Utilization of a model to re-design integrated crop management for winter oilseed rape

Abstract: Concerns about the adverse impacts of pesticides on the environment and their inevitable negative side-effects on non-target organisms have been growing since the 1960’s. As a consequence, regulatory bodies take into account the environmental effects of pesticide applications, leading to increased restrictions in their use or to their revocation or banning (van der Werf, 1996). For winter oilseed rape (Brassica napus L.) in France, herbicides, fungicides and insecticides constitute the largest component of variable operating costs: representing 20% of the gross margin. On the other hand, in order to avoid disease occurrence, weed infestation and pest attack, diverse elementary control methods (genetic, cultural, mechanical, chemical) can be used in integrated pest management strategies (Dhaliwal et al., 2004, El Titi et al., 1993). Since each technical operation is likely to modify the sanitary status of a crop, it is therefore possible to design cropping systems to minimize crop loss induced by pest population with a limited use of chemical control. Because of the complexity of the considered systems due to interactions between cultural practices, crop status, soil, climate and pest populations, modelling is a key tool to propose innovative cropping systems less vulnerable to pests. Several experiments (1994-2004) have been used to analyze and simulate (i) the effects of agricultural practices on the pests and their interaction with the crop and (ii) the yield losses induced by pests. A bio-economic model, named OMEGA sys, has been developed in order to represent the effects of crop management either on crop yield, weed biomass and stem cancer attacks. The first aim of this model is to help in building environmental friendly crop management systems. The inputs of the model are climatic variables and the combination of each element of crop management, while the outputs are potential, attainable yield, number of pesticide treatments and gross margin. An algorithm of gross margin optimization is combined to the agronomic model in order to rank the diverse combinations of crop practices. This paper makes a short description of the OMEGA sys, gives some results of assessments and illustrates the new integrated crop management strategies than can be obtained with such methodology in two agronomical contexts and with two weed/disease pressures. Depending of the economic scenario, the first crop management strategy selected by the OMEGA sys are characterized by no or few pesticides utilization. The best crop management systems selected are different between the different agronomic context (soil, preceding crop and weed pressure).