If you've ever driven through the southern end of California's Central Valley in September, you're familiar with the grids of lint-strewn cotton fields that blur by for nearly 2 1/2 hours. You might even have pondered the wisdom of planting such a thirsty crop as cotton on a million acres — an area larger than Yosemite National Park — in a state facing a water crisis. Then again, you might ask a similar question about the half a million acres of rice, a grain adapted to the monsoons of Asia, on the valley's northern end.

Cheap irrigation water is part of the equation, but there is another common denominator. It's a massive federal legislation package passed every five years known as the farm bill, which House and Senate members are scrambling to reauthorize by an April 18 deadline. Over the past decade, the farm bill has allowed the U.S. Department of Agriculture to shower tens of billions of dollars in subsidies on the nation's cotton and rice farmers (along with corn, soybean, wheat, sugar and milk producers). These subsidies flow whether growers need them or not. They flow even as they damage the environment and our nutritional well-being. They flow, all the while enabling the biggest farms to consolidate into mega-farms.

It wasn't always this way. The farm bill emerged during the Dust Bowl and Great Depression as a temporary financial safety net for family farmers. It included programs to promote soil conservation and distribute food surpluses to the needy. But the farm bill has grown into a high-stakes game of political horse-trading that has changed how we farm and what we eat. Today, more than a third of the budget goes to an elite group of commodity farms that grow grains and oilseed crops, mainly for feeding livestock and making processed foods (and fuels).

When current farm bill negotiations started in 2006, a proverbial food fight erupted. An array of nonprofit organizations, including Oxfam, Bread for the World and the Sustainable Agriculture Coalition, pushed for a bill that would emphasize farming livelihoods, more effective environmental protection and better nutrition. Prices on nearly all commodities, except cotton, have been soaring. Average 2008 farm household income is anticipated to reach $90,000 — nearly 20 percent above the national average. Meantime, commodity farmers were set to receive $13 billion in direct and indirect payments, disaster bailouts, crop insurance and (some worthy) conservation incentives in 2008 alone. Surely, reformers argued, this was the right time to stop throwing money at giant farming operations already making hay in current markets.

A few worthy new programs were added: funds for organic farming research and to help pay organic certification fees; an expansion of local farmers markets; assistance for beginning farmers; and support for "specialty crop" producers, who for decades have been locked out of the subsidy game. (Specialty crops is farm-bill-speak for crops that are actually edible, such as fruits, nuts and vegetables, which many California farmers supply to the nation.)

But by and large, the farm bill song remains the same: Commodity agribusiness gets the lion's share; reformers get table scraps. Absent a more vocal public outcry, the agribusiness lobby, which spent $80 million in 2007, holds the winning hand.

What can we citizens expect if the proposed $300 billion farm bill is signed into law? Federally subsidized feed — corn, soybeans and cottonseed — for animal factory farms that spread disease, greenhouse gases and dangerous working conditions wherever they set up shop. The continuation of America's obesity campaign, which ensures the cheapest and most widely available foods are made up of such high-calorie ingredients as high-fructose corn syrup, refined flours, saturated fats and unhealthy meat and dairy products. And more federally backed exports of California's water — in the form of cotton and rice, mostly sold overseas.

But here's the one that's really hard to stomach. More than $4 billion in permanent disaster assistance to growers in the Northern Plains. The brainchild of Montana Democrat and Senate Finance Committee Chairman Max Baucus, this is essentially a trust fund to guarantee income to farmers plowing up prairies and grasslands — lands prone to drought and erosion — to plant corn and wheat. Many observers fear a second Dust Bowl.

No final bill has been passed, and President Bush, who signed the extravagant 2002 farm bill, has threatened a veto if considerable reforms aren't made to commodity programs. There is still time to let everyone in Congress know that they should vote on the farm bill as if the nation's very health, future and security is at stake. Because it is. And we deserve better.

Imhoff is the author of "Food Fight: The Citizen's Guide to a Food and Farm Bill." He wrote this commentary for the Los Angeles Times.