photo: flickrU.S.According to AEM, total farm tractor unit sales are up 1.5% during the first four months of 2011 and self-propelled combine sales are up 34%.CanadaAccording to AEM, total farm tractor unit sales are down 5% during the first four months of 2011 and self-propelled combine sales are up 20%.RussiaAccording to Rosagromash, self-propelled combine shipments for the first quarter of this