In Iowa, the powerful Farm Bureau and other ag industry groups oppose regulations that limit fertilizer application or require farmers to clean up the pollution coming off their land.

Instead, the state must coax farmers to use voluntary conservation tools. But many of those threaten crop output, reduce field acreage or require changes in farming practices.

One taxpayer-funded tool the state is promoting doesn't cause farmers any of those headaches: saturated buffers.

But research and records show Iowa's saturated buffers aren't as effective as promised. And even if the buffers met advertised standards, the state would need to increase installations exponentially to make even a marginal difference in water quality.