Microbial biomass carbon, though a small fraction of soil organic carbon (1-3%), has a rapid turnover rate and is a labile reservoir of nutrients. Changes in Microbial Biomass Carbon (MBC) and soil properties were studied after 14 years of Sodic Water (SW) irrigation with different levels of gypsum and application of Farm Yard Manure (FYM), Green Manure (GM) and Wheat Straw (WS) to a sandy loam soil under rice wheat system. Pools of carbon extractable by 0.5 M Potassium Sulphate (PSC) and 1 M Potassium Nitrate (PNC) were quantified to study relationship with Microbial Biomass Carbon (MBC). Long-term irrigation with SW significantly deteriorated the soil properties such as pH, Electrical Conductivity of saturation extract (ECe), Exchangeable Sodium Percentage (ESP), Sodium Sdsorption Ratio of saturation extract (SARe), bulk density and final infiltration rate of soil. Application of gypsum and organic amendments resulted in improvement of all these soil properties. Deterioration in soil properties under SW irrigation caused significant decrease in MBC. The MBC decreased to 44.6 mg kg-1 soil under SW from 120.0 mg kg-1 soil under CW in 0-7.5 cm soil layer and to 17.3 mg kg-1 soil from 47.0 mg kg-1 soil in 7.5-15 cm soil layer. Application of gypsum significantly increased MBC at all doses. Organic amendments significantly increased the mean MBC over the unamended treatment up to 15 cm soil depth and followed the order: GM > FYM > WS. GM application resulted in four-fold increase in MBC. Changes in soil properties - pH, ECe, ESP and SARe could explain 75 to 85% variation in MBC in different treatments. Sodic water irrigation significantly decreased mean PSC from 87.5 (CW) to 46.9 mg kg-1 soil and mean PNC from 65.6 under CW to 32.8 mg kg-1 soil in the surface 0-7.5 cm soil layer. The trend was similar in 7.5-15 cm soil layer. Application of gypsum increased PSC and PNC. Organic amendments significantly increased the mean PSC and PNC values and followed the order: FYM > WS > GM. There was a three fold increase in extractable C pools due to FYM application. Microbial biomass C was significantly correlated with PSC and PNC; higher coefficients of correlation were observed for 0-7.5 cm soil layer than 7.5-15 cm soil layer.