Potash has been in retreat since 2012 and recently has bottomed at its lowest level since DTN began accumulating retail prices in 2008. (DTN chart)

OMAHA (DTN) -- As has been the trend in recent weeks, retail fertilizer prices continued to decline the third week of September 2016, according to retailers tracked by DTN. All eight of the major fertilizers are lower compared to last month.

Leading the way lower again this week is 10-34-0. The starter fertilizer is 6% lower compared to a month earlier and averaged $470 per ton.

The remaining fertilizers were all lower compared to a month ago, but the move was slight. UAN28 averaged $225/ton, UAN32 averaged $271/ton, DAP averaged $443/ton, MAP $453/ton, potash $319/ton, urea $323/ton and anhydrous $494/ton.

On a price per pound of nitrogen basis, the average urea price was at $0.35/lb.N, anhydrous $0.30/lb.N, UAN28 $0.40/lb.N and UAN32 $0.42/lb.N.

Lower fertilizer prices have been the main contributor to farm budget savings in the past year, farm economists note. Some nutrients have actually retreated to levels not seen since DTN began accumulating retail prices in November 2008.

Right now, two fertilizers remain at their lowest level in the last eight years. One might be fairly easy to guess if you have paid attention to fertilizer trends at all. That would be potash. The $319-per-ton average price is DTN's all-time low price. The potash chart is interesting to examine as it has been on a decline since May 2012.

You might think this adjustment in potash prices was because of the break-up of the so called "potash cartel," but that didn't happen until August 2013. Prices were already on the decline, and the demise of the cartel has only pushed potash prices lower over the last three years.