U.S. wheat futures sank to contract lows, weighed down by abundant global supplies and technical selling as prices extended a fall that started in early July. Traders are tracking the annual Farm Journal Midwest Crop Tour, which found below-average corn yield potential in Indiana and above-average in Nebraska while soybean pod counts were average to below-average in the states. Rainfall in the Midwest was expected to benefit both corn and soybean fields and crop-friendly weather in recent weeks continued to anchor prices.