Diagnosing Nutrient Deficiency and Toxicity Symptoms
by Wesley Chun, ABR, LLC The following list describes general symptoms associated with nutrient disorders in plants. It should be remembered that nutrient deficiencies or toxicities can resemble non-nutritional disorders such as disease or herbicide damage. Use of soil and/or tissue analysis may help confirm whether symptoms are nutritional. Nitrogen (N): • Deficiency- Leaves turn pale green to yellow. Oldest leaves are affected first, but in severe cases the whole plant may be yellow. Growth is usually stunted. Occurs most frequently on sandy soils. • Excess- Nitrogen excess can occur with high rates of nitrogen fertilizer. The result is usually excessive vegetative growth and poor fruit growth. In extreme cases, root burn leading to marginal firing can occur. Phosphorus (P): • Deficiency- Leaves appear reddish-purple. Oldest leaves are affected first. Plant growth is stunted. Common in acid and alkaline soils or those soils low in native phosphorus. Frequently occurs on cool wet soils in the spring; however, plants may grow out of phosphorus deficiency as soil warms. • Excess- High rates of phosphorus fertilizer may induce zinc or iron deficiency. Potassium (K): • Deficiency- Leaves develop gray or tan areas near the margins. Oldest leaves are affected first with characteristic symptoms of scorching around the leaf margins. Occurs on sandy soils and soils low in native potassium. • Excess- High rates of potassium fertilizer can cause salt burn. Soils with high potassium levels can induce magnesium deficiency on sandy soils. Calcium (Ca): • Deficiency-Growing points of plant may die. Younger leaves are affected. Root tips die and root growth is slow. Tipburn of cabbage, cauliflower, lettuce; black heart of celery; and blossom end rot of tomatoes are due to localized calcium deficiency within the plant. These disorders may occur on high calcium soils. Calcium deficiency may occur on acid and/or dry soils. • Excess- Not known to occur. Magnesium (Mg): • Deficiency-Oldest leaves turn yellow between the veins. In severe cases, younger leaves may be affected and older leaves may drop off. May occur on acid soils, sandy soils, or soils with high potassium levels. • Excess- Not known to occur in Minnesota. Sulfur (S): • Deficiency- Symptoms of sulfur deficiency are similar to nitrogen deficiency except that youngest leaves are usually affected first. Can occur on sandy soils low in organic matter. Excess- Rare usually associated with saline conditions. Boron (B): • Deficiency- Usually occurs on younger plant tissue. Growing points die and leaves appear distorted. May cause hollow stem and internal browning in cauliflower and broccoli; cracked stem in celery; internal browning in beets and turnips. Can occur on sandy soils in crops with a high boron requirement. • Excess- Boron can be highly toxic to some plants at low levels. Avoid excess boron applications. Toxicity symptoms usually occur on oldest leaves as a scorching of the margins. Chlorine (Cl): • Deficiency- Rare. Not known to occur in the field. • Excess- Marginal scorch of older leaves. Can occur on salt-affected soils, near streets where deicing salt is used, or when excessive rates of fertilizer containing chlorine are used. Copper (Cu): • Deficiency- Yellowing or dieback of youngest leaves. Sometimes yellowing between the veins can occur. Most copper deficiencies occur on organic soils (peats or mucks). • Excess- Can occur due to continuous use of copper-containing fungicides. May induce iron chlorosis and cause stunted root systems. Iron (Fe): • Deficiency- Yellowing between the veins on youngest leaves; veins remain green (often referred to as interveinal chlorosis). Occurs frequently on high pH soils (pH greater than 7.2). Some plant species more susceptible than others. With acid-loving plants (e.g., blueberry), chlorosis may occur at a pH as low as 5.5-6.0. • Excess- Rare. High levels of iron may induce manganese deficiency. Manganese (Mn): • Deficiency- Similar to iron deficiency. Yellowing between the veins of youngest leaves. Usually only the main veins remain green causing a fishbone-like appearance. In some plants older leaves may develop gray streaks or dots. Occurs on high pH soils (pH greater than 7.2). Can also occur on organic soils with pH greater than 6.0. • Excess- Manganese toxicity can occur on acid soils (pH less than 4.5) or after heat sterilization of greenhouse soils. • Excess symptoms include brown spots on leaves and chlorosis (yellowing). Molybdenum (Mo): • Deficiency- Pale distorted narrow leaves. Causes "whiptail" of cauliflower. Can occur on acid soils (pH less than 5.0). • Excess- Rare. Zinc (Zn): • Deficiency- Short internodes may cause rosetting appearance in trees. Younger leaves usually affected first and may show signs of yellowing between the veins. High levels of phosphorus fertilizer may induce zinc deficiency. Can occur on high pH soils or acid sandy soils. • Excess- May induce iron deficiency.