A year ago NATO and Afghan forces were seizing an average 60 tons of ammonium nitrate fertilizer a month. That was twice as much as 2011. This was part of an effort to deny the Taliban access to the most common explosive (using the fertilizer) for bombs. Currently 47 percent of roadside bombs are made with ammonium nitrate fertilizer, with about ten percent using old shells and bombs from the 1980s and the rest potassium chlorate. Over the last few years fertilizer bombs went from nearly 80 percent of all bombs to under fifty percent and falling. The terrorists have been substituting that loss with potassium chlorate (13 percent in 2011, 23 percent in 2012 and 45 percent this year). Potassium chlorate is more expensive than ammonium nitrate but not to the point where the terrorists cannot afford it. Potassium chlorate is a common industrial chemical used for all sorts of thing, including fireworks and matches.
In 2009, 60 percent of NATO dead in Afghanistan were from these bombs. It has declined ever since, in part because NATO and Pakistan has made it more difficult to get the raw materials for their bombs. For a long time the U.S. had a difficult time preventing the Taliban and drug gangs in Afghanistan from getting explosives. That was mainly because of the widespread use of ammonium nitrate fertilizer, which has become the favorite bomb building material after 2001. In response to these problems, four years ago, the Afghan government agreed to ban the use of ammonium nitrate and make available other (less effective) fertilizers. That program did not work as expected. The problem was that the terrorists only needed about 600 kg (1,320 pounds) of ammonium nitrate a day to keep their bombing campaign going. The existing smuggling network (from Pakistan) had no problem sneaking that much in. Paying locals to build and plant these bombs cost less than a million dollars a month. Pakistan was, for a long time uncooperative when it came to halting smuggling of explosives into Afghanistan. But then the Taliban began using fertilizer bombs more frequently inside Pakistan. That got the Pakistani government to crack down on their end.
With no such abundance of leftover munitions the Taliban had to fall back on a common local explosive (ammonium nitrate) early on. This is a powdered fertilizer that, when mixed with diesel or fuel oil, can be exploded with a detonator. While only about 40 percent of the power as the same weight of TNT, these fertilizer bombs are effective as roadside bombs. But they are bulkier and a slurry, usually mixed in a plastic jug or a barrel. Moreover, the fuel oil must be mixed thoroughly and in exactly the right proportion, otherwise the explosive effect is much less than expected.
While these bombs are even less effective in Afghanistan than in Iraq they are still the main cause of NATO casualties and thus get a lot of media attention. In Afghanistan the enemy started off with one big disadvantage, as they didn't have the expertise or the resources of the Iraqi bomb builders. In Iraq the bombs were built and placed by one of several dozen independent gangs, each containing smaller groups of people with different skills. The Taliban bomb gangs are much less skilled than those encountered in Iraq. At the same time, the equipment, techniques, and troops who neutralized the bomb campaign in Iraq have been moved to Afghanistan. This is a major reason the effectiveness of Taliban bomb attacks are declining so quickly.
The main reason the Taliban keep at it with the roadside bombs is that when the foreign troops leave after 2014, they will take with them the sensors and weapons that made it so difficult to use roadside bombs effectively. The Taliban expect these bombs to be much more successful against Afghan soldiers and police.