It's unlikely that the end of prohibition would have a large impact on agriculture; growing weed usually requires an indoor or greenhouse environment to prevent

It's unlikely that the end of prohibition would have a large impact on agriculture; growing weed usually requires an indoor or greenhouse environment to prevent pollination, it doesn't really lend itself to large-scale production, and the amount that people smoke is minuscule compared to tobacco/cigarettes. Of course, tobacco companies could roll out some industrial processing machines and drive the price of production down near to zero, but as long as the government uses taxes to keep the price high, people will demand the kind of quality that requires more of a greenhouse type of a solution.