1. What is Residual Sodium Carbonate?

Residual Sodium Carbonate (RSC) is a water quality parameter that indicates the excess of carbonate and bicarbonate over calcium and magnesium in irrigation water. It helps assess the potential for soil sodicity and alkalinity hazards.

2. How Does the Calculator Work?

The calculator uses the RSC equation:

Where:

• \( CO_3 \) — Carbonate concentration (meq/L)
• \( HCO_3 \) — Bicarbonate concentration (meq/L)
• \( Ca \) — Calcium concentration (meq/L)
• \( Mg \) — Magnesium concentration (meq/L)

Explanation: The equation calculates the net balance between alkaline carbonates/bicarbonates and alkaline earth metals (calcium and magnesium) in water.

3. Importance of RSC Calculation

Details: RSC values help determine irrigation water quality. High RSC values (>2.5 meq/L) indicate potential for soil sodicity, which can lead to reduced soil permeability and crop yield.

4. Using the Calculator

Tips: Enter all concentrations in meq/L (milliequivalents per liter). Ensure all values are non-negative. The calculator will compute the RSC value.

5. Frequently Asked Questions (FAQ)

Q1: What do different RSC values indicate?
A: RSC < 1.25 meq/L: safe; 1.25-2.5 meq/L: marginal; >2.5 meq/L: unsuitable for irrigation without treatment.

Q2: How is RSC related to SAR?
A: Both assess irrigation water quality, but RSC focuses on carbonate balance while SAR (Sodium Adsorption Ratio) evaluates sodium hazard relative to calcium and magnesium.

Q3: Can RSC be negative?
A: Yes, negative RSC values indicate excess calcium and magnesium over carbonates, which is generally favorable for irrigation.

Q4: How to convert mg/L to meq/L?
A: Divide concentration in mg/L by the equivalent weight: CO3 (30), HCO3 (61), Ca (20), Mg (12.15).

Q5: What are the limitations of RSC?
A: RSC doesn't account for total salt content or specific ion toxicity. Should be used alongside other water quality parameters.