Evaluating eco-efficiency and optimal levels of fertilizer use based on the social cost and social benefits in tea production.

The extensive use of synthetic fertilizers is increasing continuously to meet the growing demand of food worldwide. This excessive use of fertilizer not only pose a threat to the sustainability but also cause negative externalities in form of hidden social cost to the society The present study estimated social costs and benefits associated with excessive use of chemical fertilizers at tea farms and also evaluated eco-efficiency of tea growers in Rize Province of Turkey. Data envelopment analysis (DEA) was used in this study. Tea growers are 68% eco-efficient in the locality. They can reduce their average fertilizer use from 115.45 to 66.45 kg and labor from 9.88 to 8 days per decare. The overuse of fertilizers at tea farms emits 289.3 kg/hectare of greenhouse gases. Therefore, by applying the eco-efficient fertilizer target level, 1574.48 tons of gas emissions only in Rize Province and 23,997.57 tons in whole Turkey can be reduced. The cost of 1 kg gas emissions was calculated as 0.3316 TL. The optimal level of fertilizers (social costs = social benefits) was also similar to the target level. The fertilizer use efficiency analysis showed that the tea growers cannot only reduce their fertilizer quantity by 49.03 kg/decare without compromising the crop yield, but can also contribute to the healthy environment with a low level of greenhouse gas emissions. Tea growers should replace their older tea orchards with new ones in order to achieve social and eco-efficient levels as well as to maintain viable yield level.