Nutrients play a very important role in the growth and development of plants. The growth and development of Plants depends on nutrients derived from soil or air, or supplemented by the use of fertilizers.

The soil supplies most of the nutrients needed by plants. Plant growth is limited when there is an insufficient supply of these nutrients. In natural conditions, nutrients are recycled from plants to soil to meet plant needs. However, agricultural crops may require more nutrients than natural vegetation.

Large amounts of nutrients are also removed in harvested crops. Optimal crop growth and profitability may require fertilization with inorganic fertilizers, animal manures, green manures, or legume management.

Nutrient requirements for plants keep increasing as the plant grows.  Nutrients available in the soil are the primary source of nutrients for plants while organic or in-organic nutrient fertilizers are the secondary source of nutrients.

 Organic and in organic fertilizers are applied to plants to ensure that the plants get enough nutrients. Crop production and growth can be impacted negatively if the nutrients are in excess or if the nutrients are deficient. Many deficiencies of nutrients in plants can be recognized by observing plant leaves.

Plants require 17 essential elements found in nature to properly grow and develop. These elements are Carbon, hydrogen, and oxygen which are derived from the atmosphere and soil water. The remaining 15 essential elements, nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, iron, zinc, manganese, copper, boron, molybdenum, and chlorine, and Nickel are supplied either from soil minerals and soil organic matter or by organic or inorganic fertilizers.

Each type of plant is unique and has an optimum nutrient range as well as a minimum requirement level. Below this minimum level, plants start to show nutrient deficiency symptoms. Excessive nutrient uptake can also cause poor growth because of toxicity. Therefore, the proper amount of application and the placement of nutrients is very important.

Carbon (C), Hydrogen (H), and Oxygen (O) are utilized within the plant physical structure. These elements, obtained from the air (CO2) and water (H2O), are the basis for carbohydrates such as sugars and starch, which provide the strength of cell walls, stems, and leaves, and are also sources of energy for the plant and organisms that consume the plant.

The 17plant element are grouped into elements that are required in large quantities which are called Macro Nutrients and elements required in very small quantities which are called Micro Nutrients. 

Macro Nutrients are classified as Primary Macro Nutrients which include Nitrogen (N), Phosphorus (P), and Potassium (K) and secondary Macro nutrients which include calcium (Ca), magnesium (Mg), and sulfur (S). These elements contribute to plant nutrient content, function of plant enzymes and biochemical processes, and integrity of plant cells.  Deficiency of these nutrients contributes to reduced plant growth, health, and yield; thus, they are the three most important nutrients supplied by fertilizers.

Micro Nutrients are used in small quantities by the plant, but nevertheless are necessary for plant survival.  These micronutrients include iron (Fe), boron (B), copper (Cu), chlorine (Cl), Manganese (Mn), molybdenum (Mo), zinc (Zn), and nickel (Ni).

Description of the plant nutrient and deficiency symptoms:

Nitrogen (N)

Promotes rapid vegetative growth and gives plants healthy green color.

Deficiency symptoms are stunted growth, pale, yellowish color, burning of tips and margins of leaves starting with older leaves at the lower section of the plants.

Phosphorus (P)

Stimulates early growth and root formation, hastens maturity, promotes seed production and makes plants hardy.

Deficiency symptoms small root growth, spindly stalk, delayed maturity, purplish discoloration of leaves, dying of tips of older leaves, and poor fruit and seed development.

Potassium (K)

Improves plant’s ability to resist disease and cold, aids in the production of carbohydrates.

Deficiency symptoms slow growth, margins on leaves develop a scorched effect starting on the older leaves, weak stalk, shriveled seed or fruit.

Calcium (Ca)

It aids in the movement of carbohydrates in plants, essential to healthy cell walls and root structure.

Deficiency symptoms Terminal bud dies under severe deficiency, margins of younger leaves scalloped, blossoms shed prematurely, weak stalk or stem structure.

Sometimes Calcium deficiency is triggered not by the absence of Calcium but inadequate or insufficient watering.

Magnesium (Mg)

It is an ingredient of chlorophyll, aids in the translocation of starch within the plant, essential for formation of oils and fats.

Deficiency symptoms Yellowing of leaves between veins starting with lower leaves which are older, leaves abnormally thin, tissue may dry and die, leaves have tendency to curve upward.

Sulfur (S)

It helps in the formation of oils and parts of protein molecules.

Deficiency symptoms young leaves light green to yellowish in color. In some plants older tissue may be affected also. Small spindly plants, retarded growth and delayed maturity. Interveinal chlorosis on some plant’s leaves.

Boron (B)

It helps  in the assimilation of calcium amount required is extremely small.

Deficiency symptoms Death of terminal growth, causing lateral buds to develop and produce a witch’s broom effect. Thickened, curled, wilted and chlorotic leaves. Soft or neurotic spots in fruit or tubers. Reduced flowering or improper pollination.

Copper (Cu)

Promotes formation of Vitamin A, excess is very toxic.

Deficiency symptoms Stunted growth, dieback of terminal shoots in trees, poor pigmentation, wilting and eventual death of leaf tips, formation of gum pockets around central pith in oranges.

Manganese (Mn)

It serves as an activator for enzymes in growth processes, assist iron in chlorophyll

formation, generally required with zinc in foliar spraying of citrus.

Deficiency Symptoms Interveinal chlorosis of young leaves, gradation of pale color next to veins.

Zinc (Zn)

It is an essential constituent of several enzymes, controls synthesis of indoleacetic acid – an important growth regulator. The micronutrient most often needed by western crops- trees, grapes, beans, onions, tomatoes, cotton rice.

