Zinc (Zn) is taken up by plants as the divalent Zn2+ cation. It was one of the first micronutrients recognized as essential for plants and the one most commonly limiting yields. Although Zn is required in small amounts, high yields are impossible without it.
Protein synthesis and growth regulation require Zn. Reduced hormone production due to a Zn-deficient plant will cause the shortening of internodes and stunted leaf growth.
Zinc is much less mobile within the plant, so deficiency symptoms first appear on the younger leaves.
Zinc aids synthesis of plant-growth substances and enzyme systems, and is essential for promoting certain metabolic reactions, which are particularly critical in the early growth stages.
Zinc (Zn) deficiency is growing in the Midwest, and it’s more likely to occur in corn than soybean fields. This is happening in part due to earlier planting of corn in cool and moist soil. Also, more residue resulting from higher grain yields places added stress on seedlings to absorb Zn from soil.
Zinc is heavily involved in enzyme systems that regulate the early growth stages, and is vital for fruit, seed and root system development; photosynthesis; formation of plant growth regulators; and crop stress protection. Further, Zn is a team player with nitrogen (N), phosphorus (P) and potassium (K) in many plant-development processes.
Soils require Zn in very small amounts compared with N or K. Only about a half-pound of Zn is needed per acre for high-yield (180 bushels per acre) corn production. Sixty-bushel wheat needs about 0.28 pound of Zn per acre. Yet, lack of Zn can limit plant growth, just like N or K, if the soil is deficient or crop uptake is restricted.
In addition to being an essential component of various enzyme systems for energy production, Zn is required in protein synthesis and growth regulation. Zinc-deficient plants also exhibit delayed maturity. Since zinc is not mobile in the plant, Zn-deficiency symptoms occur mainly in new growth. This lack of mobility in plants suggests the need for a constant supply of available zinc for optimum growth.
The most visible Zn-deficiency symptoms are short internodes (rosetting) and a decrease in leaf size. Chlorotic bands along the midribs of corn, mottled leaves of dry beans and chlorosis of rice are characteristic Zn-deficiency symptoms. Loss of lower bolls of cotton and narrow, yellow leaves in the new growth of citrus also have been identified as symptoms of Zn deficiency. Delayed maturity also indicates Zn-deficient plants.
Zinc loss takes place in many ways. Deficiencies are mainly found on sandy soils low in organic matter and on organic soils. They occur more often during cold, wet spring weather and are related to reduced root growth and activity. Zinc uptake by plants decreases with increased soil pH. High levels of available P and iron in soils also adversely affect the uptake of Zn.Dig even deeper into Zinc
Symptoms of deficiency can vary across crop species, but similarities exist for how nutrient insufficiency impacts plant tissue color and appearance. Nutrient deficiencies are commonly associated with the physical location on the plant (i.e., whether the symptoms are primarily observed on older versus newly formed plant tissue), but these symptoms can spread as the severity of the deficiency progresses.
All photos are provided courtesy of the International Plant Nutrition Institute (IPNI) and its IPNI Crop Nutrient Deficiency Image Collection. The photos above are a sample of a greater collection, which provides a comprehensive sampling of hundreds of classic cases of crop deficiency from research plots and farm fields located around the world. For access to the full collection, you can visit IPNI's website.