The marketing year for soybeans is September 1 through August 31. Even though there are general seasonal basis trends, there can be important differences between years. The dramatic increase in basis values beginning in July 2013 was a result of very tight U.S. soybean supplies due to drought conditions in 2012. In early July, elevators used the August futures market contract as the reference point for pricing 2012 production. By August, elevators switched to the September futures contract as the reference price for 2013 production.

The 2013 soybean crop was much larger than the 2012 crop, and prices for 2013 production, as reflected in the September contract, were much lower than prices for 2012 production, as reflected in the August contract. Thus, the basis levels went from being extremely strong to near normal in a few days. Basis values tend to be weakest, with the largest negative values, during harvest. The cash market is signaling farmers that too much grain is flowing, and there is a disincentive to deliver and sell more grain.

Basis values tend to strengthen, or become less negative, in January, February and March. Grain deliveries are slower during the winter months, and the cash market provides an additional incentive for farmers to deliver grain during the winter. Basis values then tend to weaken as the market gets more information about the size of the new crop and as farmers sell their remaining old crop inventories to prepare for the upcoming harvest.