Micronutrients fertilizer are those essential elements required by plants in small quantities to encourage plant growth and also promote maximum yields thereby increasing your harvest quality to enable you to make more profits.
Micronutrients make a significant impact and play an active role in plant root development, fruit setting, grain fillings, fertilization, seed viability, flower initiations, plant vigor, and health as well as disease-resistant ability.
Examples of the essential micronutrients required by plants include boron (B), chlorine (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), and zinc (Zn).
Generally, with garden-rich soil filled with micronutrients fertilizer, nutrient-rich foods for humans and animals can be guaranteed with little or no stress.
However, critical plant functions are often limited if micronutrients are not available resulting to plant abnormalities, reduced growth, and lower yield.
Therefore to keep your garden soil rich with the micronutrients it needs, I will recommend adding organic compost into the soil.
This is because ordinarily, the living things that go into the compost, for example, the grass clippings, leaves, plants trimmings, table scraps, etc. all already contain the various amounts of micronutrients your soil needs.
Read Also: Harmattan and Its Effect on Crop Production
Now, we are about to discuss each of the essential micronutrients required by plants (Crops); their importance, deficiency symptoms and how to prevent their deficiences… Keep reading for more information!
7 Most Essential Micronutrients Fertilizer in Crop Production
(1) Boron (B)
Boron (B) is one of the required micronutrients fertilizer for crops growth. It is a component of plant cell walls and reproductive structures, it is required in small amounts and is prone to movement within the soils.
Major Functions of Boron in Plants (Crops)
Boron is essential for a variety of plant functions, including cell wall formation and stability, the structural and functional integrity of biological membranes, the movement of sugar or energy into plant growing parts, and pollination and seed set.
In legume crops, adequate Boron is also required for effective nitrogen fixation and nodulation.
Boron deficiency frequently results in empty pollen grains, low pollen vitality, and fewer flowers per plant. As shown in the soybean and canola photos, a lack of Boron can also stunt root growth (see Picture 1).
Boron Deficiency Symptoms
Most crops are unable to transport Boron from vegetative tissues to actively growing, meristematic plant tissues such as shoots, root tips, flowers, seeds, or fruits. Rather, Boron transport takes place primarily in the xylem channel as a result of transpiration. As a result, deficiency symptoms appear first in newly developed plant tissue, such as young leaves and reproductive structures (see Picture 2).
Stunted development and death of meristematic growing points are common in severe Boron deficiency. Other common reactions include decreased root elongation, flower seed failure, and fruit abortion. Low Boron supply may also have an adverse effect on pollination and seed set, even if there are no visible symptoms of leaf deficiency.
Picture 3: Growth of sunflower plants with sufficient and deficient boron supply under low and high light conditions. Plants under low boron supply are quickly damaged when exposed to high light intensity (courtesy of I. Cakmak; see also Cakmak and Römheld, 1997, Plant Soil, 193:71–83).
Tips for Preventing Boron Deficiency
I recommend that you Soil-test your fields every two years to gain a thorough understanding of your field’s nutrient levels. Make sure to compare your yield goals to current nutrient requirements, and consult with an agronomist about your options.
Because there is a fine line between deficiency and toxicity, it is critical to apply the appropriate amount of Boron at the appropriate rate and from the appropriate source.
(2) Chlorine (Cl)
Chlorine (Cl) is an essential micronutrients fertilizer for higher plants and plays a role in a variety of physiological metabolism processes.
The chloride concentration in the plant influences yield and quality formation for two reasons. To begin with, chlorine is a mineral nutrient, and a lack causes metabolic issues that impede growth.
However, chloride deficiency is uncommon in the field due to the low requirement of most crops. Second, excess chloride in chloride-salinity causes severe physiological dysfunctions that impair both quality and yield formation.
Osmotic and stomatal regulation, oxygen evolution in photosynthesis, and disease resistance and tolerance are among its functions in plant growth and development.
If there is an adequate supply of Chlorine, it improves the yields and quality of many crops including onions and cotton, if the soils are deficient in this nutrient.
The chloride ion has the potential to degrade the quality of plant-based products by imparting a salty flavor that reduces the market appeal of products such as fruit juices and beverages.
The majority of the quality issues, however, are caused by physiological dysfunctions caused by chloride toxicity: The shelf life of persimmons is reduced due to autocatalytic ethylene production in fruit tissues.
High chloride concentrations in soil can increase cadmium Phyto-availability, causing it to accumulate in wheat grains above dietary intake thresholds. Also when too much Chlorine is present, it can be a major component of salinity stress and toxic to plants.
However, when crops are grown on moderately salinized chloride soils, nitrate fertilization may be used to suppress chloride uptake through the use of antagonistic anion-anion uptake competition.
Chlorine (Cl) Deficiency Symptoms
Deficiency in Chlorine however reduces plant productivity and the following are deficiency symptoms of chlorine:
Chloride deficiency can reduce photosynthetic area by causing leaf bronzing or dappled chlorotic spots, prominently seen in wheat.
