Mineral Deficiency

Mineral Deficiency In Plants

Scientists have identified 17 elements that all plants need to grow and develop. These are called plant essential nutrients.

Nine of these essential elements are macronutrients. Six of these macronutrients–carbon, oxygen, phosphorus, hydrogen, nitrogen, and sulfur–are needed in large amounts as they make up the organic compounds that form the plant’s structure. The other three macronutrients are potassium, magnesium, and calcium.

The remaining eight essential elements–iron, copper, zinc, manganese, boron, chlorine, molybdenum, nickel–are called micronutrients. Plants need them in tiny or trace amounts.

These essential nutrients are identified and classified in Figure 1 below.

Figure 1. The 17 essential plant nutrients are classified into primary and secondary macronutrients and micronutrients.

Mineral Deficiency in Plants Definition

Mineral deficiency occurs when a plant does not have an adequate supply of an essential nutrient necessary for its growth and development. Plants that lack essential nutrients will not grow effectively and will exhibit a variety of symptoms to indicate deficiency.

Symptoms of Mineral Deficiency in Plants

The symptoms of a mineral deficiency are partially determined by the mineral's role as a nutrient. For example, magnesium deficiency leads to chlorosis because magnesium is a component of chlorophyll.

Sometimes the link between the mineral deficiency and its symptom is not as straightforward.

In addition to the mineral’s role as a nutrient, mineral deficiency symptoms are also determined by the nutrient’s mobility within the plant.

Deficiency in a nutrient that can move freely in the plant would cause symptoms to appear first in older organs because young parts will be using more of the nutrients. Magnesium is an example of a mobile nutrient. As such, we can expect initial signs of chlorosis caused by magnesium deficiency to show in its older leaves.

On the other hand, deficiency in a relatively immobile nutrient tends to affect young organs first. This is because older tissues may have stored some of these nutrients prior to the shortage in supply. Iron is an example of a relatively immobile nutrient. As such, we can expect initial signs of chlorosis due to iron deficiency to appear first in young leaves.

A plant’s mineral requirements may also depend on the season and the age of the plant. Young seedlings, for example, seldom exhibit symptoms of mineral deficiency because their mineral requirements are satisfied by minerals in the seed’s stored reserves.

Micronutrient deficiency is not as common as macronutrient deficiency, and it typically occurs in specific geographic regions because of the soil composition. To test for micronutrient deficiency, the mineral content of the plant or soil can be assessed. The amount needed to remedy a micronutrient deficiency is usually small.

While plants need these nutrients, they must be supplied in appropriate amounts; excessive or deficient nutrients can be detrimental to the growth and development of a plant.

Plant Nutrient Deficiency Symptoms Chart

The symptoms exhibited by a deficiency in each essential nutrient are identified in figures 2 and 3 below.

Figure 2. Common symptoms of macronutrient deficiency in plants.

Figure 3. Common symptoms of micronutrient deficiency in plants.

In order to spot symptoms of mineral deficiency, it is vital to know what a plant species looks like when it is healthy. For example, some plants actually have variegated patterns in the leaves when they are healthy. This can be confused for interveinal chlorosis, the yellowing of tissues that surround veins (Fig. 4).

You might also notice how many of the symptoms of nutrient deficiencies appear similar. Some symptoms might also manifest differently depending on the plant type. It is thus important to have the soil tested by an agricultural soil testing facility to see whether nutrients need to be added to the soil.

Plants might also display symptoms of deficiency for one nutrient but may actually lack another. This is because plants use many micronutrients to process other nutrients or use them simultaneously.

Three Examples of Nutrient Deficiencies in Plants

Let’s discuss how nutrient deficiencies affect plants, what causes them, and how they can be corrected.

Iron Deficiency in Plants

Iron is a micronutrient that all plants need as it plays an important role in chlorophyll synthesis. It is also a component of many vital enzymes needed for a wide range of biological functions.

Iron can be found in most soils occurring in nature, where it can be found in two main forms: ferrous (Fe2+) and ferric (Fe3+). The uptake of iron in plants can be affected by several factors.

Soil pH can affect iron availability. Plants tend to get enough iron from soils with a pH below 6. However, some plants can become iron deficient at a pH of 6, while others can become deficient as soon as pH exceeds 7.

Clayey soils can also affect the uptake of iron because they tend to contain less organic matter which makes iron more available. One way to correct this issue is to add compost.

Soils that do not drain well can cause the roots of a plant to suffocate, affecting their capacity to take up iron. This can be corrected by improving drainage.

Plants deficient in iron will have symptoms including interveinal chlorosis. As it is a relatively immobile element so it affects young leaves first. As the iron deficiency progresses, the veins become lighter and spots begin to appear.

Iron deficiency can be corrected in various ways. It is recommended to have the soil tested first to decide on the best method for correcting the deficiency.

• If the soil has enough iron that the plants can access but the pH is high, the soil pH needs to be lowered. Incorporating elemental sulfur or sulfur compounds into the soil can help lower the soil pH.

• If the pH is at a good level for the plant but the iron content is low, iron needs to be added to the soil. This can be remedied by adding iron fertilizer.

Zinc Deficiency in Plants

Zinc is a component of many vital enzymes that play essential roles in metabolic reactions in plants. Deficiency in zinc can lead to a significant reduction in the formation of carbohydrates, proteins, and chlorophyll.

Zinc can be found in rocks. How much zinc is in the soil depends on how much zinc was present in the rocks and other materials that make up the soil. Sandy soils, leached acidic soils, and mineral soils with low organic matter content tend to have low zinc availability. Plants take up zinc in two forms: divalent ionic zinc (Zn2+) and chelated-zinc.

Zinc deficient plants do not develop normally and will exhibit specific symptoms. For example, zinc deficiency in corn causes wide bands of striated tissue to appear on both sides of the midrib of the leaf. It also causes stunted growth.

Soil tests and plant analyses can determine whether or not a fertilizer needs to be applied. However, in some cases such as in fruit trees, zinc deficiency can be remedied by hammering a few nails into the trunk.

Nitrogen Deficiency in Plants

Nitrogen is one of the essential macronutrients and it is the one that contributes the most to the development and productivity of plants. Nitrogen is a component of proteins, nucleic acids, chlorophyll, and other vital organic molecules needed by plants.

Nitrogen deficient plants exhibit stunted growth. They also undergo chlorosis. As the nitrogen deficiency progresses, leaves begin to dry out and wither.

Nitrogen availability decreases at a pH below 4. It is also typical for sandy and well-drained soils that are prone to leaching to be deficient in nitrogen. Poor aeration can cause nitrates (which is the form of nitrogen that plants need) to split into N₂O.

Nitrogen deficiency can be corrected using various organic and chemical methods. Some of these remedies include:

• Adding compost or animal manure.

• Crop rotation, cover crops, or intercropping using nitrogen-fixing plants.

• Incorporating blood meal, groundnut husks, or coco peat into the soil.

• Adding fertilizers that contain nitrogen.