Know where to look for deficiencies to set the stage for preventive management
Minor element, big potential for trouble. Fortunately, zinc deficiency occurs only in certain soil conditions and environments, but in the right circumstances—for example, calcaric soil with a high pH reading—zinc deficiency can easily rob 15 bu. to 20 bu. of corn per acre, says Farm Journal Field Agronomist Ken Ferrie.
"Zinc and other minor elements aren’t called micronutrients because their role in crop production is minor," Ferrie says. "On the contrary, they are called micronutrients because plants only need small amounts, compared with macronutrients such as nitrogen, phosphate and potash.
"Micronutrient problems can often be fixed with small applications—from 1 lb. to 3 lb. per acre. But if deficiencies are not corrected, they can have a serious impact on yield," he adds.
Beginning with zinc, we’ll take an in-depth look at micronutrients in upcoming Nutrient Navigator articles. "Micronutrients are sort of like vitamins," Ferrie says. "Even if you consume a healthy balanced diet, you can run into trouble if you are missing just one vitamin. It’s the same with crops and micronutrients."
In plants, zinc plays several important roles, all of which help drive yield.
"Zinc is involved in protein synthesis," Ferrie says. "It plays a big role in grain and seed production, especially silk emergence in corn, because it affects the flowering parts of the plant. Zinc helps drive metabolic processes and helps the plant maintain its hormonal balance."
In corn, zinc deficiency causes shortening of the internodes, so plants are shorter. In this Farm Journal Test Plot, conducted by Farm Journal Field Agronomist Ken Ferrie, the corn on the right is taller because the starter fertilizer contained zinc. The shorter corn on the left received starter fertilizer without zinc.
Problem-prone soils. Since zinc deficiency is not common, there’s usually an underlying reason when it occurs, Ferrie says. Understanding those reasons will tell you where and when to anticipate problems.
"Zinc deficiency is common in calcaric soils because they tend to be alkaline," Ferrie explains. "In high-pH conditions, zinc becomes immobilized and unavailable to plants. Expect zinc problems if soil pH gets above 7.2."
Sandy soils are also prone to zinc issues. "Because they are highly leachable, those soils can’t hold the amount of zinc plants need," Ferrie says. "Abused, eroded soils also might not contain sufficient levels of zinc."
Organic matter content is a factor. "You’re more likely to have zinc issues in soils with 1% organic matter than in soils with 3% to 4%," he says. "At the other extreme, organic soils with 40% to 50% organic matter content also are prone to zinc problems."
Problem environments. Certain environmental conditions set the stage for zinc deficiency.
"The most common zinc deficiency situation I run into is when a farmer has cold, wet conditions at planting, the corn emerges and then the temperature drops," Ferrie says. In this situation, a soil test would show adequate levels of zinc. But reduced microbial activity, resulting from the lower temperature, reduces the soil’s ability to release zinc for the plants.