When the agricultural commissioner issues Ventura County's annual crop report each July, it's like getting the results of an aging relative's medical tests.

Hidden in the dry collection of numbers — harvested acreage, gross revenues and per-unit values for each commodity grown in the county — are clues to the status of the industry's health. And that ought to concern everyone living here, not just the owners and operators of the county's 2,300 farms and ranches.

That's because farming defines and shapes the local landscape to a degree that is unprecedented in coastal Southern California: For every acre of pavement and rooftop in Ventura County, there's an acre of irrigated farmland. The primary factor keeping that land green and productive, rather than paved or abandoned to dust devils and tumbleweeds, is the continuing ability of farmers to make money cultivating it. And that means the industry's economic health has a direct bearing on the local quality of life, which benefits considerably from the verdant fields and orchards that prevent local cities from running together in a featureless sprawl.

The industry's health appears to be reasonably sound for a patient nearing 150 years of age. The latest crop report estimates 2006 farm revenues at $1.5 billion, a record high.

But it is easy to draw misleading conclusions by examining each year's crop report in isolation, or by taking the numbers at face value. By analyzing data from several years, it's possible to identify trends that tell a more useful story about where the industry might be headed. And when you do that, the news is less hopeful than the record value tallied by the 2006 report might suggest.

Digging through the archive of county crop reports also is an interesting historical exercise, for they have changed dramatically over time to reflect the changing nature of Ventura County agriculture. For more than a century, the industry's signature trait has been adaptability in the face of changing economic and market conditions, and the reports catalog the successive rise and fall of dominant crops in the county's commodity mix: grain, beets, beans, citrus, berries, nursery stock.

What those reports reveal in recent years is a nearly stagnant industry operating on a shrinking land base, its overall economic productivity maintained only by shifts to higher-value crops.

Adjusted for inflation, the overall crop value has hovered right around $1 billion a year over the past 30 years. There have been occasional upward and downward blips from year to year, and last year's figure was indeed the highest ever. But at $1.29 billion, it was only marginally higher than the 2004 total of $1.27 billion (in 2000 dollars), and both represent departures from the long-term average.

That steady value, however, has been produced on a shrinking land base. Harvested acreage exceeded 110,000 acres in 1998; by last year, that had dropped to 96,000 acres. Predictably, the value per acre has risen dramatically. Adjusted for inflation, it climbed from $8,872 in 1998 to $13,352 last year, an increase of more than 50 percent. (The figures refer to gross revenue, not profits.)

In terms of total revenue, the highest-value crops in the county are tomatoes, which generated $58,832 per acre last year; cut flowers, $57,017; nursery stock, $55,720; and raspberries, $54,392. Not surprisingly, three of those crops saw major gains in acreage (cut flowers were the exception). Beans were the lowest-value crop in the county (excluding hay), bringing only $1,699 an acre — helping explain why they long ago ceased to be the county's leading commodity.

The shift to higher-value crops is not solely the result of growers making the economically rational decision to maximize profits. It also reflects the increasing cost of land, labor, water, energy and other critical inputs, which in this pricey corner of the world set a very high minimum requirement for the revenue a grower must generate to stay in business. And that's where the long-term implications of the annual crop reports become somewhat gloomy.

Even high-value crops start bringing less money when too many growers plant too many acres of them, causing prices to fall as supply exceeds demand. That appears to be happening already with strawberries, the county's top crop. And, eventually, there won't be a higher-value crop to plant in all that open ground. What then?

Greenhouse space increased by 776,000 square feet between 2005 and 2005, a jump of 14 percent. If that's the future of farming in Ventura County, tomorrow's residents may be hard-pressed to tell the difference between cities and the agricultural land separating them.

— John Krist is a senior editor and Opinion columnist for The Star. View previous columns at www.johnkrist.com. His e-mail address is jkrist@VenturaCountyStar.com.