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Plants need nutrients and minerals to thrive. These chemical elements are essential for their growth, metabolic functioning, and completion of their life cycle. Plants absorb carbon (C), hydrogen (H), and oxygen (O) from the air. The remaining essential elements are absorbed from the soil or through the externally amended fertilizers.
Soil is a major nutritional source for plants. Macronutrients are consumed by the plant in large quantities whereas micronutrients are needed in smaller quantities. Micronutrients are also known as trace elements because they are only needed in very small amounts by the plant. Nitrogen (N), phosphorus (P), potassium (K), calcium (C), sulfur (S), and magnesium (Mg) are known as macronutrients, whereas, boron (B), chlorine (Cl), manganese (Mn), iron (Fe), zinc (Zn), copper (Cu), molybdenum (Mo), and nickel (Ni) are known as micronutrients.
Plants take in these essential minerals from the earth's surface after various physical, chemical, and biological weathering processes. These physical and biological processes depend on several factors, such as climatic conditions and mineral properties. There are many mineral sources, for example, K-feldspars, micas, and illite. These are promising sources of potassium, and they also contain other minerals such as Mg, Fe, Ca, Na, Si, and a number of micronutrients. Mineral sources like amphiboles and pyroxenes are considered as important reservoirs of Mg, Fe, Ca, Si, and most of the micronutrients.
The effects of mineral nutrients on plant growth are complex and the list of minerals and their vital roles in plant development are given below.
Nitrogen (N): Nitrogen is a vital element in plant growth. It is found in all plant cells, plant proteins, hormones, and chlorophyll. Leguminous plants fix atmospheric nitrogen in their roots which is then utilized for various plant processes.
Phosphorus (P): Phosphorus can transfer energy from sunlight to plants. It initiates early root and shoot growth and hastens maturity. Phosphorus also acts as an indicator mineral because mycorrhizae and other specific microbes can only convert inorganic phosphate to its usable form.
Potassium (K): Potassium increases the vigor and disease resistance of plants. It helps to produce and transport starches, sugars, and oils to various parts of the plant body. Potassium can also improve the quality of fruits.
Calcium (Ca): Calcium is essential for the development of roots and leaves.
Magnesium (Mg): Magnesium is a key component of chlorophyll. Chlorophyll is a plant pigment, which imparts the green color to the plant and plays a vital role in photosynthesis. Magnesium is considered as an indicator for healthy plants.
Sulfur (S): Plant proteins are made up of sulfur-containing amino acids. These proteins are involved in the energy-producing processes in plants. It is also responsible for many flavors and odor compounds such as the aroma of onions and cabbage.
Iron (Fe): Iron is a constituent of many compounds that regulate and promote plant growth.
Manganese (Mn): Manganese is involved in plant photosynthesis.
Coper (Cu): Copper is an essential constituent of enzymes in plants.
Zinc (Zn): Zinc helps in the production of the plant hormones responsible for stem elongation and leaf expansion.
Boron (B): Boron helps with the formation of cell walls in rapidly growing tissue.
Molybdenum (Mo): Molybdenum helps bacteria and soil organisms convert nitrogen in the air into soluble nitrogenous compounds in the soil. This is particularly needed by leguminous plants. It is also essential in the formation of proteins from soluble nitrogenous compounds.
Gary Zimmer, the co-author of Advancing Biological Farming, stated that modern agriculture depends upon our ability to cycle minerals that are nutritionally important, through crops, poultry, and animals. In particular, the absorption of these minerals by green plants and their subsequent role in the formation of organic compounds is key to almost all forms of life. Soil plays an absolutely indispensable role in this regard as it is the most vital source of these minerals for the plants.