gen-define-soil-nutrient-cycles-npk-and-give-one-short-worked-ex-5fda

Define soil nutrient cycles (NPK) and give one short worked example.

# Soil Nutrient Cycles (NPK) ## Definition Soil nutrient cycles are biogeochemical processes through which essential elements move between organic and inorganic forms in the soil-plant-atmosphere system. The three primary macronutrients are: - **N (Nitrogen)**: Critical for proteins, enzymes, and chlorophyll - **P (Phosphorus)**: Essential for ATP, DNA, and root development - **K (Potassium)**: Regulates water balance and enzyme activation These nutrients cycle through processes including: - **Mineralization**: decomposition releasing nutrients - **Immobilization**: microbes incorporating nutrients - **Plant uptake**: roots absorbing nutrients - **Leaching**: water carrying nutrients deeper - **Fixation**: conversion to plant-available forms ## Worked Example: Nitrogen Cycle in a Crop Field **Scenario**: A farmer grows corn that removes 180 kg N/ha from soil. **Nitrogen inputs:** - Atmospheric fixation: 5 kg N/ha - Applied fertilizer: 150 kg N/ha - Mineralization from organic matter: 40 kg N/ha - **Total inputs = 195 kg N/ha** **Nitrogen outputs:** - Crop removal: 180 kg N/ha - Leaching losses: 10 kg N/ha - Denitrification (gas loss): 5 kg N/ha - **Total outputs = 195 kg N/ha** **Result**: The system is balanced (inputs = outputs), maintaining soil fertility without N depletion or excess accumulation.