Farmers know that nutrition is connected to yield. Crops require differing amounts of approximately 17 elemental nutrients to achieve optimal health and meet their fullest yield potential.
Macronutrients are the ones we think of most often. Nitrogen, phosphorus and potassium are significant contributors to yield and are farmer's first go-to when discussing fertility needs. The secondary macros — calcium, sulfur and magnesium — are well-understood and can be found in many common fertilizer blends.
Don’t Forget the Micronutrients
However, other nutrients are vital for plant processes that often get overlooked. Unlike their macronutrient counterparts, micronutrients are only needed in tiny doses. This chart from Purdue University shows how small those amounts can be.
Micronutrient Uptake of Corn, Soybeans and Alfalfa (lbs./acre)
150 bu Corn
60 bu Soybeans
If farmers want their crops to reach their highest yield potential, they need to balance micronutrients because it's easy to miss their deficiencies and their impact can be huge. Here are five examples of how micros impact crops, signs of deficiency and some treatment options.
Copper is widely a known essential nutrient to plant health, but its availability can be impacted by soil pH and organic matter. Alkaline soils have less available copper, as do soils with high organic matter. Coarse, sandy soils are also prone to copper deficiencies.
Copper helps facilitate respiration and photosynthesis in the plant and is essential for plant metabolism. An inadequate amount of copper can lead to poor growth, delays in flowering and even plant sterility.
Because copper is immobile in soils, symptoms appear in early growth. These symptoms can look like cupping and chlorosis on the leaf margins. Tips of the leaves may have a bluish-green tint. As the plant grows, the newer leaves will be smaller and wilt. Older plants will appear stunted, with soft or limp stalks. These issues will impact the plant’s formation and ultimately yield.
The best way to identify a potential copper deficiency is through soil and tissue testing. Add copper sulfate to a fertilizer blend at three to six pounds per acre to increase copper soil levels.
Iron helps deliver oxygen throughout the plant producing the dark green, sometimes almost black color that signifies crop health. Without iron, the plant turns yellow, like nitrogen deficiency, because the plants can’t move and process nitrogen from the roots.
As with many other nutrient deficiencies, much of the iron in the soil is not in a form the plants can use. Even less iron is available for plant absorption if the soil pH is too high or low. This loss of availability matters because iron maintains chloroplasts, which are involved in photosynthesis, and is essential for many enzyme functions and nitrogen fixation. Plants with iron deficiency will have slower growth, reduced plant size, and lower yield.
Manganese is vital in many critical physiological processes, primarily photosynthesis. It also helps plants create lignin, a polymer that helps strengthen the walls of the plant, making it more resistant to drought, heat and disease.
Most soils contain enough manganese to support healthy plant life, but, as with many nutrients, manganese is often unavailable due to the pH of the soil. If the pH is too high, it’s generally not available. Dry or sandy soil conditions further exacerbate the problem, and magnesium and lime can inhibit manganese uptake.
Manganese has relatively low mobility, so symptoms of deficiency show up in the plant's new growth. This symptom often appears as leaves turning pale green between the veins, eventually becoming paler and brown. Manganese deficient plants will appear stunted in corn with pale yellow leaves and white flecks appearing in chlorotic areas.
Manganese availability is influenced by both temperature and moisture in the soil, making it essential to test both soil and plant tissues. If soils are deficient, apply chelated manganese or manganese sulfate at about 0.5 to two pounds per acre. An additional foliar application may be necessary for extreme deficiency situations.
While Zinc is available in the soil, air and water, it’s generally in a form that plants can’t use. Zinc is a critical component of various enzymes responsible for several crop processes, including growing taller plants, developing stronger roots and withstanding cold temperatures. Zinc is also essential in the formation of carbohydrates, proteins and chlorophyll.
Soil texture, soil temperature, pH and phosphorus levels can all impact zinc availability. Phosphorus and zinc have a negative relationship, meaning high phosphorus levels create deficit zinc.
Signs of zinc deficiency appear quickly and can last throughout the growing season. In corn, zinc deficiency causes broad bands of striped tissue on the leaf closest to the stalk, and plants may appear stunted. In beans, zinc deficiency will appear as a yellowing of the lower leaves that turn bronze or brown over time.
Tissue and soil analysis can confirm zinc deficiency. A water-soluble zinc fertilizer will be needed on the soil or as a starter. A product such as Generate® can also deliver zinc directly to the plant, bypassing the soil reactions that cause tie-up.
Don’t Forget Cobalt
Cobalt is often left off the list of elements essential for plant growth; however, it is a critical element necessary for plants to reach maturity. It helps promote stem growth, elongating the coleoptiles and expanding leaf discs and is an integral component for several enzymes and coenzymes that can affect the growth and metabolism of bacteria that support plant growth.
Cobalt also serves as an activator to help with nutrient uptake, improving the delivery of nitrogen (N), phosphorus (P), and potassium (K). Cobalt (Co) helps keep leaves on the plant longer, increases resistance to drought and helps the plant survive longer.
Diagnosing a cobalt deficiency is generally done through soil testing. If confirmed, growers should adjust the soil pH to around 7 so that the affected plants can still take up the cobalt in the soil more easily.
Agnition Understands the Importance of Micros
At Agnition, we know that balanced micronutrients make plants more successful and help you stretch your fertilizer dollars further. Micros are included in our Generate, Commence® and Procure® product lines because we don’t want to see a single nutrient — or nutrient dollar — wasted and keeping your crop at optimum performance is a part of that goal.