Simulation of the behaviour of some pesticides for horticultural crops in soil using Italian scenarios

The PELMO model was used to carry out several simulations of the environmen tal behaviour for some pesticides currently used in tomato and lettuce in t hree horticultural Italian scenarios, i.e. Rovigo (RO), Perugia (PG) and Fo ggia (FG). For each pesticide, a comparison between its behaviour in the di fferent scenarios was performed and discussed in terms of carryover effects and groundwater pollution risks. Results show that degradation decay was t he main process of dissipation in all the scenarios, even though plant upta ke and runoff also played a role. While in FG scenario no leaching was obse rved three pesticides leached along the soil profile in RO and PG scenarios , i.e. metribuzin, metalaxyl and methomyl. Taking into account the legal li mit for pesticide concentration in drinking water, the use of metalaxyl in the PG scenario was the only situation that seemed to pose a certain risk o f groundwater pollution. However, simulations showed that wherever repeated applications of the above mentioned pesticides are carried out, some risks might exist which in practice may require an accurate monitoring of pestic ide fate. Concerning the risk of carryover of residues to following crops, some problems may exist for propyzamide, especially in RO and PG scenarios, where simulations showed negative effects on a wheat crop following the tr eated lettuce crop.