ESSENTIAL ELEMENTS IN PLANT NUTRITION
Seventeen elements are found to be essential for normal plant growth and reproduction. With the exception of carbon, hydrogen and oxygen (supply from the atmosphere), all other essential elements are obtained from the soil
Essential elements can be grouped into four categories based on their origin or the relative amount a plant needs in order to develop properly. Non mineral essential elements are derived from the air and water. Primary essential elements are most often applied through commercial fertilizers or through manures. Secondary elements are normally applied as soil amendments or are components of fertilizers that carry primary nutrients. Non mineral, primary and secondary elements are also referred to as macronutrients since they are required in relatively large amounts by plants. Micronutrients are required in very small, or trace amounts by plants. Although micronutrients are required by plants in very small quantities, they are equally essential to plant growth.