Another symptom of chloride deficiency is wilting due to a restricted and highly branched root system with stubby tips.
Chlorosis, wilting, and restricted root systems all lead to reduced plant productivity and potential yields.
Read Also: Measures of Improving Field Crop Production
(3) Copper (Cu)
Many enzymatic activities in plants, as well as the production of chlorophyll and seeds, require copper.
Copper (Cu) activates enzymes and catalyzes reactions in several plant-growth processes. The presence of Cu, which aids in protein synthesis, is also linked to vitamin A production.
Copper is essential for photosynthesis, plant respiration, and carbohydrate and protein metabolism in plants. Copper also improves the flavor and appearance of vegetables and flowers.
Copper deficiency which affects onions, lettuce, and carrots as well among many other crops can make small grains more susceptible to diseases like ergot, which can result in significant yield loss, also on the other hand, can occur in soils with a high organic matter content and in sandy soils.
Cereal grains such as wheat, barley, and oats are more susceptible to copper deficiency when grown on copper-deficient soils.
Copper (Cu) Deficiency Symptoms
Because copper is immobile, its deficiency symptoms appear in the newer leaves and differ depending on the crop.
It’s deficiency symptoms typically begin with cupping and a slight chlorosis of the entire leaf or between the veins of the new leaves. Small necrotic spots may form within the chlorotic areas of the leaf, particularly on the leaf margins.
As the symptoms worsen, the newest leaves shrink in size, lose their sheen, and in some cases wilt. The apical meristems may become necrotic and die, preventing lateral branch growth. Plants typically have a compact appearance as the distance between the leaves on the stem shortens.
The color of flowers is frequently lighter than usual. Excess potassium, phosphorus, or other micronutrients can cause copper deficiency indirectly. A high pH of the growing medium can also cause a copper deficiency because it is less available for plant uptake.
Normal rose leaf on the right in comparison to copper deficient leaves. Notice the smaller size, curling and chlorosis. Picture credit: University of Florida.
Mum leaf on the left is normal while the one on the right has copper deficiency. Notice the leaf size and chlorosis.
Excess copper on the other hand, has the potential to limit root growth by burning the root tips and causing excessive lateral root growth. Copper levels in soil can compete with plant iron and, in some cases, molybdenum or zinc uptake.
At first, the new growth may appear greener than usual, but it will soon show signs of iron deficiency or other micronutrient deficiencies. If not treated, copper toxicity can reduce branching and eventually lead to plant decline.
Copper, like most micronutrients, is more available when the pH of the growing medium is low, so check the pH of the growing medium if copper toxicity is present and because copper is an active ingredient in some fungicides, it is critical to rinse the foliage before testing the tissue. Plants that are most sensitive to copper toxicity are legumes.
Read Also: Different Systems of Crop Production
(4) Iron (Fe)
Iron in plants is involved in the synthesis of chlorophyll and is required for the maintenance of chloroplast structure and function.
Iron, like iron in the human body, aids in the transport of other essential elements throughout the circulatory systems of plants, and the most important of these is oxygen.
Iron aids in the movement of oxygen throughout the plant’s roots, leaves, and other parts, resulting in the green color that indicates a healthy plant.
Iron is also required by many plants to complete the enzyme functions that keep the plant alive.
Iron (Fe) Deficiency Symptoms
Even though plants only require a trace amount of iron, its absence can have disastrous consequences. Iron deficiency is most commonly manifested as chlorosis.
This is the term used to describe a condition in which new leaves are yellow rather than green, though they still have green veins.
The yellow color is caused by a lack of oxygen transport, which is caused by iron deficiency.
The plant’s leaves do not receive enough oxygen if iron is not present. They can’t produce enough chlorophyll if they don’t have enough oxygen.
The green color is absent in the absence of chlorophyll and if the iron deficiency persists, older leaves will develop chlorosis and turn yellow.
The condition can then progress, resulting in leaf loss and poor overall growth until the plant dies.
(5) Manganese (Mn)
Manganese (Mn) is an essential micronutrient for plant growth and development, as it maintains metabolic roles in different plant cell compartments.
Manganese is an important component of many biological systems in plants, including photosynthesis, respiration, and nitrogen assimilation. Manganese also plays a role in pollen germination, pollen tube growth, root cell elongation, and root pathogen resistance.
Manganese (Mn) is essential in plant oxidation and reduction processes, such as electron transport in photosynthesis. Manganese has also been found to be involved in chlorophyll production, and its presence is required in Photosystem II.
Manganese functions as an activating factor, causing the activation of over 35 different enzymes and due to manganese’s metabolic role in nitrate-reducing enzyme activity and activation of enzymes that play roles in carbohydrate metabolism, the use of manganese-containing fertilizers increases the efficiency of photosynthesis and carbohydrates synthesis such as starch.
Manganese (Mn) Deficiency Symptoms
Manganese deficiency symptoms, which are often confused with iron deficiency, manifest as interveinal chlorosis (yellow leaves with green veins) on young leaves, as well as tan, sunken spots in the chlorotic areas between the veins.
