Cropdusters? In February?

Yesterday I heard the roar of a crop duster in the distance.  I couldn't figure out what it was, because there aren't any crops around here this time of year, and most of the fields have a foot or so of snow in them.

I found out later they were using crop dusters to spray coal ash over the frozen Platte river.  There's been so much snow and the weather has been so cold that when it starts to warm up, the ice in the river is going to jam up and cause massive flooding.  They're hoping the black coal ash will absorb the heat from the sun and cause the ice to break into smaller pieces, preventing an ice jam.