Estimates of the cost of building a wall along our 1,989-mile border with Mexico have been all over the board. $8 billion? $10 billion? $12 billion? $25 billion as the Washington Post calculates? Who knows?

Or maybe it could reach $2 trillion, judging from the estimates by a panel of experts on the Colbert Show on the CBS Television Network: http://www.nationalmemo.com/architect-engineer-build-trumps-wall/?utm_campaign=website&utm_source=sd&utm_medium=email.

What those figures don’t include is how much such a wall could cost U.S. farmers in lost sales of rice, cotton, corn and soybeans. Mexico currently is the No. 1 or No. 2 U.S. market for those commodities.

I’m aware people think the wall is a figure of speech, campaign rhetoric the president never fully intended to implement. The problem is he signed an executive order starting the process of building the wall within days of taking office. And he recently said again he was deadly serious about it.

I’m also aware part of a wall exists – the 670 miles of high-steel fencing Republicans spent $2.4 billion building. How’s that working for us, by the way?

For U.S. rice producers, the potential cost of the wall just got a little higher. A few days ago, Mexico announced it was removing the 20-percent duty on shipments of rice from Vietnam through the end of 2017.

Most observers don’t expect an immediate surge of Vietnamese milled rice into Mexico, displacing U.S. rice. Nor do other experts think Mexico could find the quantities of corn and soybeans it needs from sources other than the U.S.

The wall isn’t the only obstacle casting a shadow over trade with Mexico. The president says he intends to renegotiate the North American Free Trade Agreement, which USA Rice Federation leaders credit with helping build a 600,000-metric-ton market for U.S. rough rice..

As Dr. Mike Strain, commissioner of the Louisiana Department of Agriculture and Forestry and the current president of the National Association of State Departments of Agriculture, said in a recent speech: “We trade with countries we have agreements with,” indicating the importance of NAFTA to Louisiana producers.

At what point does Mexico become so angry with us, they back out of NAFTA? Or Cuba says it will buy from anyone but the U.S. because the current president has canceled the Obama overtures? Dr. Strain also expressed concerns about the president’s immigration policy’s impact on guest worker programs, which a number of Louisiana farmers and food processors rely on to keep their businesses operating.

Normally, the agriculture secretary would talk to White House officials and explain the situation to them. That would be difficult now because former Georgia Gov. Sonny Perdue, a grain trader himself, seems to be no closer to a confirmation hearing than he was when named for the post eight weeks ago.

For some reason that no one in the administration seems to be able to explain, the paperwork for his nomination was just submitted as this article was being posted.