The Department of Agriculture has granted preliminary approval for a large-scale plan to grow genetically altered rice in Kansas, prompting some critics to raise safety concerns. Ventria Bioscience, based in Sacramento, Calif., wants to grow rice modified to produce human proteins on more than 3,000 acres of farmland near Junction City. The pharmaceutical rice would be harvested and refined for use in medicines to fight diarrhea, dehydration and other illnesses that kill millions of infants and toddlers each year.