Chemical rotation studies field testing

Pesticides used on crops grown on the test site in previous seasons may also have an impact on the outcome of a field residue trial. Carryover of prior pesticide applications could contaminate samples in a new trial, complicate the growth of the crop in a trial, or cause interference with procedures in the analytical laboratory. For this reason, an accurate history of what has transpired at the potential test site must be obtained before the trial is actually installed. The protocol should identify any chemicals of concern. If questions arise when the history is obtained, they should be reviewed with the Study Director prior to proceeding with the test site. In most annual crop trials, this will not be a significant issue owing to crop rotations in the normal production practices, because the use of short residual pesticides and different chemical classes is often required for each respective crop in the rotation. However, in many perennial crops (tree, vines, alfalfa, etc.) and monoculture row crops (cotton, sugarcane, etc.), the crop pesticide history will play a significant role in trial site selection. 

This study comprises a theoretical investigation of all possible stable conformers of two monomers and a dimer containing alkyl-bound ether fragments simulated with two quantum chemical methods. Basic structural parameters, characteristic vibrational frequencies and atomic electron density distribution are evaluated. Rotation barriers about the ether bond are estimated. The mean values of these quantities averaged over the entire conformer ensemble are supplemented to the parameters of the molecular mechanics force field AMBER and tested by several molecular dynamics simulations of one of the model systems - diethyl ether. 

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