When you hear the word "micro," what comes to mind? Do you immediately think "inconsequential," "insignificant" or "nonessential"? If so, you may assume that micronutrients are an optional component of your plant nutrition program. But that's not the case. Micronutrients are needed in smaller quantities compared to macronutrients, but their importance on plant nutrition for your corn and soybean crops can't be overstated. With corn, there are three micronutrients that I encourage you to focus on. The first is zinc, which is commonly one of the most deficient micronutrients in corn. Zinc is immobile in soil and tissue, so it's critical that plants have a constant supply throughout the season to meet growth and development needs.
In addition to a seed treatment, you can boost early-season zinc levels with a starter fertilizer. You can often apply zinc products with a post emergence herbicide application, and as the season progresses, supplementing foliar zinc at V5 to V8 in corn is sometimes ideal. Next, is manganese levels in corn. Manganese is an essential micronutrient for photosynthesis. The corn plant maximizes photosynthesis from V9 to V15. Manganese is sometimes tied up in the soil, so one of the best ways to get it into the plant is via a foliar application.
Boron is another micronutrient I recommend looking at in corn. One of boron's jobs is to help transfer carbohydrates in the plant. Around tassel time, a plant's stalks and leaves lose boron as it is remobilized to the ear silk and to the tassel; this means that plants may not be able to transfer carbohydrates effectively to the newly developing kernels as efficiently ahead of pollination if boron level are inadequate.
Similar to corn, sufficient amounts of manganese are needed in soybeans to maximize photosynthesis. Timing a manganese application will help ensure that plants have enough of the nutrient to help put on flowers and fill pods. Taking a tissue sample during these times will allow you to assess the needs of hidden micronutrient hunger. Remember that manganese makes the entire photosynthetic process more efficient.
Analyzing boron levels in soybeans is also something to look into. Similar to corn, boron in soybeans plays a role in plant health and takes the carbohydrates produced via photosynthesis and moves them throughout the plant. Pairing boron with manganese in soybeans is a one-two punch for optimal micronutrient management. First, manganese increases photosynthesis efficiency and carbohydrate production, then boron ensures that those carbohydrates are remobilized within the plant.
Soil testing is the best way to identify these differences and to adjust liming and fertilization practices before planting. Predicting deficiencies for secondary nutrients and micronutrients from a soil test is much more difficult than for the major nutrients.
Most micronutrient tests and recommendations were developed for specific soil types and conditions, and it is difficult to adapt these tests to a wide range of soil types and other conditions. Micronutrient test might also have an extra cost above the normal soil test fee. Contact the Pulaski County Extension Office at 606-679-6361 for more information. Information was gathered from a Jon Zuk article "Micronutrients Aren't Optional" and AGR 57.