Soil erosion and nutrient pollution of our water resources by agriculture are a growing concern.

Many people would argue that the Farm Bill should address these concerns so we get more out of all the money we pour into agricultural subsidies. But developing an effective strategy as part of a Farm Bill will not be easy.

Previous Farm Bills have encouraged the expansion of erosive crops. Attempts to mitigate the resulting environmental problems have relied on Best Management Practices for these crops and on land retirement. This approach has proven to be not enough.

For example, University of Minnesota soil scientist Gyles Randall says in 30 years he's never seen as much soil erosion in south central and southeastern Minnesota as he has in the last few years. Randall goes on to question whether the corn-soybean crop production system as we know it today is sustainable.

Randall says substantial changes in federal farm policy, cropping systems and use of crops produced on farms will need to occur to sustain a healthy environment and rural community.

We must move away from intensive corn-soybean rotations to more diversified cropping systems if we're serious about reducing nitrate and phosphorus pollution of the Minnesota River by 40%. This was a publicly stated goal several years ago. More than conservation tillage, grass waterways and careful application of fertilizer nutrients are needed.

Including alfalfa in the cropping system would reduce nitrate pollution. We know nitrate discharge from tile drains is much lower when alfalfa is grown, compared to corn and soybeans. In addition, alfalfa provides a year-round soil cover that prevents soil erosion. The downside is that alfalfa is not as profitable as corn or soybeans and is not supported in the present government program.

Phosphorus pollution could be significantly reduced with changes in farming practices and amounts of fertilizer or manure applied. However, changing farming practices may mean no row crops close to water bodies. In addition, it may require new methods to encourage farmers to prevent soil and phosphorus loss. One such method might be tradable phosphorus pollution permits.

It is clear that we need more than environmental tinkering with the Farm Bill if we want to significantly reduce nutrient pollution from agriculture. Top-down approaches in past Farm Bills have had only limited success in reducing pollution. What we need are changes that give farmers incentives to switch to more sustainable cropping systems.