Nutrient Management a self-study course from the MSU Extension Service Continuing Education Series a self-study course from 9 Nutrient Management Module No. 9 CCA 1.5 NM Plant Nutrient CEU Functions and Deficiency and Toxicity Symptoms by Ann McCauley, Soil Scientist; Clain Jones, Extension Soil Fertility Specialist; and Jeff Jacobsen, College of Agriculture Dean Introduction This module is the ninth in a series of extension materials designed to provide extension agents, Certified Crop Advisers (CCAs), consultants, and producers with pertinent information on nutrient management issues. To make the learning ‘active,’ and to provide credits to CCAs, a quiz accompanies this module. In addition, realizing that there are many other good information sources including previously developed extension materials, books, web sites, and professionals in the field, we have provided a list of additional resources and contacts for those wanting more in-depth information about plant nutrient functions and deficiency and toxicity symptoms. Objectives After reading this module, the reader should be able to: 1. Identify and diagnose common plant nutrient deficiency and toxicity symptoms 2. Know potential limitations of visual diagnosis 3. Understand how to use a key for identifying deficiency symptoms 4. Distinguish between mobile and immobile nutrient deficiencies 4449-9 May 2009 Background Discussed in Nutrient Management # Module 2, Plant Nutrition and Soil Q&A 1 Fertility, plants require essential nutrients for normal functioning and growth. A How is plant analysis used plant’s sufficiency range is defined as the range of nutrient necessary to meet the as a diagnostic tool? plant’s nutritional needs and maximize Plant analysis consists of testing growth (Figure 1). The width of this range nutrient concentrations in specific will depend upon individual plant species plant parts during specific growth and the particular nutrient. Nutrient stages (Jacobsen and Jasper, 1991). If levels outside of a plant’s sufficiency nutrient concentrations in a sample range will cause overall crop growth are below or above an established and health to decline due to either a sufficiency range, then the plant is deficiency or toxicity. Nutrient deficiency deficient or in excess for that element. occurs when an essential nutrient is not Plant analyses can be performed available in sufficient quantity to meet relatively quickly in the field using the requirements of a growing plant. semi-quantitative test kits or more Toxicity occurs when a nutrient is in extensively in a laboratory (Havlin et excess of plant needs and decreases plant al., 1999). As a diagnostic tool, plant growth or quality. Common nutrient analysis improves the chances of deficiencies in Montana and Wyoming making a correct diagnosis and can be are nitrogen (N) and phosphorus (P), particularly useful in identifying hidden with some deficiencies of potassium hunger or pseudo deficiencies. (K), sulfur (S), boron (B), chloride (Cl), copper (Cu), iron (Fe), manganese (Mn), and most likely occurs as a result of the and zinc (Zn). Micronutrient deficiencies over-application of fertilizer or manure. are fairly uncommon with deficiencies The three basic tools for diagnosing of B, Cl, Fe, and Zn occurring most nutrient deficiencies and toxicities are often (Nutrient Management Module 1) soil testing; 2) plant analysis; and 3) 7, Micronutrients: Cycling, Testing and visual observations in the field. Both soil Fertilizer Recommendations). Nutrient testing (Nutrient Management Module 1, toxicity is less common than deficiency Soil Sampling and Laboratory Selection) and plant analysis (Q&A #1 and #2) are Deficiency range Sufficiency range Toxicity range quantitative tests that are compared to the sufficiency range for a particular crop. Visual observation, on the other hand, is a qualitative test and is based on symptoms h t such as stunted growth or a yellowing of l a e leaves occurring as a result of nutrient H stress. This module focuses on visual d n a nutrient deficiency and toxicity symptoms h t observed in common crops grown in w o r Montana and Wyoming. G t n a l Visual Symptoms as a P Amount of Available Nutrient Diagnostic Tool Figure 1. Relationship between plant growth and Interpreting visual nutrient deficiency health and amount of nutrient available (Brady and and toxicity symptoms in plants can be Weil, 1999). difficult and plant analysis or soil testing 2 Module 9 • Plant Nutrient Functions and Deficiency and Toxicity Symptoms is necessary to confirm nutrient stress. and corrective actions may or may not be Precautions in identifying nutrient stress effective. Therefore, regular soil or plant symptoms include the following: testing is recommended for the prevention 1. Many symptoms appear similar. For and early diagnosis of nutrient stress. instance, nitrogen (N) and sulfur (S) If visual symptoms are observed, deficiency symptoms can be very alike, record which crop(s) are affected, their depending upon placement, growth location with respect to topography, stage, and severity of deficiencies. aspect, and soil conditions, a detailed 2. Multiple deficiencies and/or toxicities description of symptoms, and time of season that the symptoms first appeared. can occur at the same time. More than Affected field locations can be marked and one deficiency or toxicity can produce monitored over time using either flagging symptoms, or possibly a deficiency or GPS readings. This information will be of one nutrient can induce the useful in preventing nutrient stress for excessiveness of another (i.e., excessive subsequent years. P causing Zn deficiency). 3. Crop species, and even some cultivars of the same species, differ in their ability to adapt to nutrient deficiencies # and toxicities. For example, corn Q&A 2 is typically more sensitive to a Zn deficiency than barley NM( 7). I suspect a nutrient deficiency. How do I 4. Pseudo (false) deficiency symptoms collect a plant sample for submission to (visual symptoms appearing similar to nutrient deficiency symptoms). an analytical laboratory? Potential factors causing pseudo If you suspect nutrient stress, sample when symptoms deficiency include, but are not limited first appear. To ensure quality results, samples should be to, disease, drought, excess water, taken from comparable locations (similar topography, genetic abnormalities, herbicide and aspect, and soil type) and at the same time of day. When pesticide residues, insects, and soil testing samples for plant analysis, it is important to collect compaction. the part of the plant that will give the best indication of the nutrient status of the whole plant. The latest mature 5. Hidden hunger. Plants may be nutrient leaf is typically used, however, appropriate plant parts deficient without showing visual clues. to test will vary with crop type and growth stage (see 6. Field symptoms appear different than Appendix for additional resources). Collect numerous ‘ideal’ symptoms. Many of the plants (20-30) subsamples of parts from plants that appear shown in this module as photographs both abnormal and healthy, if possible. Subsamples may were grown under controlled nutrient be combined for one sample. To gather plant samples, conditions, and deficiency/toxicity use a clean plastic or paper container (metal containers symptoms observed in the field may can contaminate samples). If the samples have soil, or may not appear as they do here. fertilizer, or spray residues on them, clean gently with Experience and knowledge of field a dry brush or with deionized or distilled water. Do not history are excellent aids in determining prolong washing because it can leach nutrients out of the causes for nutrient stress. tissue. Air-dry samples in the shade in either a paper bag or envelope. To avoid decomposition, do not use plastic In addition to the above precautions, bags or send fresh samples. When mailing samples to the visual observation is also limited by time. laboratory, include type and variety of crop, current and Between the time a plant is nutrient past crop management practices, irrigation frequency deficient (hidden hunger) and visual (if applicable), soil type (if known), visual appearance of symptoms appear, crop health and crops, and any insect or disease problems. productivity may be substantially reduced Module 9 • Plant Nutrient Functions and Deficiency and Toxicity Symptoms 3 Diagnosing Nutrient Deficiencies Plant Nutrient Deficiency Terminology COMMON DEFI C IEN C Y SYMPTOM S A first step in diagnosing nutrient Burning: severe localized yellowing; deficiencies is to describe what the scorched appearance. symptoms look like. Each deficiency Chlorosis: general yellowing of the symptom must be related to some function plant tissue; lack of chlorophyll. of the nutrient in the plant (Havlin et Generalized: symptoms not limited al., 1999). The role of each essential to one area of a plant, but rather nutrient in the plant is listed in Table 1 spread over the entire plant. of NM 2. Symptoms caused by nutrient deficiencies are generally grouped into five Immobile: not able to be moved from categories: 1) stunted growth; 2) chlorosis; one part of the plant to another. 3) interveinal chlorosis; 4) purplish-red Interveinal Chlorosis: yellowing in coloring; and 5) necrosis. Stunting is a between leaf veins, yet veins remain common symptom for many deficient green. nutrients due to their varied roles in Localized: symptoms limited to one the plant. For example, when nutrients leaf or one section of the leaf or involved in plant functions such as stem plant. elongation, photosynthesis, and protein production are deficient, plant growth Mobile: able to be moved from one is typically slow and plants are small in plant part to another. stature. Chlorosis and interveinal chlorosis Mottling: spotted, irregular, are found in plants deficient of nutrients inconsistent pattern. necessary for photosynthesis and/or Necrosis: death of plant tissue; tissue chlorophyll (green leaf pigment involved browns and dies. in photosynthesis) production. Chlorosis can result in either the entire plant or leaf Stunting: decreased growth; shorter turning light green to yellow, or appear height of the affected plants.