Earlier, I posted a quote from the Environmental Defense Fund's Joe Rudek that stated that a carbon tax would have probably no effect on agriculture. Technically that should say no direct effect on agriculture. There is a possible indirect impact. Last week, the federal Biomass Research and Development Board released a "Biofuel Feedstocks Report" that stated farms could be impacted by a carbon tax due to a rise in fertilizer production costs.
The board found that a carbon tax or high costs for inputs like fossil fuel-derived fertilizers could offset the pressure to plant more acres for biofuels, perhaps even pushing land use below the 2007 baseline level.
Also, in the earlier post, many references were made to taxing cows' asses for the methane they produce, assuming most comes from their rear ends. Most methane emissions actually come from burps -- eructation -- not from the other way around.