A Check-Up Using Nutrient Deficiency Symptoms

Manganese-deficient soybeans

When the uptake of any of the essential nutrients is inadequate, the plant metabolism becomes disrupted and distinctive symptoms often begin to appear. Since nutrients are involved in specific growth processes, deficiency symptoms provide clues to what nutrient might be lacking. However, most nutrient deficiencies begin to interfere with plant productivity long before the symptoms become visible.

Plant tissue testing is needed to verify that a visual symptom is caused by a specific nutrient deficiency. This differs from soil analysis, which verifies a sufficient reserve of nutrients in the soil, but does not account for conditions that may be interfering with nutrient uptake by roots (such as cold, dry, or compacted soils).

Iron-deficient sorghum

When the cause of deficiency symptoms is known, it still must be determined if a prompt nutrient application will correct the problem. There may be economic constraints or difficulties getting equipment into the field to alleviate the deficiency. Foliar sprays of soluble nutrients are often useful to treat deficiencies as they appear during the growing season. Some nutrients may be added to irrigation water and applied via fertigation to correct plant shortages. However, nutrient deficiencies result in permanent loss of growth and plants may fail to recover from severe deficiencies even after corrective measures.

Foliar sprays can be used to correct deficiency

In general, leaf nutrient deficiency symptoms fall into general categories:

• Chlorosis (yellowing) may appear between the leaf veins or impact the entire leaf

• Necrosis (leaf death) usually begins at the leaf tip or edges, or appears between the leaf veins

• Lack of new plant growth as a result of the growing points dying and failure of new leaves to develop

• Accumulation of plant pigments (especially purple-colored anthocyanin)

• Overall plant stunting with normal or abnormal coloring

Boron-deficient citrus fruit

 A shortage of a nutrient does not immediately result in visible deficiency symptoms. Overall plant growth and metabolism is usually hindered for some time before visual symptoms are present. This so-called “hidden hunger” occurs with low levels of chronic nutrient deficiency, and is far more common than visible deficiency symptoms. By the time obvious visual symptoms first appear, the plant can no longer function properly.

Nutrient deficiency symptoms are most useful for diagnostic purposes (and correction) when they are identified as early as possible. Even when supplemental nutrients are applied to correct deficiencies, irreversible damage to yield or crop quality has likely already occurred.

Phosphorus-deficient guava

Environmental stresses also cause abnormal symptoms to appear on plant leaves that may not be directly related to nutrient deficiency. Additionally, plant disease, insect damage, herbicide impacts, or excessive salinity are examples of non-nutrient factors that cause leaf disorders and stunting.

Nutrient deficiency can cause secondary plant damage that is not readily visible. For example, potassium shortages have been shown to reduce plant resistance to various diseases and insects. Many turfgrass diseases are more common under nitrogen-deficient conditions. Maintaining an adequate supply of phosphorus reduces the severity of diseases such as root rot in wheat and barley, and minimizes various infections of corn and soybean.

E-book published by IPNI

 IPNI is developing guides to help growers identify nutrient deficiencies symptoms of important horticultural and agronomic crops. The first e-book was written by Drs. Pitchay and Mikkelsen (on broccoli) and is available for free for download from iTunes® or for small fee from Amazon®. A collection of outstanding images of deficiency symptoms of important world crops is available for purchase at the IPNI store. 

Need a Micronutrient Review?

We’ve all been taught that plants require essential nutrients, but are you keeping up as our understanding of plant nutrition continues to increase? There has been considerable discussion the past few years about the importance of managing nitrogen, phosphorus, and potassium according to the 4R principles of nutrient stewardship of “Right Source, Right Rate, Right Time, and Right Place”, however other nutrients need your attention too.

The essential role of micronutrients is too often overlooked since the quantity required by plants is quite small. For example, did you know that nickel was added to the list of essential micronutrients? While nickel deficiencies are rather rare, a trace amount is essential for specific enzyme reactions in plants. Did you know that cobalt is essential for nitrogen fixation within the nodules of legume roots? How about knowing that silicon is now recognized as a “beneficial” nutrient for many plants?

The Nutrifact series
has great summaries
of each essential nutrient

The International Plant Nutrition Institute recently completed a series of short fact sheets that describe the role of each of the essential plant nutrients. These brief publications will help you learn the latest information on the role each essential plant nutrient and can be viewed at: www.ipni.net/nutrifacts.

“All agronomy is local” is a phrase that summarizes the approach for getting the proper nutrient conditions for each field. Accomplishing the mandate to “keep it local” challenges the skill and knowledge of each farmer and crop adviser, especially as it relates to micronutrient fertilizer decisions. Farmers must continually review yield performance along with the results of soil and tissue analysis as everchanging guides to nutrient planning.

The appearance of plant micronutrient deficiency symptoms raises immediate concerns that something critical was overlooked in the planning stage and that crop yields will likely be reduced. Deficiency symptoms appear in the plant after the internal metabolism has been sufficiently disrupted to show visible problems. Even if no micronutrient deficiency symptoms are observed in the field, many farmers are now conducting their own simple trials to see if a certain micronutrient might be holding back their push for ever-increasing yields.

When a specific micronutrient is lacking, remember that not all fertilizer sources are equivalent in meeting crop needs. Selecting a form of micronutrient that will provide a soluble form of the nutrient requires careful attention. Very little micronutrient is actually needed by plants, but supplying it in an available form is a challenge.

Iron-deficient potato

Adding a small dose of the correct form of micronutrient at planting can be very effective at meeting crop requirements. Getting micronutrients delivered to plant roots can be a challenge if the fertilizer is not uniformly applied across the field. Foliar sprays containing micronutrients can also be useful, but often require repeated application.

Biofortification (increasing the nutrient content in crops) is an often-overlooked benefit from proper fertilization. The content of trace elements in crops reflect the soil properties the plants are grown on. Crop fertilization with appropriate micronutrients offers a simple and cost effective method of improving the nutritional value of food, especially in regions where pernicious malnutrition has had devastating impacts.

It is too easy to overlook the vital role that micronutrients play in successful crop production. Take another look at the principles of 4R Nutrient Stewardship and see if micronutrients are being overlooked as part of your plan.