Maximizing Corn Ear Size and Yield with Zinc and Molybdenum
Ear Size and Yield Potential Begins Early
Several factors limit the yield potential of corn. One of these factors is the size of the ear, or more precisely the number and size of the kernels on the ear. The number of potential kernels that an ear can have is determined both by the length of the ear and the number of kernels around the ear. The more kernels available, the greater the potential for higher yields.
The number of kernels on an ear is determined early in the corn plant’s life, approximately at the V5-V6 stage of development. V5-V6 means when the 5th and 6th true leaves emerge from the whorl. The crop may be only about a foot or so tall at this time.
During early growth, the corn crop needs good nutrition for active growth. When soil tests are taken, many growers and agronomist look at the results to determine the need for nitrogen (N), phosphorus (P) and potassium (K). These nutrients are vitally important to the overall growth of the crop and its yield. However, during the formation of the corn kernels and the ear size, two other essential plant nutrients are required to maximize corn yields. These nutrients are zinc and molybdenum.
Zinc and Molybdenum Increases Ear Size
Corn needs zinc and molybdenum to make the growth regulator indoleacetic acid (IAA). IAA controls the number and size of the kernels that grow on each ear, as well as the number of ears that can form on the corn plant. When IAA is low, the ears are smaller and have fewer kernels. Thus a zinc or molybdenum deficiency can cause a reduction in corn yield by limiting available IAA.
Since the ears and kernels formed at the V5-V6 stage of plant development, zinc and molybdenum needs to be available to the corn crop by V5. Applying zinc and molybdenum after V6 provides no benefit to increasing the ear size. Applying it then is analogous to the old saying “closing the barn door after the cow gets out.” It may be necessary or beneficial to apply zinc and molybdenum to the corn after V6 for better nitrogen utilization and photosynthesis, but these nutrients are critical early in the corn crop’s life cycle to ensure the size of the corn ear.
How and When to Apply Zinc and Molybdenum
To meet this early need for these nutrients, zinc is often applied to corn in-furrow with starter fertilizers, or over the top of the crop by V5, as with herbicides or other chemicals. Chelated forms of zinc are the most effective in getting zinc into the plant. AgriGuardian™ provides two forms of zinc, both contain 9% chelated zinc. When zinc is used in-furrow with starter fertilizer, chelated AgriGuardian EDTA Zinc™ (ethylene diaminetetracetic acid) is most commonly used since it can tolerate higher pH that is often found in starter fertilizers. For foliar application, AgriGuardian Zinc™ is preferred. It is a sugar-based chelated liquid zinc fertilizer that can quickly penetrate the waxy surface layer of the leaves. Also, once inside the plant, the sugar-bound nutrient can move quickly to the sites where the nutrient is needed. With either product or application method, the rate of application is typically 16-32 oz. per acre, and is applied when zinc levels in the soil or plant are low, or in question.
Molybdenum is also needed for the formation of IAA. Smaller amounts of molybdenum are needed, but it is just as essential for ear development as is zinc. AgriGuardian Moly™ is typically applied with zinc to ensure they are both available for the formation of IAA. Do a soil test to determine if molybdenum is low, but it is very common to find it deficient in soils. Also, molybdenum in the soil is not readily available to crops when the soil is pH 5.5 or lower. Rates of application of AgriGuardian Moly™ are typically 4 oz. per acre. Besides being needed for the formation of IAA, molybdenum is required for the plant to use nitrate nitrogen taken up from the soil. When molybdenum is low in the soil, an additional 4 oz. application may be needed midseason to get the maximum benefit of nitrogen in the soil.
Not Just for Corn
In addition to corn, the same processes (and thus the need for zinc and molybdenum) affect the head size and number of grains in wheat, oats, barley, and virtually all other grain crops. Thus nutrients levels and early application of zinc and molybdenum need to be considered with these crops as well.
Contact your local AgriGuardian™ distributor for more information on products, how to maximize your ear size, and increase overall yield.
