The application of manure phosphorus at rates above crop uptake has resulted in water pollution for some regions. In response, new manure management standards will require some farms to match manure phosphorus application rates with crop uptake. For some regions, this will lead to more crop acres and a shift toward crops with greater nutrient uptake, both of which will increase nitrogen runoff. The greater nitrogen runoff could offset the lower phosphorus runoff to result in greater water pollution. This demonstrates the law of unintended consequences, which results when policy does not consider how economic agents respond to incentives.