The fallout is a rare chink in Lopez Obrador's formidable popularity, steadily above 60% throughout his term.
The pricing issue is urgent as northern corn farmers are harvesting now, many with nowhere to sell without taking a loss.
It is not the first time that tensions have heated up between this administration and the agriculture sector.
Valdez estimated that commercial agriculture producers represent about 10 million votes.
Farmers argue Lopez Obrador's government has eliminated important sector benefits, including loans at beneficial interest rates, which his administration says too often fell into arrears.
Persons:
Edgard Garrido, Andres Manuel Lopez, Lopez, Lopez Obrador's, Bosco, la Vega, Lopez Obrador, Claudia Sheinbaum, Marcelo Ebrard, Adan Augusto, Baltazar Valdez, Valdez, Raul Urteaga, Urteaga, spokespeople, Luz Maria Mendoza, Cassandra Garrison, Stephen Eisenhammer, Nick Zieminski
Organizations:
REUTERS, MEXICO CITY, U.S, Regeneration, Producers, Chicago Board of Trade, CNA, Farmers, North American Free Trade, United Farm Workers, Valdez, Global Agrotrade Advisors, Agriculture, Finance Ministry, FIRA, Thomson
Locations:
La Constitucion Totoltepec, Toluca , Mexico, MEXICO, Sinaloa, United States, U.S, Chihuahua, Mexico, Canada