土壤是由岩石、矿物质和有机物组成的天然体. Sand, silt, clay, and organic matter help provide tilth, necessary aeration and water holding capacity, 但很少保持足够均衡的营养(植物食物)来维持植物的持续生长和提高产量. 因此，需要添加肥料来保持其肥力.
I. Primary Plant Food Elements
Nitrogen | Phosphorus | Potassium (Potash) 植物最大限度地利用这些养分，而未施肥的土壤通常无法提供最佳植物生长和产量所需的养分.
Nitrogen (N) 1. 促进快速营养生长(叶和茎)，加速应激后的恢复. 2. 在叶绿素的形成和功能中至关重要的元素, 赋予深绿色植物色的关键成分. 3. Synthesizes amino acids which form protein. 4. Regulates the uptake of other nutrients. 5. 重要化合物的基本成分——核酸和酶.
Phosphorus (P) 1. 刺激早期根系形成和生长——使植物有一个良好的开端，形成更大的根系生物量，使土壤区域更好地收集其他营养物质. Hastens maturity (conversion of starch to sugar). 3. Stimulates blooming and seed development. 4. 在糖转化为激素的能量转化和转化过程中必需的, protein and energy to grow new leaves and fruit. 5. Forms nucleic acids (DNA and RNA). 6. Vital for photosynthesis (greening for plants).
Potassium (K) 1. Aids in the development of stems and leaves. 2. Increases disease resistance and hardiness. 3. Strengthens cell wall. 4. Water intake by plant cells can be affected; plants with inadequate potassium may wilt with more than enough moisture. 5. Acts as a catalyst in Iron uptake. 6. Essential to the formation and translocation of protein, starches, sugar, and oil–improving the size and quality of fruit, grains and tubers.
