What are Macronutrients?

Fertilizer

A fertilizer is a substance containing one or more of the essential plant elements that, when added to a soil or plant system, aids plant growth and/or increases productivity by providing additional essential elements for plant use. Fertilizer application increases the ability of the soil to supply essential plant nutrients in adequate amounts and proportions for plant growth and reproduction in the absence of toxic substance which may inhibit plant growth.

Crop yield

Crop yield is the measure of crop produced per area of land and is one of the metrics used to determine the efficiency of food production. . It’s an important metric to understand as it helps us understand food security and explains, for example, the reason your tomatoes cost more one year and less the following year.

When considering crop yield, it is always important to understanding the following aspects:

The nature of your soil
The source of your inputs
The application rate of inputs and efficacy
Where you acquired your agronomical advice

What are Macronutrients?

Macronutrients are essential for plant growth and good overall plant health. The primary macronutrients are Nitrogen (N), Phosphorus (P), and Potassium (K) and are the commonly included elements in a wide range of fertilizers.

Leaves of corn plant with nitrogen deficiency. The leaves exhibit V-shaped yellowing starting from the tip and progressing down the midrib towards the base of the leaf.

Nitrogen (N)

Nitrogen is essential for plant development, since it plays a fundamental role in energy metabolism and protein synthesis. Nitrogen is absorbed by the plant in the form of a nitrate. This macronutrient is directly related to plant growth. It is indispensable for photosynthesis activity and chlorophyll formation.

Nitrogen is involved, above all, in the aerial zone, the part of the plant that a person sees. It promotes cellular multiplication. Nitrogen deficiency results in a loss of vigor and color. Growth is slowed and leaves die off, starting at the bottom of the plant.

The photo to the right shows typical symptoms of nitrogen deficiency:

Phosphorus (P)

Leaves of corn plants with phosphorus deficiency exhibiting reddish-purplish leaf tips with margins.

Phosphorus is involved in the stimulation of root growth and flowering. Although phosphorus is also necessary during the plant’s growth period, it is much more involved in the flowering stage. Phosphorus is involved in transporting and storing energy. It improves the plant’s general state and increases the plant’s ability to withstand adverse climatological conditions. Phosphorus is essential in organic compound formation and the correct execution of photosynthesis. A shortage of phosphorous results in a late, deficient flowering, browning and wrinkling of the leaves, older leaves showing a purple pigmentation and a lack of vigour in general. Root interception and the abundance of root hairs will significantly increase the opportunity for Phosphorus absorption. There is the need to use seed inoculant such Eco-T to treat seeds before planting. This will help the better seed germination and better root development which will enhance Phosphorus absorption and thereby increasing crop yield.

The photo to the right shows typical symptoms of phosphorus deficiency:

Leaves of corn plants with potassium deficiency are yellowish green in colour, with yellowing starting from the tip of the leaves and progressing along the edges towards the base of the lower leaves.

Potassium (K)

Potassium is involved in the regulation of water and the transport of the plant’s reserve substances. It increases photosynthesis capacity, strengthens cell tissue, and activates the absorption of nitrates. Potassium is involved in the opening and closing of the stomata of leaves. Potassium stimulates flowering and the synthesis of carbohydrates and enzymes. This, in turn, provides an increase in the plant’s ability to withstand unfavorable environments such as low temperatures, and prevents withering. Therefore, a lack of potassium reduces plant resilience to dry spells and frosts or to a fungus attack. This, in turn, results in a lack of balance among other nutrients, such as calcium, magnesium, and nitrogen. When there is a potassium insufficiency, dark spots appear on the leaves.

The photo to the right shows typical symptoms of potassium deficiency:

Secondary Macronutrients

Secondary macronutrients are also essential, although they are consumed in smaller quantities than the primary macronutrients: N, P, and K. The secondary macronutrients are Calcium (Ca) Magnesium (Mg) and Sulfur (S).

Calcium (Ca)

Calcium attaches to the walls of plant tissues, stabilizing the cell wall and favoring cell wall formation. Calcium is also involved in cell growth and development. It improves plant vigor, activating the formation of roots and their growth. Calcium contributes to mineral retention in the soil and to the transportation of such minerals. It neutralizes toxic substances in plants and contributes to seed formation. Calcium stabilizes and regulates several different processes, while calcium insufficiency causes yellow and brown spots on the leaves, and slows plant growth in general.

The photos to the right show typical symptoms of calcium deficiency with chlorosis beginning in the leaf edges and moving inward, resulting in wrinkled older leaves, dead stem tips and tomato fruits with blossom end rot (BER)

Magnesium deficient leaves curl along the edges showing a whitish colour.

Magnesium (Mg)

Magnesium constitutes the core of the chlorophyll molecule and is therefore essential for photosynthesis. This makes it an indispensable element for plant development. Magnesium promotes the absorption and transportation of phosphorus. It contributes to the storage of sugars within the plant. Magnesium performs the function of an enzyme activator, and in fact activates more enzymes than any other nutrient. Magnesium deficiencies result in weak stalks, loss of greenness in the oldest leaves, and the appearance of yellow and brown spots, even though the leaf veins remain green.

The below photo shows typical symptoms of magnesium deficiency:

Sulfur deficiency displaying similar symptoms to nitrogen deficiency -stunted appearance young leaves are light green with lighter colour vein.

Sulfur (S)

Sulfur participates in the formation of chlorophyll. It is necessary for performing photosynthesis and intervenes in protein synthesis and tissue formation. Sulfur is fundamental in the metabolizing of nitrogen, since it improves nitrogen efficiency. Sulfur also improves plant defenses in general. A shortage of sulfur is rare, but when it does occur, the plant becomes lighter in color, taking on a pale green appearance. A general chlorosis is seen, similar to what occurs with nitrogen deficiency.

The photo to the right shows typical symptoms of sulfur deficiency:

Plant Nutrition

In plant nutrition, it is important there is no deficiency in primary or secondary macro elements or in essential microelements. Moreover, these elements must be present in the proper proportions. A plant is unable to complete its life cycle in the absence of each of these mineral elements. Essential nutrients are mineral nutrients crucial for plant growth, and the function of one element can not be replaced by another. These elements are directly involved in plant metabolism, and elimination of any will cause plants to display abnormalities of growth and deficiency symptoms. The 18 elements considered to be essential for plant nutrition are shown below

Major essential nutrients:

C, H, O – absorbed as gases. Carbon and Oxygen from atmospheric fixation in photosynthesis. Hydrogen and Oxygen from water hydrolysis.

N, P, K, Ca, Mg, S – Macro elements. Absorbed from soil solution. Needed in high ratio, their concentration in tissue is measured by percentages.

Fe, Mn, Zn, Cu, Mo, B – Micro elements. Absorbed from soil solution needed in small quantities, their concentration in tissue is measured in ppm.

B – have a very narrow range of efficiency and even slight increase in concentration will cause damages (0.5 ppm in soil solution).

Cl, Na – “Damaging nutrients”. Regularly existent in sufficient quantity in soil and in arid areas even in excess. The plant need small quantities from them and excess will damage soil structure and plant tissue.

Crop Nutritional Monitoring:

At Demeter Ghana we work throughout the growing season, monitoring crop needs for water and nutrients, and advising your irrigation and fertilizer regime accordingly.. With such monitoring we help you achieve sustainable agricultural practices through minimization of leaching or harm to the soil structure. The result is: