There are 16 essential elements for plant growth. Research has shown plants require the presence of each of these 16 elements at some time to complete their life cycle.
Categorically these elements are grouped as structural, macro, secondary, and micro. Structural elements are carbon (chemical symbol of C, with an approximate 45% content), oxygen (O, 45% and hydrogen (H, 5%) which constitute 90% — 98% of the dry matter. Plants acquire these elements from air and water, so little management is necessary.
Macro elements are nitrogen (N, 1% — 5%), phosphorus (P, 0.1% — 1%) and potassium (K, 0.5% — 3%) constituting around 1% — 8 % of the dry matter.
Research has shown these elements are most likely to be deficient in most soils and that's why they're included in common fertilizer nutrients. Secondary elements are calcium (Ca, 0.1% — 1%), magnesium (Mg, 0.1% — 0.5%), and sulfur (S, 0.1% — 1%) constituting 0.3% — 2.5% of the dry matter.
Research has shown most normal soils are sufficiently supplied with secondary elements, so special management is not needed. Calcium and magnesium are more than adequately provided for plant growth through their role in regulating soil pH. Sulfur may be supplied in a supplementary format with sources of ammonium sulfate, super phosphate, and/or potassium sulfate or as gypsum (calcium sulfate).
Micro elements are iron (Fe, 10–300 ppm), manganese (Mn, 10–100 ppm), zinc (Zn, 10–100 ppm), copper (Cu, 5–50 ppm), boron (B, 5–50 ppm), molybdenum (MO, 2–20 ppm), and chlorine (Cl, 2–20 ppm) constituting “parts per million” where 1% is the same as 10,000 ppm. As with secondary elements most normal soils are sufficiently supplied with micro elements.
Triple super phosphate
Mineral nutrients found in the soil, are dissolved in water and absorbed through a plant's roots. Soil does not always provide enough of these nutrients for a plant to grow healthy. That is why many gardeners use fertilizers to add nutrients to the soil. The mineral nutrients are divided into two groups: macronutrients and micronutrients.
Macronutrients can be broken into two more groups: Primary and Secondary nutrients. The primary nutrients are Nitrogen, Phosphorus, and Potassium. These major nutrients usually are lacking from the soil first because plants use large amounts for their growth and survival.
Secondary nutrients include Calcium, Magnesium, and Sulfur. There are usually enough of these nutrients in the soil so adding these nutrients through fertilization is not always needed. Also, large amounts of Calcium and Magnesium are added when lime is applied to acidic soils. Sulfur is usually found in sufficient amounts from the slow decomposition of soil organic matter, an important reason for not throwing out grass clippings and leaves.
Micronutrients are elements essential for plant growth, but only in very small quantities. These elements are sometimes called minor elements or trace elements, but use of the term micronutrient is encouraged by the American Society of Agronomy and the Soil Science Society of America. Micronutrients are Boron, Copper, Iron, Chloride, Manganese, Molybdenum and Zinc. Recycling organic matter such as grass clippings and tree leaves is an excellent way of providing micronutrients (as well as macronutrients) to growing plants.
The best way to determine which elements you need to add to your supplemental fertilizer applications is with a soil test. Soil tests will tell you exactly what is present and what elements should be added to provide optimal growth for your garden plants.
A soil test is a process by which elements (phosphorus, potassium, calcium, magnesium, sodium, sulfur, manganese, copper and zinc) are chemically removed from the soil and measured for their "plant available" content within the sample. The quantity of available nutrients in the sample determines the amount of fertilizer that is recommended. A soil test also measures soil pH, humic matter and exchangeable acidity. These analyses indicate whether lime is needed and, if so, how much to apply.
There are 3 basic non-mineral nutrients used by plants: hydrogen (H), oxygen (O), & carbon (C). These nutrients are found in the air and water. In a process called photosynthesis, plants use energy from the sun to change carbon dioxide (CO2 - carbon and oxygen) and water (H2O- hydrogen and oxygen) into starches and sugars. These starches and sugars are the plant's food. Photosynthesis means "making things with light".