AN INDICATOR OF PESTICIDE ENVIRONMENTAL-IMPACT BASED ON A FUZZY EXPERT-SYSTEM

Pesticide use options available to farmers differ strongly with respec t to the risks they pose to the environment. This paper proposes a fuz zy expert system to calculate an indicator ''Ipest'' which reflects an expert perception of the potential environmental impact of the applic ation of a pesticide in a field crop. We defined four modules, one ref lecting 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 modul es are pesticide properties, site-specific conditions and characterist ics of the pesticide application. For each input variable two function s describing membership to the fuzzy subsets Favourable (F) and Unfavo urable (U) have been defined. These functions are based on criteria dr awn from the literature or on the authors' expert judgement. The exper t system calculates the value of modules according to the degree of me mbership of the input variables to the fuzzy subsets F and U and accor ding to sets of decision rules. The four modules can be considered ind ividually 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 tuned 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 environm ental impact. Results of a sensitivity analysis and module and Ipest s cores for some pesticide application cases are presented. An agro-ecol ogical indicator IPEST, based on the expert system, is proposed as a t ool to assess the environmental impact of all pesticide applications r elated to a crop within a year. The practical implementation of the ex pert system and its validation are discussed. (C) 1998 Elsevier Scienc e Ltd. All rights reserved.