Deficiency generally due to inadequate or ineffective N fertilization. When occurring at this stage, apply N fertilizer as soon as possible at a rate of 50 to 75 pounds N per acre. The method of application should place N within easy reach of the plant roots. Shallow placement is more desirable than deep placement.

Deficiency may be due to low soil P and/or inadequate P fertilization. Cool wet weather conditions can also induce P deficiency even when the soil test level is medium or high. If the latter condition prevails, deficiency symptoms will disappear and the P content of the plants will increase as soil temperature increases. 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 in the tissue and the soil test K level is low or medium, sidedress with 50 to 75 pounds K₂O per acre. If the soil test K level is high do not apply additional K₂O. Avoid excessive applications as they could induce Mg deficiency.

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. Deficiency can be corrected by liming. 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 also be induced by cool-wet growing conditions as well as by heavy applications of N and K fertilizers. If Mg in the tissue is low, broadcast 25 pounds Mg per acre (Sul-Po-Mag, K-Mag, and magnesium sulfates) or apply a foliar application using 0.30 to 0.40 pounds of Mg per acre in 20 to 25 gallons of water. Repeat the foliar application in 10 to 14 days if symptoms persist. If the soil pH is less than 5.5 and plant Mg is low, a broadcast application of dolomitic limestone at the rate of 1000 pounds per acre along with a foliar application of Mg at the rate of 0.3 pounds Mg per acre in 20 to 25 gallons of water may be effective in controlling Mg deficiency.

Low S may occur on sandy Coastal Plain soils where high analysis S-free fertilizers have been applied for several years. Low S levels may be avoided by including a minimum of 10 pounds S per acre in the fertilizer. When S is low in tissue, apply a minimum of 10 pounds S per acre, preferably with the sidedress N application.

Deficiency is 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 a foliar application of 1 to 2 pounds Mn per acre as manganese sulfate or 1/2 to 1 pound Mn per acre as manganese chelate in 20 to 25 gallons of water. If deficiency symptoms are still evident in 10 to 14 days repeat the application. High Mn is due to low soil pH and frequently associated with Mg deficiency. (See Mg discussion above).

Deficiency 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 very sandy low organic matter soils. If these soil conditions exist and B in the tissue is low, apply a foliar application of B using 1/4 pound of actual B per acre in 20-25 gallons of water. On heavier soils no corrective treatment is recommended at this stage of growth. Boron may be high on soils where B fertilizer has been applied for other crops. Boron levels in excess of 30 ppm are excessive.

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

Deficiency likely to occur on sandy soils, low in organic matter (<1%), and soils that are near neutral in pH. A deficiency may be corrected by a foliar application of Zn at a rate of 1/2 pound Zn per acre as zinc sulfate or zinc chelate in 20 to 25 gallons of water. Zinc does not become toxic to corn 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. There is no corrective treatment for current crop when Al is high.

Deficiency not likely to occur.