Basic Symptoms Of Nutritional Deficiencies

Introduction

Plant nutrient elements are divided into two groups called Macro- and Micro-elements. The effect of the most limiting nutrient element can be illustrated by trying to fill a drum or barrel with holes at various levels on its side. Each hole represents the relative optimal concentration of a nutrient element. In the sketch below, nitrogen (N) is present at 90% and potassium (K) at 30% of their respective optimal concentrations. To fill the drum, one has to first of all block the hole representing K. Thereafter, you can fill the drum to the level where phosphorus (P) becomes the most limiting nutrient element.

If you first block the nitrogen (N) hole before blocking the K hole you still will not be able to fill the drum more than 30%. Therefore, to fill the drum all nutrient elements must be present at their respective optimal concentration (100% level) but getting the N level to 100% and not the K level will not enable the plant to produce at 100% capacity. Although molybdenum is required in very small quantities compared to nitrogen, the shortage of this element will still cause the plant to produce at only 40% of its capacity in the example below.

Macro Elements

Soil fertility is a collective term used to describe the status of the soil in terms of phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg) and to some extent, nitrogen (N). Fertile soil contains these nutrient elements in adequate quantities to sustain plant growth.

The Symptoms of Nutrient Deficiencies

Identifying Nutrient Deficiencies In Plants

The most important features of nutrient element deficiencies are:

• The leaf should display the same symptom on both the left-hand and right-hand sides of the midrib. This is important in distinguishing between nutrient deficiencies and leaf symptoms caused by other factors.
• Nutrient deficiency symptoms appear first on either new or old leaves. From there the symptom can spread to the entire plant.
• Certain nutrient deficiency symptoms appear first or are more noticeably on fruit.
• Nutrient deficiency starts with mild symptoms and develops into severe symptoms.

Correcting Nutrient Deficiencies

The first response to detecting nutrient deficiency symptoms is to report it to the supervisor or manager.

The presence of nutrient deficiency symptoms is a sign of an unsuccessful fertilisation program. Deficiency symptoms generally appear after the shortage has had an impact on the plant and/or production. The fertilisation program should provide methods to identify and correct short supplies of any essential nutrient element before it impacts the crop.

Rectifying nutrient deficiencies is seldom a simple matter of applying the nutrient. Very often the deficiency is the result of factors other than an absolute short supply. A deficiency can be induced by other factors that convert the specific nutrient into an unavailable form. It could also be the nutrient has been converted to a less active form. To improve the supply of the specific nutrient, one needs to determine why its supply is not optimal (the best it can be) and try to correct that.

Once it has been applied to the plant, there is no guarantee that the active form will last long enough to result in the required physiological reactions. To maintain optimal concentrations of the available nutrient elements in the trees, enough of the nutrient in the available form must be present to be utilised by the plant.

The table below lists the most common causes and factors associated with nutrient deficiencies, and the corrective measure that can be taken.

Symptoms of Nutrient Deficiencies in Crops and Potential Corrective Actions