* For the week, CBOT corn dropped 2.4 percent, breaking a streak of five straight weekly increases. * Analytical firm Informa Economics raised its forecast of 2012 US corn plantings to 94.0 million acres -- the most since 1944 -- from its previous outlook of 93.1 million, trade sources said. * Rainfall early next week will slow the final harvest of US corn and soybeans while the Plains wheat crop enters winter dormancy in better shape due to recent rains, an agricultural meteorologist said on Friday. * Investment bank Goldman Sachs on Thursday said it raised its price forecast for corn in response to strong domestic demand and the US Department of Agriculture's reduced estimate of the US corn crop.