Light, Water, Nutrients Voila!
Numerous elements are required for proper plant growth. Air and water supply some of these elements including carbon (C), hydrogen (H) and oxygen (O), while soil is the principle source of all other nutrients. Plant roots must mine the soil in order to find these much-needed macro and micro nutrients.
These are plant nutrients used in the largest amounts. The primary macronutrients include Nitrogen(N), Phosphorus (P) and Potassium (K). Secondary macronutrients, are used in lesser amounts and include Calcium (Ca), Magnesium (MG) and Sulfur (S).
These are plant nutrients used in the smallest amounts and include: boron (B), copper (Cu), chlorine(Cl), manganese (Mn), molybdenum (MO), iron (Fe) and zinc (Zn). Even though these nutrients are used in trace amounts, the omission of even one will cause plants not to grow and reproduce. In this way, they are just as important as macronutrients. Care is needed when applying micronutrients because the difference between deficiency and toxicity is often minuscule.
Roots take up hydrated ions. These ions may be cations (positively charged) or anions (negatively charged). Many of the components that make up soil aggregates are negatively charged, and therefore, attract cations while anions tend to leach from the soil. The CEC (cation exchange capacity) is the measurement of the soil’s ability to hold onto cation nutrients.
Because nutrients enter into a plant as ions, they have varying degrees of mobility within the plant. The location of nutrient deficiency symptoms partly depends on the mobility of that nutrient. A mobile nutrient deficiency will exhibit symptoms in the older leaves because it is able to travel to where it is needed most- new growth. While an immobile nutrient will show signs of deficiency in newer foliage because it is locked up in the older growth.