Aug 1 (Reuters) -Spot basis bids for soybeans shipped by barge to the U.S. Gulf Coast firmed on Thursday amid demand from exporters as Chicago Board of Trade (CBOT) soybean futures Sv1 slid to near-four-year lows, traders said.

* Chinese buyers have been showing seasonal interest in U.S. soybeans, they said. The U.S. Department of Agriculture confirmed private sales of 132,000 metric tons of new-crop soybeans to China.

* Corn barge bids continued to sag at the Gulf, pressured by adequate corn supplies and scattered farmer sales as producers and grain handlers worked to clear space for the 2024 harvest.

* Benign crop weather and expectations of large U.S. crops weighed on futures. CBOT corn futures traded as low as $3.95 per bushel, the lowest on a continuous chart of the most-active corn contract Cv1 since November 2020, and benchmark CBOT soybean futures Sv1 dipped to $10.13 a bushel, the lowest since October 2020. GRA/

* After the CBOT close, brokerage StoneX projected the average U.S. 2024 corn yield at 182.3 bushels per acre (bpa) and the U.S. soybean yield at 52.6 bpa, both above the USDA's current forecasts.

* CIF Gulf soybean barges loaded in August were bid at 74 cents over CBOT August SQ24 soybean futures, up 2 cents from Wednesday's bid. November soybean barges traded at 80 cents over November SX24 futures, up 3 cents from Wednesday's trades.

* FOB export premiums for September Gulf soybean loadings held steady at around 115 cents over CBOT November SX24 futures. Export premiums for October loadings were 90 to 92 cents over November futures, up 2 to 5 cents from Wednesday.

* For corn, CIF Gulf barges loaded in August were bid at 66 cents over CBOT September CU24 corn futures, down 2 cents from Wednesday. September corn barges were bid at 75 cents over futures, down a penny from Wednesday.

* FOB offers for Gulf corn shipments loaded in August were around 79 cents over futures, down 1 cent from Wednesday, and September shipments were offered around 85 cents over futures, up 1 cent.

* The USDA reported U.S. old-crop corn export sales in the week to July 25 at 167,900 metric tons, a marketing year low, while new-crop corn sales totaled 710,900 tons, toward the high end of expectations. EXP/CORN

* Weekly soybean sales at 376,400 tons of old crop and 632,100 tons of new crop were near the high end of trade expectations. EXP/SOY

Reporting by Julie Ingwersen; editing by Alan Barona

For displays of CIF basis, click on the codes in brackets: U.S. CIF Gulf soybeans GRYM U.S. CIF Gulf corn GRYN U.S. CIF Gulf SRW wheat GRYO U.S. CIF Gulf HRW wheat GRYP
For displays of FOB basis, please click on the following codes in brackets: U.S. FOB Gulf corn GRZC U.S. FOB Gulf soybeans GRZD U.S. FOB Gulf SRW wheat GRZE U.S. FOB Gulf HRW wheat GRZF LINKS Corn prices page: cpurl://apps.cp./cms/?pageid=corn-cash-market
Wheat prices page: cpurl://apps.cp./cms/?pageid=wheat-cash-market
U.S. barge freight BG/US
U.S. export sales estimates USDA/EST
U.S. grain export summary GRA/U
Brazil soybean export prices SYBS
Brazil corn export prices SYBX
Argentina grain prices GRA/ARG
Russia grain prices GRA/RU