Just like they led all grains higher earlier in the week, soybeans are now leading all grains lower.

Early calls for the grains are corn 2 cents lower to 2 cents higher, wheat 3-5 cents lower and soybeans 8-10 lower, according to private sources. 

In overnight trading, March corn was 1/2 cent lower at $6.43 per bushel, March wheat was 3 1/4 cents lower at $6.48 and January soybeans, leading the downturn, were 9 3/4  cents lower at 11.88 1/2, according to Barchart.com.

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The deflating prices continue as profit-taking trips up the grains from sharp gains earlier in the week on the crop weather stress situation in South America. Tuesday's trade saw soybeans soar almost 37 cents per bushel by the closing bell, but since then, gains have been trimmed by profit-taking and spreading, analysts and traders say.

On top of that, there are rainfall chances in the forecast for parts of Brazil, though expected rainfall totals will fall short of an inch, one forecast says, and that's well short of what the crops need.

• See more: Brazil soybeans weather
• Photo: Cordoba, Argentina, corn field