Each plant required essential elements at specific concentration on a specific stage of growth and this requirement known as Critical Level of Nutrient.
The Critical concentration of essential Nutrient in plant and in Soil are have differ values. In which Critical concentration of essential Nutrient in soil discussed below.
Determining the critical levels of essential nutrients in soil is crucial for proper plant growth and yield. The critical levels vary depending on the specific crop and soil type, but general guidelines are available for many nutrients.
### Macronutrients:
1. **Nitrogen (N)**: 20-50 ppm (as nitrate, NO₃⁻)
2. **Phosphorus (P)**: 15-30 ppm (Olsen P or Bray P1 for acidic soils)
3. **Potassium (K)**: 100-200 ppm
4. **Calcium (Ca)**: 1000-2000 ppm
5. **Magnesium (Mg)**: 50-200 ppm
6. **Sulfur (S)**: 10-20 ppm (as sulfate, SO₄²⁻)
### Micronutrients:
7. **Iron (Fe)**: 2.5-4.5 ppm
8. **Manganese (Mn)**: 1-5 ppm
9. **Copper (Cu)**: 0.2-0.5 ppm
10. **Zinc (Zn)**: 0.5-1.5 ppm
11. **Boron (B)**: 0.5-1 ppm
12. **Molybdenum (Mo)**: 0.01-0.1 ppm
13. **Chlorine (Cl)**: 1-10 ppm
14. **Nickel (Ni)**: 0.01-0.1 ppm
### Beneficial Elements :
15. **Cobalt (Co)**: 0.02-0.5 ppm
16. **Sodium (Na)**: 1-50 ppm (beneficial in small amounts for some plants but not essential)
17. **Silicon (Si)**: 10-100 ppm (beneficial in some plants)
These levels are general guidelines and can vary significantly based on the specific crop, soil type, and environmental conditions. For precise nutrient management, soil testing and consulting with local agricultural extension services are recommended.