Deficiency symptoms is leaf chlorosis resulting in yellowing between the veins of the leaves. Decreased stem length and rosetting of terminal leaves. Reduced fruit bud formation.

Molybdenum (Mo)

Required for Nitrogen utilization, needed to transform non protein Nitrogen  into amino acids, and legumes cannot fix atmospheric Nitrogen symbiotically without Molybdenum.

Deficiency Symptoms includes Stunting and lack of vigor, very similar to Nitrogen deficiency due to the key role Molybdenum plays in Nitrogen utilization.

Chlorine (Cl)

Required in photosynthetic reactions of plants. Deficiency is not seen in the field due to its universal presence in nature.

Deficiency symptoms Wilting, followed by chlorosis. Excessive branching of lateral roots. Bronzing of leaves, chlorosis and necrosis in some plants.

Iron (Fe)

Function Essential for formation of chlorophyll, releases energy from sugars and starches.

Deficiency symptoms are yellowish or white leaves (young leaves first), veins green, affected leaves curl up.

Nickel (NI)

Necessary for proper functioning of the enzyme know as urease, and found to be necessary in seed germination

Deficiency Symptom; One common Ni deficiency symptom across plant species is the necrosis of leaf tips due to the accumulation of urea to toxic concentrations.

The table below lists the essential Macro Nutrients and their Mobility in soil and plants.

The table below lists the essential Micro Nutrients and their Mobility in soil and plants.

FERTILIZER TYPES

Plant fertilizers can be classified into Organic or In Organic fertilizers

Organic fertilizer are fertilizers that are derived from organic sources, including organic compost, cattle manures, poultry droppings and domestic sewage. organic fertilizers are natural, since the nutrients they possess are only from plant or animal-based materials. Either end products or byproducts of natural processes. Organic fertilizers work over time to create a healthy growing environment. Examples of organic fertilizers are Poultry droppings, Cattle dung, Rabbit droppings, Rabbit urine, domestic sewage, goat droppings, horse droppings etc. Organic fertilizers need to be composted very well to ensure that they will not harm plants.  Well composted chicken manure is one of the best soil applied organic manure available.

In-organic fertilizer is synthetic, comprised of synthetic chemicals and minerals. In organic fertilizers provide rapid nutrition to plants and they can be used to correct plant deficiencies very quickly. They are more commonly available than organic fertilizer. In-organic fertilizers can easily be developed to treat specific plant nutritional deficiencies. Examples of In-organic Fertilizers are Zinc Sulphate fertilizer, Nitrogen, Phosphorous, Potassium (N.P.K) Fertilizers, Calcium Nitrate, Potassium sulphate, micro nutrient solutions etc.  

FERTILIZER APPLICATION METHODS

Whenever you need to apply any fertilizer or plan nutrients remember to consider the four Rs. The four Rs are use the Right amount of the Right fertilizer at the Right place at the Right time.

Before considering the four Rs, a soil test needs to be performed. Soil tests assess the current nutrient status of the soil and indicate whether these levels are sufficient for crop production. If adequate amounts of nutrients are present in the soil, the right amount to apply is none.

If the soil tests results shows that there are some nutrient deficiencies, there will be a rate recommendation. This is the right amount. The right time and right place depend on site-specific agronomic factors accounting for crop biology and growth stage, and current environmental conditions. Follow the best management practice appropriate for your situation.

SOIL PH

Soil pH is a measure of the acidity and alkalinity in soils. pH levels range from 0 to 14. The optimal pH range for most plants is between 5.5 and 7.0.

Soil pH is not a nutrient, but it determines the availability of nutrients to your plants The presence of nutrients in the soil does not mean that your plants will be able to make use of the nutrients and thrive. The nutrients must be available to your plants, and, to be available, they must be soluble. They will not be soluble if the soil pH is a mismatch for the plant.

Some plants love acidic soils while some plants like alkaline soils.  A  soil is said to be acidic if it has a PH of 4 to 6.5  while a soil is said be alkaline if it has a PH of 7.5 to 9. A soil is said to be neutral if the PH is 7.

Soil PH is measured using a Soil PH meter. Soil PH can be changed by the application of fertilizers/

Fertilizers either organic or in-organic are applied by different methods, below are the most common methods of fertilizer application to plants.

Solid Fertilizers

1, Broadcast

Broadcast Fertilization means a fertilizer application technique where fertilizer is spread across the soil surface. The main objectives of broadcasting the fertilizers at sowing time are to uniformly distribute the fertilizer over the entire field and to mix it with soil.

2, Placement

Fertilizers are placed in the soil before sowing irrespective of the position of the seed. Placement of fertilizers is normally adopted when the quantity of fertilizers to apply is small, development of the root system is poor, soil have a low level of fertility and to apply phosphatic and potassic fertilizer.

3, Band Placement

Band application is also known as starter application. Fertilizer is applied in bands near where developing roots will easily reach it; either to the side and below the seed rows, slightly below the seeds, or in between rows.

Liquid Fertilizers

1, Foliar feeding

Foliar feeding is a technique of feeding plants by applying liquid fertilizer directly to the leaves, this is typically done by using a sprayer to apply the liquid fertilizer on both sides of the leaves. Plants are able to absorb essential elements through their leaves. The absorption of the fertilizer nutrients takes place through their stomata and also through their epidermis.

2, Fertigation

Fertigation is the practice of applying fertilizer solutions with irrigation water, typically through a micro sprinkler or a drip system.