FRESNO COUNTY, Calif. — For decades, the fiercely independent fruit and vegetable growers of California, Florida and other states have been the only farmers in America who shunned federal subsidies, delivering produce to the tables of millions of Americans on their own. But now, in the face of tough new competition primarily from China, even these proud groups are buckling. Produce farmers, their hands newly outstretched, have joined forces for the first time, forming a lobby group intended to pressure politicians over the farm bill to be debated in Congress in January. Nobody disputes that competitive pressures from abroad are...