Ecotoxicological risk assessment of agriculture intensification in Argentinean cropping lands using a fuzzy-logic based model

Abstract

Current agricultural models have an increasing dependence on non-renewable resources that have significant implications for the ecosystem health. Pesticides are considered one main impact force that affects both the structure and functions of agroecosystems. In this work we presented results from the application of an environmental pesticide risk assessment of a large database of cropping systems in the Inland Pampa (Argentina) where, since 1990, the traditional mixed grazing–cropping systems were being replaced by permanent agriculture and the intensification of pesticide use has increased significantly. However, there is no clear awareness of the ecotoxicological risk associated with these land use changes. The ecotoxicological risk on both insects and mammals were assessed using a fuzzy-logic based model that links, as input variables, the amount the pesticide dose and the lethal dose (LD50) of each active ingredient use in a single crop field. Thresholds and membership functions were developed by means of expert opinion. A database, containing 29042 records of pesticide use in maize, soybean, sunflower and wheat from 1992 to 2005 were analyzed. Results showed that harvested yield increased significantly in all crops during the period studied (P<0.005). However, these higher yields were associated with higher risks over both insect and mammals as in almost all crops analyzed the fuzzy-logic ecotoxicological indicators showed negative and significant time trend in the period studied (P<0.005, Spearman rank correlation (SRC)). Summer soybean (i.e in the wheat-soybean rotation) did not show any significant tendency regarding changes in potential ecotoxicological risk during 1992-2005 interval. However, soybean (either as summer or spring crop) showed the highest ecotoxicological risk value in each one of the years analyzed (Kruskal-Wallis test, p < 0.05). Regarding the average number of pesticides applied, all crops showed a significant increment from 1992 to 2000 and a subsequent reduction from 2000 to 2005 (SRC, P < 0.05) and these reductions were higher in soybean, from 6.1 to 3.5 application/year in relation to maize, soybean and sunflower. These preliminary results indicated that higher yield in all the crops analyzed were associated to higher ecotoxicological risk of the pesticides used. However, further work has to be conducted to improve the fuzzy-logic ecotoxicological model by including variables such human toxicological risk or other chemical pesticide characteristics (i.e. soil persistence, solubility).