U.S. export sales are seasonally slowing, which is impacting CBOT futures. American farmers have nonetheless had a good run. The value of the dollar is up 1.6 percent from its low at the start of the year, which further adds competitive pressure.   After nearly a four-month run of U.S. corn being cheaper than South American origin, Argentina took the lead this month as the cheapest. Brazil still faces the burden of an uncertain safrinha crop that could keep its exports below their peak in 2018/19.   

It has always been more muddled for U.S. wheat exports, which are tracking better than in the past couple of campaigns but are in overall decline. Spot FOB prices might be close but are offset by Europe’s transport...