Corn, soy show "renewed vigor" on low crop forecasts

* Corn, soybeans end three-day retreat

* Farm Futures pegs U.S. corn crop below 10 billion bushels

* Traders eye poor weather hurting Russian wheat crop

By Tom Polansek

CHICAGO, Aug 3 (Reuters) - U.S. corn and soybean futures ended a three-day slide on Friday as private crop forecasts reignited supply concerns by projecting output will fall well below government estimates due to poor weather.

A Farm Futures Magazine survey of more than 1,800 U.S. farmers pegged the U.S. 2012 corn crop at 9.57 billion bushels, 26 percent below the U.S. Department of Agriculture's current forecast.

The government is expected to reduce its projection next week.

The markets were "showing some renewed vigor on supportive private-sector forecasts," said Rich Feltes, senior vice president of research for R.J. O'Brien.

Markets had pulled back in the past three days in a retreat from record highs reached last month on increasing concerns about the worst drought in 50 years hurting U.S. output.

Wheat also pushed higher on Friday on speculation dry weather in Russia could lead to export restrictions in the Black Sea producer.

Russia shocked global grain markets in 2010 by banning wheat exports due to a severe drought.

"Some analysts believe Russia will be out of the wheat export business before end of year, forcing wheat buyers to other origins," Feltes said.

Chicago Board of Trade new-crop December corn rose 9-1/2 cents, or 1.2 percent, to $8.05-1/4 per bushel by 9:50 a.m. EDT (1450 GMT), while actively traded November soy gained 11-1/2 cents, or 0.7 percent, to $16.28.

September wheat climbed 18 cents, or 2.1 percent, to $8.83 per bushel.

UNCERTAINTY OVER RUSSIAN EXPORTS

There is caution in the market ahead of the USDA's supply-demand report on Aug. 10 that could further cut the government's yield and production estimates for U.S. corn and soybeans while revising down its demand forecasts.

Some expect the USDA to slash its estimate of the number of acres of corn that will be harvested due to severe damage from the drought, which covers about two-thirds of the contiguous United States.

"There are concerns that yields are going to be down, so people don't want to be short ahead of the USDA report," said Abah Ofon, an analyst at Standard Chartered Bank in Singapore.

"Even if there is profit-taking, the downside is going to be limited."

The drought-hit U.S. Midwest is feeling a little relief, as storms in the last day brought much-needed rain to parched corn and soybean crops in eastern areas and more was forecast through the weekend, an agricultural meteorologist said.

The moisture arrived too late to offer much help to corn crops in the area but should give a boost to soybeans, which are in their key pod-setting phase.

In Russia, forecasters pointed to hot and dry weather dominating in August, which could further diminish crop prospects.

Investment bank Goldman Sachs said it saw growing upside risks to wheat prices in the coming months due to continued dry weather in countries such as Argentina, India, Australia and the former Soviet Union.

After differing estimates given by Russian government officials this week, operators are looking ahead to an Aug. 8 meeting of a food security body for clearer indications on the country's harvest.

An apparent downgrade in the official outlook for the grain harvest has added to market talk that Russia could resort to some sort of export restriction, two years after it banned grain shipments in the wake of a severe drought.

Prices at 9:51 a.m. CDT (1451 GMT)

                             LAST      NET    PCT     YTD
                                        CHG    CHG     CHG
 CBOT corn                  805.75    11.75   1.5%   24.6%
 CBOT soy                  1662.00     9.00   0.5%   38.7%
 CBOT meal                  529.90     6.20   1.2%   71.3%
 CBOT soyoil                 51.99     0.45   0.9%   -0.2%
 CBOT wheat                 885.75    20.75   2.4%   35.7%
 CBOT rice                 1595.00     7.50   0.5%    9.2%
 EU wheat                   260.75     4.25   1.7%   28.8%
 
 US crude                    90.61     3.48   4.0%   -8.3%
 Dow Jones                  13,085      207   1.6%    7.1%
 Gold                      1596.71     6.97   0.4%    2.1%
 Euro/dollar                1.2327   0.0147   1.2%   -4.8%
 Dollar Index              82.6400  -0.7210  -0.9%    3.1%
 Baltic Freight                852       -9  -1.1%  -51.0%
 
 (Additional reporting by Naveen Thukral in Singapore and Gus
Trompiz in Paris; Editing by Dale Hudson and William Hardy)