per acre, as magnesium sulfate, in 20-25 gallons of water by ground applicator.

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 in the future by including a minimum of 10 pounds S per acre in the fertilizer. When S is low in the tissue, and no sulfur was applied in the preplant fertilizer, apply a minimum of 10 pounds S per acre using ammonium thiosulfate or other nitrogen-sulfur solutions.

Deficiency not likely to occur except on very sandy soils with a pH of 6.5 or higher or soils high in organic matter. Mn deficiency is more likely to occur when the soil is cool and wet under the conditions given above. The deficiency can be corrected by applying multiple foliar applications of 1 pound Mn per acre as manganese sulfate or 1/2 pound Mn per acre as manganese chelate in 20 to 25 gallons of water with a ground applicator, or by injecting 2 pounds Mn per acre as manganese sulfate through the irrigation system. Repeat the application in 10 to 14 days. High Mn is due to low soil pH and is frequently associated with low Ca and Mg levels.

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).

Deficiency is not likely to occur except on sandy low organic matter soils. If B is low in the tissue apply a total of 2 pounds of B per acre through the system. Split the application applying 1 pound per acre through the system as soon as possible and the remainder just prior to tasseling.

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

Deficiency is likely to occur on sandy soils that are low in organic matter (<1%) and soils that are near neutral in pH. Low Zn is also likely to occur under cool-wet growing conditions. A deficiency may be corrected by applying a foliar spray of Zn at a rate of 1/2 pound Zn per acre as zinc sulfate or zinc chelate in 20-25 gallons of water by ground application or 2 pounds Zn per acre as zinc sulfate or 1/2 pound Zn per acre as zinc chelate applied through the system. Zinc does not become toxic to corn plants until the Zn level exceeds 200 ppm.

High Al levels are due either to soil contamination (Fe will also be high), extremely low soil pH or if the soil has been wet for a long period of time. No immediate corrective treatment is recommended.

Deficiency not likely to occur.