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The deflation of farm prices and the collapse of the land boom after World War I bit many of the farmers very hard . Scientists theorize that could be due to power-plant emissions that help form cooling clouds or the conversion of farm fields to forests . One-dimensional thinking thus leads to a monoculture of farm animals bred and maintained through extemal imported inputs for an export oriented economy . Because of the rural nature of Northern Louisiana and the abundance of horses and livestock , iodine crystals , commonly used in the handling of farm animals and as precursor chemical used in the ephedrine process of methamphetamine manufacturing , are widely available and accessible . An off-road vehicle may qualify for a sales tax exemption if it is used in the production of farm and ranch products .