Rising commodity prices and scarce land for sale are pushing valley farmland values to record levels, economists and land appraisers say.

And it isn't just the best farmland that is fetching top dollar. Marginal land with limited water is also in demand as investors see great potential to make big bucks growing some of the region's new hot crops.

Recently, two large parcels of land in west Fresno County sold for between $8,000 and $10,000 an acre, about double what land in that area was selling for a year ago.

"We are watching with amazement what is going on out there," said Dan Errotabere, of Riverdale-based Errotabere Ranches and a longtime west-side farmer.

Errotabere was among more than 150 people attending Wednesday's 2013 Fresno Agriculture Valuation Symposium held at Fresno State's Gazarian Real Estate Center.

Experts said the valley mirrors the rest of the state and nation, with farmland values rising steadily over the past several years as crop values rise and farmers hang on to their property.

In California, the average price for farmland rose about 4 percent to $7,200 an acre in 2012 -- the highest price ever.

"There is no question that demand is exceeding supply," said Dale Samuelian, a senior vice president at Pearson Realty in Fresno. "No one wants to sell, and that only makes the prices go higher."

What farmers and investors are after is land to plant some of the hottest crops in the valley: nuts, wine grapes and to some degree mandarins.

Of the two west-side parcels sold recently, wine grapes will be planted on a 3,400-acre ranch and almonds will be planted on 5,300 acres.

Samuelian said major considerations for development, such as the availability of water, aren't stopping investors. Those buying the land plan to install wells to make up for a lack of surface water.

Real estate appraiser Stan Xavier Jr. agreed, saying the demand for planting more permanent crops has helped drive up the value of land for most of the valley's major commodities, with the notable exception of dairy.

Record-high feed prices forced numerous dairies out of business last year and lowered the value of their land.

Unlike dairies, the value of nut acreage remains solid, Xavier said.

For example, almond acreage that was selling for $12,000 to $18,000 an acre in 2011 sold for more than $20,000 an acre last year.

Although the rise in farmland values follows a housing bubble that burst six years ago, at least one expert believes farm values are not likely to crash any time soon.

Mechel Paggi, economist and director of Fresno State's Center for Agricultural Business, said one positive sign for farmers is that despite the rise in farmland values -- 71 percent for California from 2000 to 2010 -- the value of the state's agricultural commodities has also steadily grown.

"It does not look like to me that land prices are inflated or out of line," Paggi said.