USDA data for weekending August 2, 2018:  Wheat:  Net sales of 317,100 MT for 2018/2019 were down 17 percent from the previous week, but up 5 percent from the prior 4-week average.   Corn:  Net sales of 554,500 MT for 2017/2018 were up 90 percent from the previous week and 33 percent from the prior 4-week average.   Soybeans:  Net sales of 421,800 MT for 2017/2018 were up noticeably from the previous week and from the prior 4-week average.   Soybean Cake and Meal:  Net sales of 109,600 MT for 2017/2018 were up 39 percent from the previous week and 6 percent from the prior 4-week average.   Soybean Oil:  Net sales of 10,900 MT for 2017/2018 were down 23 percent from t...