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The Minnesota Legislature passed a new law this year requiring that residents use phosphorus-free fertilizer in the seven-county metro area (unless testing reveals low levels of phosphorus in their lawn) and reducing the amount of fertilizer in the outstate areas to three percent.

Local governments could lower the amount of phosphorus sold to homeowners, but the board of supervisors just recommended the use of phosphorus-free fertilizer.

Phosphorus from lawn fertilizer can wash into the storm sewers or directly into a river, lake, or other surface water. According to the Minnesota Pollution Control Agency (MPCA), just as it helps grass to grow, phosphorus in fertilizer feeds algae. When algae die and decompose, the process depletes dissolved oxygen in the water, which can cause fish and other aquatic life to suffer and die.

The amount of phosphorus in fertilizer is indicated by the middle analysis number on the bag. For instance, a fertilizer with the analysis number of 10-0-10 is phosphorus-free.

The Koronis Lake Association approved helping with the phosphorus-free fertilizer campaign at its annual meeting in July, when members voted to conduct an education effort, including posting signs at local retailers where fertilizers are sold.

Fertilizers for farms and golf courses are exempt from the new phosphorus-free requirements.