(3) Nutrients

      3.1 Nutrient Cycles: Global Recycling

                          Nutrient cycles describe the flow of nutrients in and out of stores as a result of biotic and abiotic processes. Without human interference, nutrient cycles are almost perfectly balanced. Nutrients are recycled by global cycles through the earth’s air, land, water, and living organisms. Nutrients are the elements that are essential to living, grow and reproduce of organisms.

3.2 Nutrients

                        All of the essential elements are by required for plant growth and completion of the plant life cycle from seed to seed. Some essential elements are needed large quantities and others in much smaller quantities. However, from a practical standpoint, three of the six essential macronutrients are most often "managed" by the addition of fertilizers to soils, while the others are most often found insufficient quantities in most soils and no soil amendments are required to supply adequate supplies.

           

  3.3 Categories of nutrients

         Nutrients in soils are can be divided into two categories as macronutrients and micronutrients. Macronutrients are also can be divided into two categories as primary nutrients and secondary nutrients.

3.2.1 Macronutrients

Macronutrients are those elements and compounds needed in large quantities for a plant to grow.

3.2.1.1 Primary nutrients

                   These major nutrients usually are lacking from the soil first because plants use large amounts for their growth and survival.

  Ex: N, P and

3.2.1.2 Secondary nutrients

                    There are usually enough of these nutrients in the soil so fertilization is not always needed.

 Ex: Ca, Mg and S

3.2.2 Micro nutrients

                    Micro-nutrients are those elements essential for plant growth which are needed in only very small (micro) quantities and are sometimes called minor elements or trace elements.

Ex: B, Cu, Fe, Mn, Mo, Zn, and Cl