An indicator of pesticide environmental impact based on a fuzzy expert system.

Pesticide use options available to farmers differ strongly with respect to the risks they pose to the environment. This paper proposes a fuzzy expert system to calculate an indicator "Ipest" which reflects an expert perception of the potential environmental impact of the application of a pesticide in a field crop. We defined four modules, one reflecting the presence (rate of application) of the pesticide, the other three reflecting the risk for three major environmental compartments (groundwater, surface water, air). The input variables for these modules are pesticide properties, site-specific conditions and characteristics of the pesticide application. For each input variable two functions describing membership to the fuzzy subsets Favourable (F) and Unfavourable (U) have been defined. These functions are based on criteria drawn from the literature or on the authors' expert judgment. The expert system calculates the value of modules according to the degree of membership of the input variables to the fuzzy subsets F and U and according to sets of decision rules. The four modules can be considered individually or can be aggregated (again according to membership to fuzzy subsets F and U and a set of decision rules) into the indicator Ipest. The system is flexible and can be turned to expert perception, it can be used as a decision aid tool to rank or choose between alternative pesticide application options with respect to their potential environmental impact. Results of a sensitivity analysis and module and Ipest scores for some pesticide application cases are presented. An agro-ecological indicator IPEST, based on the expert system, is proposed as a tool to assess the environmental impact of all pesticide applications related to a crop within a year. The practical implementation of the expert system and its validation are discussed.