Agronomy Update November 2018
Posted on November 05, 2018
MANAGEMENT
By: Jessica Stacy, Product Specialist
Farming is variable. Some years are great, and you can throw everything but the kitchen sink at your crop; other years, not as much. When crop prices are less than ideal, nutritional “add-ons” and stimulant-type products are typically the first to get cut. However, when micronutrients are overlooked in crop production, yields can suffer significantly. This month, we are going to take a deeper dive into the micronutrient zinc to better understand its vital role in crop production, conditions that may limit its uptake, and deficiency symptoms.
Zinc holds a lot of power in crop production, as it is necessary for many plant functions, including:
- Auxin production for leaf sizing
- Seed and grain formation
- Plant maturity
- Growth regulation and cell elongation
- Formation of enzyme systems and protein synthesis
- Transportation of calcium throughout the plant
When you consider all these functions, it is obvious zinc plays a heavy role in maximizing crop yields. Research performed by the University of Nebraska supports this claim, suggesting corn yield losses of up to 53 bushels per acre can occur in the absence of zinc (figure 1). 
Figure 1: Table demonstrating findings from a study conducted by University of Nebraska.
Considering how important zinc is in crop production, it is vital to recognize conditions that may limit its availability to the plant. Cool, wet, and cloudy weather during the growing season can limit zinc uptake. In addition, sandy soils, low organic soils, and high pH soils decrease zinc availability. Zinc is immobile and relies on root interception for uptake. Compacted soils will impede root growth, and zinc will be limited because roots cannot grow through the compacted root-zone to reach zinc sources within the soil profile.
In soils with high phosphorus levels, mycorrhizal fungi populations are decreased. As a result, these healthy soil fungi are not extending a crop’s root system to naturally pull in more mineral nutrition, including zinc. A 10:1 ratio of P:Zn in a soil test provides optimal zinc availability.
Beyond understanding the role and challenges of zinc in crop production, it is equally important to be able to identify and diagnose a zinc deficiency. As shown in figure 2, zinc deficiencies in corn are visually exhibited as white to yellow bands beginning at the base of the leaf, not extending to the leaf tip. The midrib, leaf margins, and leaf tip remain green. Soybean visual symptoms include yellow to brown coloration of leaf edges and tips (figure 2). Since zinc is immobile, deficiency symptoms are seen in new leaf growth. Zinc deficiency does not always exhibit in visual symptoms.
A zinc deficiency may often be mistaken as a magnesium or sulfur deficiency in corn (figure 3). As a result, it is always important to take tissue samples to properly diagnose leaf symptom deficiencies. Additionally, a soil sample and maintaining proper zinc soil levels by including a zinc in your starter or broadcast applications, will prevent symptoms from appearing in the leaves.
Figure 2: Corn and soybeans plants exhibiting visual deficiency symptoms of zinc.
Figure 3: Corn leaf with diagnosed magnesium deficiency. Visual symptoms look similar to zinc deficiency.
As discussed, overlooking zinc in crop production could have detrimental effects on final yield. Zinc is necessary for many functions within the plant, but its availability can be challenging. The Andersons offers several zinc options for both starter and foliar applications. Refer to the Zinc Solutions Sheet to see the full product offering and to decide which zinc is right for you and your operation.
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