Under natural forest conditions, the annual decomposition of leaves, needles and twigs provide a fresh resource of minerals for tree and shrub use. Landscape trees grown in lawns and driveways usually do not have this nutrient source and are in need of additional minerals since landscape debris is routinely hauled away.
Sixteen chemical elements are known to be important to a plant’s growth and survival. The first of these are carbon (C), hydrogen (H) and oxygen (O), which plants acquire in sufficient quantities from the air and water. The other 13 mineral nutrients, are acquired by plant roots, which absorb soil minerals dissolved in water. The required mineral nutrients are divided into two groups: macronutrients and micronutrients.
The primary macronutrients are nitrogen (N), phosphorus (P), and potassium (K). These major nutrients are usually lacking from the soil first because plants use large amounts for their growth and survival. The secondary macronutrients are calcium (Ca), magnesium (Mg), and sulfur (S). Fertilization with these nutrients is not always needed.
Micronutrients are nutrients needed needed in only very small quantities . The micronutrients are boron (B), copper (Cu), iron (Fe), chloride (Cl), manganese (Mn), molybdenum (Mo) and zinc (Zn). Southern Idaho soils can be deficient in S, Fe, Mn, and Zn.