By Maximilian HeathBUENOS AIRES, Sept. 19 (Reuters) - Argentina's exports of grains and their byproducts could hit a record 105.1 million metric tons in the 2025/26 season, the Rosario grains exchange said on Friday. That would top the 101.6 million tons of exports logged in the previous season as well as the record 104.1 million tons in the 2018/19 season, according to the exchange. In its report, the exchange projected shipments of grains and oilseeds at 64.7 million tons, with 62% being corn sales. Exports of oils and meals, meanwhile, were estimated at 40.4 million tons, with the vast majority derived from soybeans. Farmers began planting corn over the past several weeks, with soybean planting to start in October.