Distribution of Imidacloprid Residues in two Sandy Soils of Portneuf (Quebec) Under Potatoes (Solanum tuberosum) Culture

Aims: The goal of this work was to confirm the results of leaching and dissipation of the imidacloprid obtained with intact soil columns and draining lysimeters.

Methodology: A study on the distribution of imidacloprid (insecticide) residual deposit was carried out on two potatoes (Solanum tuberosum) farms of Portneuf (Quebec). Two farms (PNF47 and PNF51) were selected. The soil was sampled once before and four to five times after imidacloprid application. Imidacloprid residues analysis was performed using HPLC.

Results: The results obtained show that the average concentration of imidacloprid after application is lower or equal to the theoretically expected values. The imidacloprid was recovered in the soil 2 to 6 days after foliar application at rates varying between 23.2 to 23.6%. The heterogeneity of active ingredient distribution on the soil at application, differential dissipation of this one and foliar interception explain these results. The coefficients of variation of the concentrations observed in the layer 0 to 5cm, 2 to 6 days after application vary from 76 to 96%. The soil contamination after harvest is 2 to 6% of the amount of imidacloprid applied. The vertical distribution profiles of the residual concentrations of imidacloprid after application show that, these vertical profiles of distribution vary from a sampling point to another. The residual concentrations in the deep layers of the soil are independent of the concentrations in the surface layers (absence of correlation).

Conclusion: The risk of pesticide leaching below the root zone of the soils studied is small in the context of crop rotation. But there is no zero risk. The data obtained can be used in the development, calibration and validation of the various models of digital simulation.