U.S. soybean futures fell nearly 2 percent on Friday on profit-taking after increased purchases from the United States by top soy importer China and a strike by Brazilian port workers had sent prices to a 3-1/2-month peak.
"We do have potential for the bullish weather in Argentina and bullish port strike news in Brazil to turn around over the weekend and become bearish. That brought in the front-end selling," analyst Mike Zuzolo of Global Commodity Analytics said.
Traders also said soybeans may have found pressure from a rumor that China's Sinograin could be set to release rape oil from reserves.
Soybeans were still up 2.5 percent for the week after workers at Brazil's Santos and Paranagua ports went on strike for six hours but called off industrial action previously set for Tuesday.
The profit-taking included a partial exodus of traders from the March /November (old-crop/new-crop) spread that had widened to $2.10-3/4 on Thursday, premium March, a four-month high.
The tight stocks of soybeans, brisk demand and prospects for a bumper U.S. soybean crop this year had allowed the spread to gap wider over the past several weeks. March/November closed on Friday at $1.94-1/4, premium March, a 7.6 percent retracement.
A fresh sale of U.S. soy to China rather than from Brazil boosted soybeans above the resistance level of $15 per bushel in early dealings on Friday, the first time soy has traded above that resistance point since mid-December.
The strike could shift even more soy export business to the United States and away from Brazil. The two countries are the world's No.1 and No.2 suppliers of soybeans, respectively.
"Strikes at the two big export ports, when there is already a significant backlog and harvest will soon pick up, are a serious issue," said Rich Nelson, chief strategist for Illinois-based research and advisory firm Allendale Inc.
"The U.S. will pick up a few extra orders as this issue progresses," Nelson said.
Wheat fell for the fifth consecutive week as a snowstorm in the U.S. Plains brought relief to the drought-stricken winter crop.
Corn eased on spillover from soybeans and on end-of-week positioning.
Chicago Board of Trade March soybeans were down 26-1/2 cents per bushel at $14.61-1/4, March wheat was down 6-1/4 at $7.15 and March corn was down 1/2 cent at $6.90-1/4.
Concern about dry weather in Argentina has resurfaced with little to no rainfall expected in the near term, said Andy Karst, meteorologist for World Weather Inc. "There was some light rain Wednesday and Thursday but not a lot more in drought areas of Argentina for the next two weeks," he said.
Karst said the driest areas were in southern Argentina, "especially in the southwest, which is a big corn-growing area". Overall satisfactory crop weather continues in Brazil.
"Most of Brazil is in pretty good shape," Karst said. Argentina is the world's second-largest corn producer after the United States, the third-largest soybean exporter and the largest exporter of soymeal and soyoil.
Traders said the issues in South America continued to shift soybean business to the United States, a key factor in the market's early rise above key psychological resistance at the $15 per bushel level.
"I do not discount the importance of Brazil being able to ship beans and any disruptions causing anxiety on the part of buyers, such as China," said Bill Nelson, oilseeds analyst for Doane Advisory Services in St. Louis, Missouri.
"But the market remains focused on Argentine weather too." The U.S. Department of Agriculture (USDA) on Friday said private exporters had reported the sale of 410,000 tonnes of U.S. soybeans to China.
Trade sources on Thursday told Reuters that Chinese importers have booked up to nine cargoes of U.S. soybeans this week for shipment beginning next month, with port congestion in Brazil likely to delay shipments.
"Fifteen dollars has been a key technical resistance level for soybeans on nearby continuous contracts. A close over that level or signs that is likely could be fairly bullish for those inclined to that approach," Nelson said.
Strong global demand for Brazil's big corn and soybean crops has two to three times more ships lined up to load at its two main ports than a year earlier.
Fifty-nine ships were waiting to load grain at Santos port on Thursday versus 29 a year ago, data from SA Commodities/Unimar showed. At the other main grain port, Paranagua, 82 ships were waiting compared with 31 ships this time last year.
Gains in wheat and corn were slowed by improved crop weather in the United States following the worst drought in over 50 years and on U.S. government outlooks for a strong rebound in crop production.
The U.S. corn stockpile will more than triple this year following a record harvest and the U.S. soybean crop will be a record 3.405 billion bushels, a 13 percent increase from 2012's drought-hit crop, the USDA said on Friday.