The latest sales data from the Association of Equipment Manufacturers (AEM) shows total U.S. 2-wheel drive tractor sales gained four percent for March compared to last year, while 4-wheel drive tractors sales dropped five percent. Self-propelled combine sales declined 20 percent. First-quarter 2018 U.S. sales were essentially flat for the smaller-size tractors and 100-plus HP 2-wheel drive tractors declined about …