Land degradation has long been associated with declining crop productivity. Rubber, widely accepted to be an environment friendly crop, had not been studied in this respect. In this study a mathematical model embodying factors associated with output was estimated using a random sample of 170 mature rubber fields selected from 12 large estates in the Kalutara District. The explanatory variables are broadly grouped into three categories, viz variables associated with land degradation; current and lagged values of annual inputs; and completely exogenous variables both current and lagged. The model explains nearly 64 per cent of the variation in productivity. All the estimated coefficients show the expected signs. Most of the coefficients were statistically significant at conventional levels of significance. The analysis strongly suggests that observed variation in output is explained by land degradation, ie. soil loss and reduced soil fertility (organic carbon content). Rubber yield declines by 175 kg/ha/year for the loss of one cm of top soil whereas the output increases by 75 kg for every 0.1;increase in soil organic carbon content. The negative impacts of high elevation and steep slops on yield are also evident. Despite the drawback in using a single years cross sectional data and specifying a linear function, this study has succeeded in generating some key parameters which reflect certain key policy-environmental linkages.