GRAINS-Soybeans rise on strong demand, wheat rises for second day

* Soybeans rise for three out of four sessions

* Strong demand, concerns about S.American crop support

* Wheat underpinned by shrinking crop in Australia

(Adds details, quotes) SINGAPORE, Sept 18 (Reuters) - Chicago soybean futures rose on Monday for the third session out of four on expectations of strong demand from China although the expanding harvest in the United States kept a lid on the market. Wheat edged higher, holding on to Friday's 1.4 percent gain on concerns over lower production in Australia, the world's fourth-largest exporter. The Chicago Board of Trade most-active soybean contract gained 0.5 percent to $9.73-1/2 a bushel by 0326 GMT, wheat rose 0.1 percent $4.49-1/2 a bushel and corn was unchanged at $3.54-3/4 a bushel. Export demand is lending support to soybeans. The U.S. Department of Agriculture said on Friday that private exporters sold 132,000 tonnes of U.S. soybeans to China, the latest in a string of U.S. soybean sales announced last week. Cash values for soybeans continued to firm at the U.S. Gulf, supported by exporters seeking beans for September loadings.

In addition, Argentina's 2017/18 soybean harvest is expected to fall by as much as 7 percent to 52 million tonnes compared with the 2016/17 crop year, local agriculture analysts said on Friday, citing low profit margins and excess water caused by heavy rains. "Demand is going to be strong and that is a known factor," said one India-based agricultural commodities analyst. "But what is uncertain is the weather. There is talk about La Nina impacting crops in Brazil and Argentina." The gain in soybean prices was capped by expectations of expanding harvest progress in the U.S. Midwest in the coming days. Drier weather in the eastern U.S. Midwest and the Mississippi Delta region will favor corn and soybean drydown and early harvesting, the MDA Weather Services said in a note to clients. For wheat, the Australian government last week cut its estimate of the country's 2017/18 harvest to 21.64 million tonnes, an eight-year low. Looking at the next year, private analytics firm Informa Economics expects U.S. farmers in 2018 to devote more acres to corn and wheat and fewer to soybeans, according to an Informa client note. The firm projected U.S. 2018 corn plantings at 91.880 million acres, up from its estimate of 90.660 million seeded in 2017, according to the note dated Thursday and seen by Reuters on Friday.

Grains prices at 0326 GMT

Contract Last Change Pct chg Two-day chg MA 30 RSI CBOT wheat 449.50 0.50 +0.11% +1.47% 446.54 76 CBOT corn 354.75 0.00 +0.00% +0.14% 361.54 66 CBOT soy 973.50 4.75 +0.49% -0.26% 950.96 68 CBOT rice 12.86 $0.05 +0.39% +0.35% $12.66 68 WTI crude 49.92 $0.03 +0.06% +0.06% $48.17 67


Euro/dlr $1.194 $0.000 +0.02% +0.21% USD/AUD 0.8025 0.002 +0.30% +0.25%

Most active contracts Wheat, corn and soy US cents/bushel. Rice: USD per hundredweight RSI 14, exponential

(Reporting by Naveen Thukral; Editing by Christian Schmollinger)