Small But Mighty: Could Micronutrients Be Limiting Your Yield?

Despite being needed in significantly smaller quantities, micronutrients play just as important a role in crop health as macronutrients like nitrogen, phosphorus and potassium. With insufficient amounts of even one micronutrient, growers could see significant impacts to crop health and yield. To reach their full potential, plants need access to all nutrients throughout their growth cycle, and a strong soil microbiome can help growers provide free nutrition to their crops all season long. 

The list of essential plant micronutrients is long and includes copper, manganese, boron, nickel, iron, molybdenum, zinc and chlorine. Each of these nutrients serves drastically different purposes and a look at just two — boron and zinc — shows the important and unique roles micronutrients play in plant health.

1. Boron: While the optimal amount of boron in the soil varies, boron levels greater than 2 parts per million (ppm) are considered excessively high. For boron deficient soils, application rate recommendations are very low; between 0.5 and 2 pounds per acre. Compare this to nitrogen applications, which are often in excess of 100 pounds per acre, depending on a grower’s nutrient use efficiency score and yield potential.
   
   Even at these low levels, however, boron plays a very important role in crop health by supporting pollen tube growth and germination, cell wall structure and carbohydrate metabolism. Corn plants deficient in boron may be weak or limp, producing poorly developed ears and reduced yield. With sufficient boron, the crop’s cell walls can reach their full potential, improving standability and boosting yield.
   
2. Zinc: Zinc plays a critical role in plant metabolic function, supporting the production of growth hormones, proteins, chlorophyll and carbohydrates. Deficiencies can be spotted in younger leaves first and in corn, will likely appear as bands of pale tissue on either side of the mid rib. Because zinc supports internode length, without sufficient amounts of this nutrient, plants often appear stunted.
   
   Sufficient levels of soil zinc using a DPTA zinc soil test are generally between 0.5 – 0.7 pm, but as with all nutrients, other factors like soil texture can impact crop uptake. Phosphorus and zinc have a particularly complex relationship; research has shown that excessive levels of either nutrient can induce deficiency in the other when soil levels are low. Because of how common large phosphorus applications are, however, phosphorus-induced zinc deficiency is much more common. For growers applying substantial amounts of manure or phosphorus fertilizer, it’s important to keep an eye on zinc levels as well to avoid impacting yield.

No amount of one nutrient can make up for a lack of another; when a crop lacks any nutrient, micro or macro, plant health and yield will suffer. This is Liebig’s Law of the Minimum: growth and productivity of a plant is limited by the scarcest resource. With a deep understanding of their operation and its nutritional limitations, growers can dial in their nutrition program to avoid over-applying nutrients like nitrogen and phosphorus that the crops simply can’t or won’t use, costing growers money. Instead, growers can focus on addressing their fields’ limiting factors and providing the nutrients they need, when and where the plants can use it. 

Soil health plays a key role in ensuring a grower’s crops have access to plant-available forms of micronutrients throughout the season. The organic matter present in healthy soils is an excellent source of many of the micro- and macro-nutrients crops need, in addition to providing other benefits including:

• Increased water-holding capacity
• Improved drainage
• Good soil tilth
• Active soil microbiome

Soil microbes and plants have developed strong, mutually-beneficial relationships. Perhaps the most well known relationships are those between plants and nitrogen-fixing and phosphorus-solubilizing microbes, but a variety of other microbes improve plants’ access to various micronutrients as well.

Products like SOURCE, Sound’s microbiome activator, can also help growers support soil health. SOURCE is a foliar applied chemistry that stimulates and attracts microbes to the root zone. An active soil microbiome supports a bigger root ball, allowing the plant better access to nutrients throughout the season. Tissue tests across the country have consistently shown that plants treated with SOURCE contain more micronutrients. SOURCE works with the microbes already in a growers soil to support soil health and provide in-season access to all nutrients.