There's no better example of the environmental challenges posed by agriculture than the 6,600 square mile "dead zone" in the Gulf of Mexico.

The nutrients in fertilizer and manure than help crops grow also fuel the growth of algae, which consume oxygen as they die and decompose. Eventually, oxygen levels fall too low to support marine life, killing some organisms and driving away others.

In 2001, a White House task force pledged to reduce the dead zone by using fertilizers with greater care and restoring wetlands to intercept and filter polluted runoff. The 2002 Farm Bill doubled funding for farmland stewardship, but more than $4 billion were cut to pay for disaster assistance and two out of three farmers offering to share the cost of clean water continue to be turned away.

Now, the Saint Louis Post Dispatch warns, surging corn production could make the dead zone even bigger.

But this week, a group of scientists will release a study that shows that the dead zone could largely be eliminated through a combination of actions: more precise fertilizer applications, wetland and grassland restoration, expanding pasture-based livestock operations and growing energy crops like switchgrass. The study shows that farmers could reduce the amount of nitrogen — a component of fertilizer — reaching the Gulf by 40 percent with no impact on their bottomline.

Bringing the dead zone back to life will require one thing more — that Congress dramatically expand farmland stewardship programs when legislators renew farm policies in the 2007 Farm Bill, according to the study.

More than 200 members of the House of Representatives have co-sponsored bills, including the Healthy Farms bill and the Eat Healthy bill, to double USDA conservation spending.

But, so far, House leaders have placed outdated farm subsidies ahead of farmland stewardship. As the Des Moines Register said this month, Congress needs to make conservation "the top farm bill priority" if we hope to clean up our rivers, lakes and bays and meet our other big environment challenges.