YIELD DAMAGE FUNCTIONS FOR TEA SECTOR IN SRI LANKA AND INDIA: AN EMPIRICAL ESTIMATION

A Yield damage function helps to illustrate by relating yield damage and some independent parameters of soil such as top soil depth and organic matter content. But erosion damage function furnishes the monitory values and losses in relation to soil erosion. An erosion damage function refers to the private economic benefits forgone when an erosive practice is adopted instead of a conservation practice. Even though, erosion damage function is imperative to evaluate the on site effects of soil erosion to the plantations economy, it is important to estimate yield damage function before the erosion damage function is estimated. Yield damage function facilitates to identify severity of yield reduction in tea crops on different topsoil depths. The study was focussed on three tea growing district, Passara and Watawala sub district of Sri Lanka and the Nilgiris district of India. For this study, 208 tea fields from Passara, 52 tea fields from Watawala/Ginigathena and 96 tea fields from the Nilgiris districts were selected. The results of the study show that the Passara region is responsible for higher yield damage due to top soil reduction and poor ecological condition. If the Nilgiris is in a condition to manage the issue, Passara tea region of Sri Lanka is required immediate actions to control the problem for sustainability of tea industry of the region.