SAN JUAN, Texas (AP) _ Guadalupe Lechuga has spent most of his 52 years traveling around the country picking other people's crops in fields, many tainted with toxic agricultural chemicals.

This year was different. He didn't board up the doors and windows of his home in the southern tip of Texas to travel north.

Tired of the chemicals and of working for ''los patrones'' (the bosses), Lechuga and a group of 30 migrant farm workers' families formed a cooperative to grow and market their own organic vegetables.

Lechuga, foreman of the new San Juan Farm Workers Cooperative, said the co- op's small plots of tomatoes, peppers, eggplant, squash and other vegetables represent the first time he can call a crop his own.

''I think it will be good,'' Lechuga said. ''All my life, I've had bosses.''

Like other migrants, his children year after year had to leave school in April or May to follow the work north. They typically didn't return until November, and spent their lives barely getting by.

Many migrant children never catch up in school, so they drop out. It's a way of life that keeps the Lower Rio Grande Valley, with its tens of thousands of farm workers, consistently among the poorest areas of the United States.

The co-op's goal is to pull them out of the cycle by setting them up as independent, small farmers. They're also cashing in on the growing demand for organically grown produce.

Co-op members are trained in organic farming under a project sponsored by the Texas Department of Agriculture, which also certifies the land is organic. Buyers of organic produce usually require certification by a third party, such as a state agency, to ensure it was grown without artificial chemicals.

With the training, co-op members eventually should be able to operate from their own plots of two to five acres, said Neal Warnes, the project manager, who has helped develop other organic farms.

''We're trying to get people into a line they can try to make some money at,'' Warnes said.

U.S. retail sales of organic foods reached an all-time high of $572 million in 1989, government figures show. The Texas Department of Agriculture reported $11 million in retail organic food saes in the state last year, and estimated it could increase by as much as 10-fold this year.

Organic produce supplies tend to fall short of demand at the wholesale level in Texas, said Arthur Beaudet, produce buyer for Texas Health Distributors, a subsidiary of Austin-based Whole Foods Inc., one of the largest organic-produce retailers in the United States. California organics producers are the most advanced, said Beaudet, whose company has not done business with the San Juan co-op.

Health-food restaurants and grocery co-ops in the Austin area have bought the bulk of the San Juan co-op's early crops, Warnes said.

The farm workers were stunned when a buyer paid them $1 a pound for organic tomatoes recently, more than twice the going local price, Warnes said.

''There's a health food store that would take a thousand pounds a week if we had them,'' he said.

The co-op plans to produce 28 crops in a year-round rotation; plans also include more families joining and establishing their own farms.

While they probably won't get rich, Warnes reckoned some could make up to $30,000 a year, more than double what many farm workers earn.

Some of the 30 families in the co-op had to go out of state again this summer to find work, because the operation remains small, on seven acres land owned by the United Farm Workers Union in San Juan. The co-op has access to more land when it is ready to expand, Warnes said.

Maria Gomez, 42, said she stayed behind this summer to help the co-op get started, ''to see if we can become independent, to see if we can have our own crops.''

Ms. Gomez said she has seen many farm workers fall ill from working among pesticides and chemical fertilizers, or from handling treated crops. She remembers one man whose skin on the hands and feet peeled off ''like leather. And that's on the outside. Who knows what's happening on the inside?''

Instead of chemical pesticides, the co-op uses natural substances such as rotenone, an odorless crystalline derivative of some kinds of plant roots. The co-op's natural fertilizers include seaweed and fish emulsion.

Thick walls of sunflowers surround the co-op's vegetable plots, serving as buffer zones to filter out airborne chemicals from non-organic operations in the heavily farmed valley.

The co-op's small ''family farm'' tracts and organic methods are the type promoted by environmentalists. Agribusiness proponents, however, have written off such operations as outdated and inefficient, compared to farms with hundreds or thousands of acres.

Nonetheless, the prospect of sustaining themselves with their own crops means much to people like Ms. Gomez, enthusiastic about ''everybody working together for a better way of living.''

''They're going to have their own land and they're going to be able to sell their own tomatoes, cucumbers and other crops,'' Lechuga said.

And, he said, children will be able to finish an entire year of school.