Plants need sixteen nutrients for development. The 3 non mineral nutrients are hydrogen (H), oxygen (O) and carbon (C). These nutrients are in the air and the water. In a procedure that is called photosynthesis, the plants use energy from the sun in order to turn the carbon dioxide (CO2) and water (H2O) in sugars and amylum (amylum and sugar are animals’ food). The rest thirteen nutrients are coming from the soil.
Soil nutrients are divided in two categories according to the quantities that plant need: macro elements and microelements. The macro elements are nitrogen, phosphorus, potassium, calcium, magnesium and sulphur. The trace elements are iron, manganese, boron, zinc, copper, molybdenum and chlorine. These are the essential nutrients that are essential for plant development. Plants will grow till they start to have deficiency of one or two nutrients. Then, the growth will not continue due to their deficiency. If the nutrients are deficient or plentiful, then plants will be disformed and will have tainted color. Several symptoms in plants show the deficiency for nutrients, even though the symptoms differ each other. The yellow leaves for example can be caused by one or more deficiencies of nutrients.
More specifically:
Nitrogen (N)
Nitrogen is the chemical element that we can find on plant cells as food storage. It is the basic element of other organic compounds as Chlorophyl, Aminoacids and some plant hormones. The Nitrogen metabolism is the main factor for the development of leaves (plant growth). The exaggerated presence of Nitrogen has a result the blossom delay. The Nitrogen absence has as a result yellow leaves and the limited growth of new sprouts.
Potassium (K)
Potassium is the essential nutrient for crop development:
• Improves the taste, resistance and organoleptic crop characteristics
• Optimizes the energy of the sun in photosynthesis
• It regulates the opening and closing of stomata
• It regulates the water balance
• It increases crop resistance during cold period or drought
• It regulates pH as eliminating organic acids
• It makes possible the activation of several enzymes that interfere to:
• Composition of sugars
• Nitrogen absorption
• Cellular respiration
Phosphorus (P)
Phosphorus is an important element for flowering and fruitfulness
Its main functions are:
• Interferes during the synthesis of proteins, sugars, lipids, chlorophyl, carboxylic acids
• Activates the transfer of nutrients as it stimulates the enzymes that are responsible for transport of sugars through the tissues
• It stimulates cellular division
One other function of phosphorus is that it allows the energy transfer since it enables synthesis of molecules, such as ATP, AMP, ADP, NADP, FAD, COASH, LIPS, UDP, TPP, PAL... that give rise to the activation of several reactions of plant metabolism.
Calcium (Ca)
Existence of Calcium at leaves is important since it is a structural cell element and helps the water circulation into plant cells. Some plants have calcium in order to absorb nitrogen and other metals. Its deficiency will give feeble stems, the leaves will turn to yellow ones or will have yellow edges.
Iron (Fe)
It is essential for chlorophyl synthesis. It is an important element for growth parts of the leaves. Its deficiency is appearing when leaves turn to yellow. If pH is alkaline, then iron is not absorbed by the plants.
Manganese (Mn)
Manganese is the essential micro element for plants since:
• It promotes synthesis of chlorophyl (allowing photolysis of H2O during photosynthesis)
• It favors nitrogen in various metabolic paths
• It increases the content in coloring compounds as carotenoid or lutein. Afterwards, these ones, are flavonoid molecules (polyphenols), with antioxidant action.
Zinc (Zn)
Zinc is an essential microelement for the plants, since it:
• Catalyzes the phenolic compounds in order to allow the synthesis of auxins. So, it is essential for the growth of buds (elimination of Zn usually results in small leaves)
• Favors the absorption of nitrogen, allowing the synthesis of the most important aminoacids for the plants
Stimulates the enzymatic action
• Zinc and Copper are consisting a part of certain enzyme that is called “superoxide dismutase”, which is responsible for the metabolism of free roots of O2, and so it prevents the plant oxidation
Zinc is the essential micro element for the plants since it is an essential component of numerous enzymes. During the flowering stage, it interferes to the metabolism of nitrogen, to the regulation of growth and to the synthesis of auxin.
Therefore, is irreplaceable, in order to avoid the formation of the fall, the cutting of the flowers and enhance the improvement of flowering and fruit setting in the crops.
Copper (Cu)
Copper is a microelement which consists part of fundamental enzymes for plant metabolism, such as:
- Polyphenol oxidase
- Laccase
- Diamine Oxidase
It catalyzes the oxidation of polyamines, which consist a kind of growth regulator that allows the plant resistance when it faces stress condition, including those ones that result from the attack of pathogens.
The copper favors the metabolism of phenolic compounds and therefore it increases plant resistance against attack of pathogens.
Copper (Cu) consists one of the most bio stimulant elements able to induce synthesis of phytoalexins to the plants.
Phytoalexins are phenolic molecules that are created by the plant as a mean of self-defense of phytopathogens (fungi, bacteria, virus, parasites) or after stress condition.
Moreover, copper has more functions: it takes part to the metabolism of nitrogen, cellular respiration and photosynthesis.
Boron (B)
Boron is essential for the division and cell growth, playing a basic role in meristematic function, especially in the process of cellular division. For this reason, it is an essential element for crop growth. Also, it enables the transfer of carbohydrates (sugars) through plant tissues.
Chlorine (Cl)
The movement of water to the cells as also photosynthesis is depending to chlorine existence. Exaggerate existence of chlorine, in some plants will cause increased level of toxicity. Its deficiency has a result the wilting of leaves and the creating of shorter roots.
Let’s not forget that all essential nutrients have the same value for plant growth. Plant growth depends on the less available nutrient (binding factor) and not from the total quantity of available factors (“Justus von Liebig's Law”). For this reason, this law is shown with a barrel, where each board is shown with a different height. Each board represents one element essential for the plant. The content of barrel is determined from the board with the short height, so the element with the less availability is the one that determines the crop yield.
Generally, in order a cultivation to be sustainable, fertilizer should be applied with a rational way. This means that maximum absorption of nutrients should be assured, minimizing the losses in the environment (with vaporization, runoff or leaching of fertilizers). The appropriate ways to achieve the above are the soil analysis and leaf diagnosis.
Target of soil analysis is the definition of soil composition, of nutrients and other characteristics as pH and conductivity. These measurements give the ability to predict the growth of a cultivation in the soil after necessary improvements. The soil analysis gives to the farmer the ability to have best results with the most economical way, in short and in long term.
On the other side, the leaf diagnosis is a procedure to determine the concentration of nutrients in the leaves and reflects the nutrional condition of the crop.
The analysis of the leaves can indicate the existence of nutritional problems and to prevent the appearance of deficiency symptoms of one or more nutrients.