Nutrient Deficiency Symptoms

The preferred way to handle nutrient deficiencies is to identify annual crop needs with soil testing, perennial crop needs with plant analysis, and to correct the deficiencies before the crop is established or deficiency symptoms appear. However, soils are very variable in nutrient levels. Portions of fields low in a certain nutrient may not show up in a normal composite soil sample. The chemistry of some nutrients, such as iron and manganese, is very complex and difficult to predict with a simple soil test. Thus, deficiencies of some nutrients can sometimes appear even with a good soil testing program. Certain nutrient problems are sometimes so rare that regular soil analysis requests do not include testing for those nutrients. Nutrient deficiency symptoms are often the first clues to a nutrient problem within a field.
Plants which are under stress show unusual growth patterns or coloration. These visual symptoms are called deficiency symptoms. Deficiency symptoms can sometimes be confused with other complex field events, such as high water tables, salt damage, disease, drought, herbicide stress and varietal differences. Deficiencies can also be so slight that they are confused with other problems. If more than one deficiency is present, one can be more dominant in its symptoms, obscuring the symptoms of the other element.

Terminology of nutrient deficiencies

Chlorosis

General yellowing of the leaf tissue. A very common deficiency symptom, since many nutrients affect the photosynthesis process directly or indirectly.

Coloration abnormalities

Some deficiencies lower the amount of photosynthesis and chlorophyll which is produced by the plant. Other colored compounds can then become dominant. When normal nutrient sinks are not available, the plants can store up excess sugars within other compounds which have distinct colors of red, purple, or sometimes brown. The absence of chlorophyll altogether causes the plant to turn white.

Firing

Yellowing, followed by rapid death of lower leaves, moving up the plant and giving the same appearance as if someone touched the bottom of the plants

Interveinal Chlorosis

Yellowing in between leaf veins, but with the veins themselves remaining green. In grasses, this is called striping.

Necrosis

Severe deficiencies result in death of the entire plant or parts of the plant first affected by the deficiency. The plant tissue browns and dies. This is called necrosis. The tissue which has already died on a still living plant is called necrotic tissue.

Stunting

Many deficiencies result in decreased growth. This can result in shorter height of the affected plants.

Functions of the 13 soil supplied essential elements

Nitrogen

An essential component of amino acids, and therefore all proteins. An essential component of nucleic acids, and therefore needed for all cell division and reproduction. Enzymes are specialized proteins, and serve to lower energy requirements to perform many tasks inside plants. Nitrogen is contained in all enzymes essential for all plant functions.

Phosphorus

A component of the compound within plants which supply the energy to grow and maintain the plant. Part of cell membranes, the structures which selectively keep out unneeded compounds and allow in those compounds which are needed for the plant cells to function correctly. A part of DNA and its relatives. Needed for cell division and for reproduction.

Potassium

Activates certain enzymes. It regulates stomate opening, which in turn regulates air flow into the leaf and transpiration of water out of the leaf. it acts to balance charge between negatively and positively charged ions within plant cells. It regulates turgor pressure, which helps protect plant cells from disease invasion. In certain plants, potassium can be replaced by sodium.

Sulfur

Sulfur is a part of certain amino acids and all proteins. It acts as an enzyme activator and coenzyme (compound which is not part of all enzyme, but is needed in close coordination with the enzyme for certain specialized functions to operate correctly). It is a part of the flavor compounds in mustard and onion family plants.

Calcium

Calcium is a part of cell walls and regulates cell wall construction. Cell walls give plant cells their structural strength. Enhances uptake of negatively charged ions such as nitrate, sulfate, borate and molybdate. It balances charge from organic an ions produced through metabolism by the plant. Some enzymes are regulated by Ca-calmodulin.

Magnesium

Magnesium is the central element within the chlorophyll molecule. It is an important cofactor the production of ATP, the compound which is the energy transfer tool for the plant.

Boron

Boron is important in sugar transport within the plant. It has a role in cell division, and is required for the production of certain amino acids, although it is not a part of any amino acid.

Molybdenum

Molybdenum is needed for the reduction of absorbed nitrates into ammonia prior to incorporation into an amino acid. It performs this function as a part of the enzyme nitrate reductase. In addition to direct plant functions, molybdenum is also essential for nitrogen fixation by nitrogen-fixing bacteria in legumes. Responses of legumes to Molybdenum application are mainly due to the need by these symbiotic bacteria.

Iron

Iron is a component of the many enzymes and light energy transferring compounds involved in photosynthesis.

Zinc

Zinc is a component of many enzymes. It is essential for plant hormone balance, especially auxinactivity.

Manganese

Manganese is a cofactor in many plant reactions. It is essential for chloroplast production.

Copper

Copper is a component of enzymes involved with photosynthesis.

Chlorine

Plants use chlorine as chloride ion. Chloride is useful as a charge balancing ion and for turgor regulation, keeping plant cells more free of infection by disease organisms. It is essential for photosynthesis.

Mobility of plant nutrients

Plant nutrients which can move from places where they are stored to places where they are needed are called plant mobile. Nitrogen, phosphorus and potassium are always plant mobile nutrients. Deficiencies are noticeable first on older tissue. Plant immobile element deficiencies are noticeable first on younger tissue. Calcium and boron are always plant immobile nutrients. Sulfur, chloride, copper, zinc, manganese, iron and molybdenum are intermediate in plant mobility. Under certain circumstances the intermediate elements are mobile. Mobility in intermediate elements may be linked to the breakdown under low nitrogen conditions of amino acids and proteins in older parts of the plant, and the mobility of these organic compounds to younger parts of the plant in the phloem stream. Under good nitrogen availability, these elements are mostly immobile.

Value of plant nutrient deficiency keys

Use of this plant nutrient deficiency key should be considered first as the first step toward understanding deficiency symptoms in the field secondly as an educational tool to be used in conjunction with soil testing and plant analysis. Environmental stress such as drought, wet conditions, disease, heat and agchemical interactions can easily be misinterpreted as deficiency symptoms. Photographs of nutrient deficiencies are useful in diagnosis, but fieldexperience and a knowledge of field history based on local experience is the best diagnostic aid.