Plant growth can also be slowed or stunted. Manganese deficiency can occur when the pH of the growing medium exceeds 6.5, because manganese becomes bound and unavailable for uptake.
Low fertilizer application rates, the use of general purpose fertilizers (which typically have lower micronutrient contents), excessive leaching, or the application of too many iron chelate drenches can all lead to deficiency.
(6) Molybdenum (Mo)
Molybdenum in plants is a trace element found in soil that is required for nitrate reductase enzyme synthesis and activity.
It is required for two enzymes that convert nitrate into nitrite (a toxic form of nitrogen) and then into ammonia, which is then used to synthesize amino acids within the plant.
It is also required by legumes’ symbiotic nitrogen-fixing bacteria to fix atmospheric nitrogen. Molybdenum is also used by plants to convert inorganic phosphorus into organic forms.
It aids in the nitrogen, oxygen, and sulfur cycles in plant growth. Plants get their molybdenum from the soil. Molybdate is the form of the element that plants can absorb. Molybdenum is less available for plant growth in sandy and acidic soils.
Even as a trace mineral, molybdenum is required for plant growth and without enough of the mineral, leaves turn pale and eventually die, flowers fail to form, and some plant species develop whiptail, a condition characterized by malformed leaf blades.
Legumes are unable to obtain the bacteria required for nitrogen fixation at their root nodes. Necrosis of cell tissues and malfunctioning vascular systems also contribute to the general decline in plant health. Broccoli, cauliflower, soybeans, clover, and citrus are the most commonly affected crops.
Molybdenum is required by plants to aid in nitrogen absorption. It is also required for the absorption of potassium. Molybdenum use in other plants improves plant health and growth.
Molybdenum (Mo) Deficiency Symptoms
Because molybdenum is so closely linked to nitrogen, its deficiency can easily be confused with nitrogen deficiency. Because molybdenum is the only micronutrient that moves within the plant, deficiency symptoms appear on older and middle leaves but spread up the stem and affect new leaves.
In poinsettias, it appears as thin chlorotic leaf margins around the leaf perimeter, followed by necrotic margins. In some crops, the entire leaf turns pale, which is often followed by marginal necrosis.
Leaves can be misshapen, and in the case of cauliflower, this can result in ‘whiptail,’ in which the midrib of the leaf grows but the width of the leaf blade is severely restricted, causing the leaves to be narrow.
Plant growth and flower formation will be restricted in the advanced stages. Crucifers (broccoli, cauliflower, cabbage), legumes (beans, peas, clovers), primula and poinsettias are the crops most sensitive to molybdenum deficiency.
Molybdenum deficiency in cauliflower causes a condition called whiptail in which the leaves have a thin, strappy appearance.
Because molybdenum is required for the conversion of nitrate to ammonia within the plant, feeding mainly nitrate fertilizer will cause a molybdenum deficiency sooner than with ammoniacal fertilizer.
According to research, high sulfates can reduce plant uptake of molybdenum. Molybdenum is the only micronutrient that becomes inaccessible as the pH of the growing medium drops.
Therefore I recommend that you check the pH of the growing medium if a deficiency occurs and consider adding a molybdenum fertilizer supplement if the pH is ideal for the crop.
Classic molybdenum deficiency in poinsettia is shown as a thin, leaf margin chlorosis.
This cucurbit plant is exhibiting molybdenum deficiency on the old leaves as overall yellowing, leaf margin necrosis and some interveinal chlorosis.
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(7) Zinc (Zn)
Zinc is an essential component of many enzymes that are responsible for many metabolic reactions in all crops. Plant growth and development would be halted if certain enzymes were not present in plant tissue.
Zinc is a micronutrient that is recommended in fertilizer programs for corn, sweet corn, and edible beans.
In zinc-deficient plants, carbohydrate, protein, and chlorophyll formation is significantly reduced. As a result, a consistent and continuous supply of zinc is required for optimum growth and yield.
Zinc aids the plant in the production of chlorophyll and when the soil is deficient in zinc, the leaves discolor and plant growth is stunted.
Zinc (Zn) Deficiency Symptoms
It’s difficult to tell the difference between zinc deficiency and other trace element or micronutrient deficiencies by looking at the plant because the symptoms are so similar.
The main difference is that chlorosis caused by a lack of zinc begins on the lower leaves, whereas chlorosis caused by a lack of iron, manganese, or molybdenum begins on the upper leaves.
Zinc deficiency causes chlorosis, a type of leaf discoloration in which the tissue between the veins turns yellow while the veins remain green.
In zinc deficiency, chlorosis usually affects the base of the leaf near the stem. Chlorosis appears first on the lower leaves and then progresses up the plant.
In severe cases, the upper leaves turn chlorotic and die, while the lower leaves turn brown or purple and die. When plants exhibit these severe symptoms, it is best to pull them up and treat the soil before replanting.
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