A grain combine harvester mows sunflowers in a field owned by the "Zavet Ilyicha" collective farm, some 70 km (43 miles) south of Rostov-on-Don in Russia's Rostov region, September 6, 2010. Moscow on Monday gave another mixed signal about the duration of a grain export ban set initially from August 15 to December 31, but European Union grain markets continued to rise, apparently ignoring the latest twist. REUTERS/Vladimir Konstantinov (RUSSIA - Tags: AGRICULTURE BUSINESS)