Mineral fertilizers

A plant takes water and mineral substances as ions from the soil; after the harvest they run low, so mineral fertilizers are added. The macronutrients needed in large amounts are C, H, O, N, P, S, K, Ca, Mg; the micronutrients needed in small amounts are Fe, Mn, B, Cu, Zn, Mo, Co. The most important nutrient elements are N, P and K. With too little nitrogen the plant grows slowly and its leaves are pale green or yellowish; phosphorus is needed for roots, flowers and seeds; potassium speeds up photosynthesis and accumulation of carbohydrates and strengthens the stem. The nutrient content of a fertilizer is expressed as the mass fraction of N for nitrogen, P₂O₅ for phosphorus and K₂O for potassium. A fertilizer with one nutrient element is simple (NH₄NO₃, KCl), one with two or three is complex (KNO₃, NH₄H₂PO₄). Fertilizer must be applied in the right amount: an excess builds up nitrates in produce, pollutes groundwater and open water, and makes algae multiply in water bodies. Mineral fertilizers are chemicals: keep them away from small children and from flammable materials, use gloves, never mix them and apply them only under an adult’s guidance.