The Environmental Protection Commission Tuesday approved a rule that will limit the amount of liquid manure farmers can spread on their soybean fields. Gene Tinker is the animal feeding operations coordinator with the Iowa Department of Natural Resources.

Tinker says the rule would limit the application of manure to land planted or proposed for planting soybeans to 100 pounds of actual nitrogen applied to the land.

Tinker says, if approved, the limit would last for five years, and after the five years the rule would ban all nitrogen from manure on soybean fields unless there is scientific evidence that would change the ban. The E-P-C has been discussing the issue for the last six months, and Tinker says the idea is to prevent overuse of manure as a fertilizer.

Tinker says, “The bottom line is to reduce the amount of nitrogen going into waterways through tile lines and such. Since soybeans will generate their own nitrogen, and there is evidence that soybeans, as well as corn, don’t utilize all the nitrogen that is applied, the theory is that if we apply less nitrogen to these fields, since soybeans will produce their own and generate a good yield without the additional nitrogen — that there’s no reason to apply it since some of it will get into our waterways.”

Tinker says the rule would leave some openings in the case of bad weather. Tinker says if farmers apply manure in the fall in anticipation of planting corn, and the weather prevents them from planting corn, the rules allow them to plant soybeans in the field after June 1st. Tinker says the rules still need to get public comment and legislative approval.

Tinker says it will probably be into March or April until they can get comments and the proper reviews before the rules would go into effect. Tinker says the D-N-R isn’t sure how much the new rules might cut back the amount of nitrogen that gets into waterways. Tinker says they don’t know because they haven’t been looking for the nitrogen overflow because there were no restrictions, because farmers were allowed to apply manure based on their management plans.

Tinker says the D-N-R has not been testing the water in tiles for excess nitrogen. Tinker says they do have some scientific evidence from Iowa State University and the University of Minnesota to indicate there’s excess nitrogen runoff from manure applied to bean fields.