The restricted 90-day window in which producers cannot legally sow soy to prevent the spread of Asian rust fungus, ended on Sept. 15 in the biggest soy state, Mato Grosso.

Forward sales rose to 46 percent of expected output from 45 percent the previous week, Celeres said in a weekly report. Farmers have sought to lock in high prices since the US drought spurred global supply fears. Much less of the new crop 21 percent had been sold a year earlier.

Producers have sold 98 percent of the 65-million-tonne 2011-2012 crop that ended harvest in May, unchanged from a week earlier and above the 89 percent sold by this time last year, Minas Gerais-based Celeres said.

Stocks were depleted after drought in Brazil's soy belt this year, but Celeres expects a record 78.1 million tonnes for the 2012-2013 crop from Brazil, due partly to forecasts of steadier and earlier rainfall.