|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|
(Leaf below whorl)
Deficiency is due to inadequate or ineffective N fertilization. If nitrogen in the tissue is low prior to tasseling, apply 40-50 pounds of N per acre through the system. If N is low at tasseling, reduce the N rate to 30 pounds per acre. Excessively high N levels can result in induced S deficiency, unless adequate S levels arepresent.
Deficiency due to low soil P and/or inadequate P fertilization. Also, when corn is in the early stages of development (12-24) inches, low P can be due to cool wet weather conditions even on soils with medium or high soil test P levels. Generally, P levels in the tissue will increase to sufficient levels as the soil temperature increases. Corrective treatment is difficult to apply and is not effective.
(Leaf below whorl)
Deficiency due to low soil K and/or inadequate K fertilization. If potassium is low prior to tasseling, apply 30 pounds K2O per acre through the system. Do not exceed rates of 30 pounds K2O per acre because foliar burn may occur at higher rates. Use a soluble grade of muriate of potash as the K source. Soluble grade potash contains 60-62% K2O and can be readily dissolved and injected into the irrigation water. If potassium is low in the ear leaf tissue (at tasseling), no corrective treatment is recommended for the current crop. Often when the K level is high in the tissue, Mg levels in the tissue will be at the low end of the sufficiency range. Avoid excessively high applications of K to prevent the development of low Mg levels.
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. No corrective treatment is recommended for the current crop. Deficiency in succeeding crop can be avoided by liming to maintain soil pH at approximately 6.0. High Ca levels are due to a major element (N, P, or K) deficiency.
Deficiency occurs when soil Mg levels and/or soil pH is low. Deficiency can be also induced by heavy application of N and K fertilizer. If low Mg is detected prior to tasseling, apply 5 pounds of Mg per acre as magnesium sulfate through the irrigation system or apply 0.30 to 0.40 pounds of Mg per acre, as magnesium sulfate in 20-25 gallons of water by ground applicator. Corrective treatment at or after tasseling is not recommended.
(Leaf below whorl)
Low S may occur on sandy Coastal Plain soils where high analysis S-free fertilizers have been applied. Low S levels may be avoided by including a minimum of 10 pounds S per acre in the fertilizer. If the sulfur level in the tissue is low or if the N:S ratio exceeds 18:1, apply a minimum of 10 pounds S per acre through the irrigation system. Ammonium thiosulfate and nitrogen-sulfur solutions are preferred sources. For optimum corn yields the N:S ratio should be maintained between 10:1 and 15:1.
Deficiency not likely to occur except on very sandy soils or soils high in organic matter with a pH of 6.5 or higher. The deficiency can be corrected by injecting 2 pounds Mn per acre as manganese sulfate in the irrigation water. Application of Mn is not recommended after tasseling. High Mn is due to low soil pH and is frequently associated with Mg deficiency.
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. Boron deficiency can result in poor ear formation. If B is low at the leaf below the whorl stage, apply 2 pounds of B per acre through the system. Split the application, applying 1 pound per acre as soon as possible and the remainder just prior to tasseling. If B is low at the ear leaf stage and poor ear development is noted in the current crop, include B in future corn fertilizer programs at the rate of 2 pounds B per acre. No corrective treatment is recommended for current crop if B is low at the ear leaf stage. Boron may be high in soils where B fertilizer has been applied for other crops. Boron levels greater than 30 ppm are excessive. Since corn is quite sensitive to B, great care needs to be exercised when this element is included in fertilizer treatments.
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 which are 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 using 1/2 pound of Zn per acre as zinc sulfate or zinc chelate in 20 to 25 gallons of water by ground application or by injecting 2 pounds Zn per acre as zinc sulfate or 1/2 pound of Zn per acre zinc chelate through the system. Zinc does not become toxic to corn plants until the Zn level exceeds 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).
Deficiency not likely to occur.