Grain and soy futures were slammed like most other commodity markets and closed sharply lower. The reaction to the devaluation of the yuan masked the market's attitude on the last full trading day before the August WASDE. General Comments What Monday gives, Tuesday takes away. Today took away most of Monday's big jump in soybean and corn futures prices and all of wheat's gains plus more. Turnaround Tuesday had major help from China's central bank, which devalued the yuan by 1.9 percent, the biggest downward move in about 20 years. The bank also indicated that it would allow market forces to play a larger role in valuing the currency. That was seen as bankspeak hinting that further devaluations may be forthcoming. World markets generally s...