Plants need the right combination of nutrients to live, grow and reproduce. When plants suffer from malnutrition, they show symptoms of being unhealthy. Too little or too much of any one nutrient can cause problems. Plant nutrients fall into 2 categories: macronutrients and micronutrients. Macronutrients are those elements that are needed in relatively large amounts. They include nitrogen, potassium, sulfur, calcium, magnesium and phosphorus. Micronutrients are those elements that plants need in small amounts (sometimes trace amounts), like iron, boron, manganese, zinc, copper and molybdenum. Both macro- and micronutrients are naturally obtained by the roots from the soil. Thus, nutrients may be physically present in the soil, but not available to plants. A knowledge of soil pH, texture, and history can be very useful for predicting what nutrients may become deficient and if leaf application of fertilizers and biostimulants may be necessary to ensure the optimal growth and development rate.
Yield and the quality of products from crops are strongly linked to the supply of nutrients through fertilizers product. However, nowadays sustainable fertilization management is essential to increase the overall performance of cropping systems by providing economically optimum nourishment to the crop while minimizing nutrient losses and supporting agricultural system sustainability by increasing Nutrient Use Efficiency (NUE). Plant biostimulants represent a promising strategy to boost sustainable agricultural production thanks to their capacity of improving directly or indirectly nutrient use efficiency of crops especially under low nutrient availability which it means that with biostimulants it is possible to apply less fertilizers. Biostimulants allow to reduce the supply of fertilizers while safeguarding the yield and profitability for the farmer.
NITROGEN
Main Functions
Nitrogen promotes leaves, stem and other vegetative part’s growth and development. It stimulates root growth. N produces rapid early growth and increases protein content of fodder crops.
Common Deficiencies
General yellowing of older leaves (bottom of plant). The rest of the plant is often light green.
PHOSPHORUS
Main Functions
Phosphorus is essential in photosynthesis and respiration. P aids in root development, flower initiation, and seed and fruit development.
Common Deficiencies
Leaf tips look burnt, followed by older leaves turning a dark green or reddish-purple.
POTASSIUM
Main Functions
Potassium helps photosynthesis, regulates the water status in the plant and plays an essential part in the formation of starch and in the production and translocation of sugars. K enhances fruit quality.
Common Deficiencies
Older leaves may wilt, look scorched. Interveinal chlorosis begins at the base, scorching inward from leaf margins.
CALCIUM
Main Functions
Calcium has a main role as structural nutrient in the plant, playing a core role in the stability of cell walls and cell membranes. Calcium prevents sensitive calcium physiological disorders, in many crops. It is fundamental for fruit quality; it improves fruit firmness and fruits shelf-life.
Common Deficiencies
New leaves (top of plant) are distorted or irregularly shaped. Causes tip burn, blossom-end rot, bitter pit and fruit cracking.
MAGNESIUM
Main Functions
Magnesium is a major constituent of the chlorophyll molecule, and it is therefore actively involved in photosynthesis. It aids phosphate absorption and translocation. Mg facilitates translocation of carbohydrates (sugars and starches) and enhances the production of oils and fats.
Common Deficiencies
Older leaves turn yellow at edge leaving a green arrowhead shape in the center of the leaf.
SULFUR
Main Functions
Sulfur is actively involved in metabolism and in the synthesis of oils, especially in oil crops and has a synergistic effect on the synthesis of aromatic precursors, the thiols in white and rosé wine. S aids in seed production, chlorophyll formation, nodule formation in legumes, and stabilizing protein structure.
Common Deficiencies
Younger leaves turn yellow first, sometimes followed by older leaves.
IRON
Main Functions
Iron is crucial for metabolic processes such as respiration and photosynthesis as well as for biosynthesis of fundamental molecules like chlorophyll. It is also essential for nitrogen and sulfur assimilation.
Common Deficiencies
Yellowing occurs between the veins of young leaves.
BORON
Main Functions
Boron is essential for cell division, it helps with pollination, fruit and seed development. Other functions include translocation of sugars and carbohydrates, nitrogen metabolism, regulation of hormone levels and transportation of potassium, which helps regulate internal water balance. Since B helps transport sugars, its deficiency can reduce the attraction and colonization of mycorrhizal fungi.
Common Deficiencies
Terminal buds die, witches’ brooms form.
ZINC
Main Functions
Zinc is a key component of many proteins and enzymes. It is used in the formation of chlorophyll and some carbohydrates, conversion of starches to sugars and its presence in plant tissue helps the plant to withstand cold temperatures. Zn contributes to growth hormone production and stem elongation.
Common Deficiencies
Terminal leaves may be rosetted, and yellowing occurs between the veins of the new leaves.
COPPER
Main Functions
Copper is essential in several plant enzymes with several properties and functions. Cu is necessary for chlorophyll formation, and it also has a primary role in carbohydrate and protein metabolism.
Common Deficiencies
Leaves are dark green, plant is stunted.
MANGANESE
Main Functions
Manganese has primarily functions as part of the plant enzyme system, activating several metabolic functions. Mn is essential for photosynthesis metabolism. It affects nutritional quality, strength, and stiffness of plant tissues, being involved in the synthesis of valuable components such as ascorbic acid (vitamin C) and lignin.
Common Deficiencies
Yellowing occurs between the veins of young leaves. Pattern is not as distinct as with iron. Reduction in size of plant parts (leaves, shoots, fruit) generally. Dead spots or patches.
MOLYBDENUM
Main Functions
Molybdenum is a necessary component for nitrogen assimilation and therefore favor the synthesis of amino acids and proteins. It is also an essential element for chlorophyll synthesis. In legumes, Mo helps in the fixation of atmospheric nitrogen by the root nodule bacteria.
Common Deficiencies
General yellowing of older leaves (bottom of plant). The rest of the plant is often light green
