(Adds planting estimates, closing prices, paragraphs 5-8)

* Drier weather expected to benefit U.S. wheat harvest

* Soybeans fall after crop conditions top expectations

* Crop ratings expected to be steady to higher next week

By Tom Polansek

CHICAGO, June 24 (Reuters) – U.S. wheat futures slid to a four-month low on Tuesday as the country’s advancing harvest increased supplies, while soybean futures dropped on better-than-expected U.S. crop conditions.

Weather conditions are expected to improve for the wheat harvest in the U.S. Plains after recent rains slowed progress.

The U.S. Department of Agriculture said in a weekly crop report on Monday that harvest was 33 percent complete, despite some rain delays. That topped analyst estimates for 28 percent and the five-year average of 31 percent.

“Upcoming rains won’t be heavy or prolonged,” said Rich Feltes, vice president of research for brokerage RJ O’Brien.

Front-month wheat futures closed down 1.5 percent, or 8-3/4 cents, to $5.70-1/2 a bushel on the Chicago Board of Trade. The contract earlier hit $5.70, the lowest since February 7.

Front-month soybean futures lost 0.8 percent, or 11-1/4 cents, to $14.14-3/4 a bushel. Spot corn futures shed 0.4 percent, or 1-3/4 cents, to $4.42-3/4 a bushel.

Traders are expected to adjust positions in the markets before the USDA on June 30 issues separate estimates for crop plantings and grain stocks as of June 1.

The USDA will likely increase its estimate for corn seedings by 0.04 percent from March to 91.725 million acres and its estimate for soybean seedings by 0.8 percent to 82.154 million, according to a Reuters survey of analysts.

“The market knows there is a lot of corn coming and that will set a lower tone for prices as we head toward harvest,” said Kayla Burkhart, broker for SunPrairie Grain in North Dakota.

Condition ratings for corn and soy are expected to be steady or improve next week owing to favorable weather.

The USDA last rated 72 percent of the soy crop as good to excellent, down a percentage point from the prior week because of heavy rains but higher than most analysts had expected.

The corn crop was rated 74 percent good to excellent, down 2 percentage points from the week before, but still above the five-year average of about 68 percent for late June.

Prices at 1:57 p.m. CDT (1857 GMT)                           
 
                              LAST      NET    PCT     
                                        CHG    CHG     
 CBOT corn                  442.75    -1.75  -0.4%    
 CBOT soy                  1414.75   -11.25  -0.8%    
 CBOT meal                  449.30    -7.40  -1.6%    
 CBOT soyoil                 40.86     0.29   0.7%    
 CBOT wheat                 570.50    -8.75  -1.5%   
 
 (Additional reporting by Colin Packham in Sydney and Sybille de
LaHamaide in Paris; Editing by Keiron Henderson, Meredith
Mazzilli and Tom Brown)