Stir together sour cream and water in small saucepan. Heat over low heat until temperature reaches 120° to 130°F. Do not boil. Combine 2 cups flour, yeast, sugar, salt and baking soda in large bowl. Spread sour cream mixture evenly over flour mixture with rubber spatula. Stir until well blended. Turn out dough onto lightly floured surface. Turn out onto lightly floured surface. Knead about 5 minutes adding enough of remaining flour to make a smooth and elastic dough.
Grease large baking sheet. Shape dough into ball; place on prepared sheet. Flatten into 8-inch circle. Brush top with oil. Sprinkle with poppy seeds. Invert large bowl over dough and let rise in warm place 1 hour or until doubled in bulk.
Preheat oven to 350°F. Bake 22 to 27 minutes or until golden brown. Remove immediately from baking sheet; cool on wire rack.