– BNSF Railway Co. hopes to deliver 52 trainloads of critically needed fertilizer across the Upper Midwest in the next six weeks so farmers will be able to plant crops.

Supplies of fertilizer are running dangerously low due to rail congestion caused by bad weather and increasing numbers of trains carrying crude oil out of North Dakota. BNSF laid out its plan in a Wednesday filing with the U.S. Surface Transportation Board.

The plan envisions using faster loading/unloading methods usually used for grain shuttles at fertilizer facilities. It also allows locomotives to stay attached to fertilizer trains instead of the customary ­practice of detaching them during loading and unloading. This should speed up ­turnaround times, the railroad said.

BNSF will add 110 "jumbo hopper cars" to its fleet of fertilizer carriers that will increase the amounts carried on trains that range from 65 to 85 cars each.

Finally, the railroad promised to have crews in position to move trains immediately after they are loaded and unloaded and to give customers earlier notice so they can have workers in position to load or unload products as soon as trains arrive.

BNSF said the enhanced deliveries began Saturday, two days after the railroad and its frustrated agricultural customers testified at a Transportation Board hearing in ­Washington.

In one complaint, the leader of a South Dakota cooperative complained that his farmers' supply of fertilizer for spring planting had been cut by a third because shippers could not get it there.

U.S. Sens. Al Franken of Minnesota and Heidi Heitkamp of North Dakota, both Democrats, pushed the Transportation Board and the railroad for answers on how the fertilizer shortage would be dealt with.

"We are already seeing positive progress against our planned goal," the railroad said in its filing. "We believe that will be reflected in the initial report that we will provide at a later date in response to the Board's request for additional information on fertilizer deliveries."