Plant development slows down if the availability of a critical component gets constrained. The statement “the element is considered to be inadequate when present below the critical concentration” refers to the concentration of the necessary element below which plant development is hindered.
Plants exhibit certain morphological changes when a specific element is absent. These morphological alterations are known as deficiency signs because they are suggestive of specific element shortages. The signs of an elemental shortage differ from element to element, and they go away when the plant receives the lacking mineral nutrition. But if the plant is continually starved, it can finally perish.
The mobility of the element inside the plant affects which areas of the plant exhibit deficiencies signs. The symptoms of a deficit often manifest first in the older tissues for components that are actively mobilised within the plants and exported to young growing tissues. For instance, senescent leaves show signs of nitrogen, potassium, and magnesium deficit initially. These elements become accessible for mobilisation in younger leaves as a result of the breakdown of biomolecules containing them in older leaves.
When the elements are relatively immobile and cannot be transported out of the mature organs, such as when elements like sulphur and calcium are a part of the structural component of the cell and are therefore not easily released, the deficiency symptoms frequently manifest first in the young tissues. The relevance of this component of plant mineral nutrition to agriculture and horticulture cannot be overstated.
Chlorosis, necrosis, stunted plant development, early leaf and bud drop, and cell division suppression are a few examples of the deficiencies that manifest in plants. Chlorosis is the loss of chlorophyll, which causes the leaves to become yellow. The absence of the elements N, K, Mg, S, Fe, Mn, Zn, and Mo is the source of this ailment. Similar to this, a lack of Ca, Mg, Cu, or K results in necrosis, or the death of tissue, especially leaf tissue. Cell division is slowed down when N, K, S, or Mo are absent or insufficient. When plants have low concentrations of certain elements as N, S, and Mo, blooming is delayed.
Nutrient deficiency and management
Generalized symptoms of plant nutrient deficiency
|
Nutrients |
Visual deficiency symptoms | |
|
N |
: | Older leaves, in particular, have a light green to yellow look. There are also growth stunts and poor fruit development. |
|
P |
: | Purple coloration of the leaves, slowed plant growth, and delayed plant development are possible. |
|
K |
: | marginal leaf scorching, erratic fruit development |
|
Ca |
: | poor fruit development and appearance, reduced growth or death of developing tips |
|
Mg |
: | Poor fruit growth and production, initial yellowing of elder leaves between leaf veins progressing to younger leaves |
|
S |
: | Yellowing of young leaves that begins at the base and spreads to the entire plant, similar to signs of N deficiency but occurring on new growth |
|
Fe |
: | Young leaves’ veins initially have prominent yellow or white patches before spots of dead leaf tissue appear. |
|
Mn |
: | Young leaves with interveinal yellowing or mottling |
|
Zn |
: | Young leaves’ interveinal fading, smaller leaves, short internodes, and brown leaf spots on paddy |
|
Cu |
: | Growth is slowed down, terminal leaf buds die, leaf tips become white, and the leaves are twisted and constricted. |
|
B |
: | Terminal buds perish, root crop internal tissues disintegration, apple internal cork dysfunction, flower and fruit development impediment |
|
Mo |
: | Similar to Qualiflower whiptail illnesses, which cause the leaves to burn and wither, and N deficient symptoms |
|
Cl |
: | leaves with chlorosis and partial leaf necrosis |
Nitrogen deficiency in maize
Phosphorus deficiency in maize
Potassium deficiency in maize
Sulphur deficiency in maize
Zinc deficiency in maize
Particularly when nutrient deficit is moderate, conspicuous signs like chlorosis on the plant may not be present. However, with such inadequacies, agricultural yields may be significantly reduced. Plant tissue examination or a loss in production are the only ways to identify this condition, known as hidden hunger.
Management
You can address nutrient deficiencies by
(i) nutrient supplementation by foliar and soil fertiliser applications
(ii) adding organic manure in accordance with fertiliser advice.
|
Deficiency of Nutrient |
Corrective measures |
|
N |
(1) Use of nitrogen fertilizer in the soil.
(2) Foliar spray of urea. |
|
P |
Application of phosphatic fertilizer in the soil e.g., DAP, super phosphate |
|
K |
Use of potassic fertilizer in the soil e.g., muriate of potash. |
|
Ca |
Use of calcium carbonate or calcium hydroxide in the soil. |
|
Mg |
Soil or foliar application of magnesium sulphate. |
|
S |
Soil or foliar application of sulphur or sulphate. |
|
Fe |
Soil or foliar spray of ferrous sulphate. |
|
Mn |
Soil or foliar spray of manganese sulphate. |
|
Zn |
Soil or foliar application of zinc sulphate |
|
B |
Soil or foliar spray of boric acid or borax |
|
Cu |
Soil or foliar spray of copper sulphate |
|
Mo |
Soil or foliar application of sodium molybdate or ammonium molybdate. |
Nutrient Toxicity and Management
Micronutrients are always needed in small amounts, but a modest reduction in them can result in deficiency symptoms, while a considerable excess can result in toxicity. In other words, the components are most effective within a certain range of concentration. Any mineral ion concentration in tissues that causes a 10% reduction in the dry weight of those tissues is regarded as hazardous. Varied micronutrients have quite different critical concentrations. Identification of the poisoning signs is challenging. Varied plants have different degrees of toxicity for any given element. An overabundance of one element can frequently prevent the absorption of another element.
Manganese (Mn) and boron (B) are more frequently toxic nutrients in crops than other nutrients.
Boron toxicity
Manganese toxicity
On acidic soils, manganese toxicity is present. It is crucial to understand that manganese competes with magnesium and iron for absorption and with magnesium for enzyme binding. In the shoot apex, manganese also prevents calcium transfer. Therefore, an overabundance of manganese may result in iron, magnesium, and calcium deficiency. Therefore, symptoms of iron, magnesium, and calcium insufficiency may mimic those of manganese intoxication.
In irrigated areas with particularly high B-content well or irrigation waters, borax toxicities can develop. The majority of other nutrient toxicities take place when significant amounts of the problematic nutrients have been added to waste, including sewage sludge. Nutrient toxicities are a risk for crops planted close to mines and smelters. Typically, burning, chlorosis, and leaf yellowing are the signs of poisoning in plants. Crop quality may suffer as well as lower yield due to toxins.
Prevention of toxicity
(1) Liming can lessen the toxicities of other nutrients, with the exception of Mo.
(2) Reducing metal loading and nutrient toxicity in crops should be accomplished by applying fertilisers at prescribed rates and using waste products, such as sewage sludge and coal fly ash, in a safe and regulated manner.
(3) When toxicity is detected, it is advised to choose crop species and genotypes that are less toxic.
(4) Enough drainage was provided since, in wet conditions, the availability of nutrients like Fe and Mn rises to dangerous levels.
(5) If the level of B and Cl in the ground water is too high, it must be stopped or diluted before applying water.
(6) Some of the hazardous elements are bound when enough organic matter is added.
(7) Ploughing on dry soil to speed up infiltration and allow rainwater to drain the harmful ingredient.
