The farm-specific pollutant emission indicators were Nitrogen Surplus (kg) and the Environmental Impact Quotient (EIQ) for the pesticides used by the farm. Nitrogen surplus values were estimated using the Soil Surface Balance Method (OECD, 2001). This
straightforward method takes the nitrogen cycle as the reference and calculates the difference between the farm’s nitrogen inputs and outputs.
The pesticide toxicity index is based on the EIQ (Environmental Impact Quotient) method developed by Kovach et al. (1992), which provides an average estimate of the toxic effect of each active ingredient in pesticides on the health of farm workers, the health of consumers, and biodiversity. The farms’ EIQF (Environmental Impact Quotient of Farm) were calculated by aggregating the EIQ of the active ingredients contained in the pesticide used by the corresponding farm.
Data on nitrogen and pesticide use were gathered via interview with organic farmers. The pesticide and fertilizer usage levels of the conventional farms were estimated using the available FADN data and the cost of the representative fertilization and pesticide strategies for vineyards in Navarre recommended by the Navarre Agricultural Technical Management Agency. The descriptive statistics of the variables are given in Table 1