Assessing the impact of irrigation treatments on thiram residual trends: correspondence with numerical modelling and field-scale experiments.

The present study was undertaken to study the trends of transport of thiram, a dithiocarbamate pesticide, at different time and depth in the fields under real field conditions for wheat crop. Numerical simulations were carried out by solving the coupled soil-water content movement and mass transport equations using HYDRUS- 1D. The supplementary data used for paramaterization of HYDRUS-1D comprise of irrigation treatments, climatic conditions, and soil characteristics. Results focus on the effects and influence of irrigation treatments on pesticide persistence and mobility. Modelling results were in good agreement with the experimentally determined thiram concentrations. Application of the model to measured field data of thiram movement indicates that the modelling approach can provide reliable and useful estimates of the mass flux of water and non-volatile pesticide in vadose zone. For policy-makers and planners, some regulation strategies are suggested for controlling inappropriate pesticide application under deficit irrigation or rain-fed conditions.