In relation to the sanitary quality of the harvest products, the Quasagro project aimed at validatingelements of global management of multicontaminant risks (mycotoxins, metallic trace elements andpesticide residues) ...
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In relation to the sanitary quality of the harvest products, the Quasagro project aimed at validatingelements of global management of multicontaminant risks (mycotoxins, metallic trace elements andpesticide residues) associated with environmental factors and agronomic practices in field crops (softwheat, durum wheat and sunflower) by multifactorial analysis: soil and climate conditions effects, cropresidues, inputs and addition of organic matter. It relied on the national Quasaprove plot network,reinforced by existing field experiment.By an approach without a priori, statistical models were tested on soft wheat, based on soil or climaticparameters. No model proved to be sufficiently predictive. We also examined whether certain practicesled to differences in concentration in plants. It was found that there was no difference between plowedand unplowed plots, depending on the type of fertilization, the preceding crop or the use of a CIPAN.There was no difference between plots in organic agriculture or in conventional agriculture. Whateverthe crop, the balance was determined by the type of fertilization. In the case of nitrogen-only fertilization(ammonitrate), the balance was always negative. In the case of organic fertilization in organic farming,the balance was always positive and the soil accumulated trace elements. In the case of conventionalagriculture with NPK fertilization, the balance was positive for arsenic, cadmium and lead, and negativefor copper and zinc. The export of straws, which generated a relatively small export flow, did not changethese conclusions.On the studied plots, the cumulative concentration levels observed ranged from sub-ng/g to 100 ng/g(dw) in soils. The maximum cumulated concentrations in organic farming were close to 10 ng/g. Bycomparison of conventional / biological technical itinerary, herbicides were markedly present inconventional and almost absent in biological; fungicides were present in biological at concentrationsabove the limits of quantification and the levels of fungicides were relatively similar in biological and inconventional called reasoned. The significant presence of persistent pesticides (epoxiconazole, whichlast treatment were several years ago) has also been highlighted.The future of pesticides in the environment is conditioned by their behavior in soils. The interactionbetween various processes governing their future (retention, degradation, transfer) will determine,among others, their persistence (or remanence). In particular, pesticide degradation processes help to reduce this persistence. The potential of microbial biodegradation depends on the molecules (intrinsictoxicity, soil adsorption capacity), soil and climate factors (type of clays, organic matter, temperature andhumidity), microbial factors such as global biomass and the presence of microorganisms adapted tocertain molecules (isoproturon, 2,4-D) and historical treatments (frequency of treatment).In general, low input systems seem to favor soil microbial activity in comparison conventional systems.
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