NAPERVILLE, Illinois, June 25 (Reuters) - Speculators were forced to abandon more short positions in Chicago grains and oilseeds last week as U.S. crop health further deteriorated under an exceptional dry spell.

In the four-day week ended June 20, money managers erased a combined 100,000 gross short positions across CBOT corn, wheat, soybeans, soy products, Kansas City and Minneapolis wheat, the most for any week since August 2020.

Money managers also added 45,000 gross longs last week, the most in four months and driven primarily by corn, where new longs outnumbered short covering.

Net buying in soybeans last week was split between new longs and short covering, though funds’ latest moves in CBOT wheat and soybean oil were exclusively the result of short covering.

In the week ended June 20, money managers extended their net long in CBOT corn futures and options to 58,299 contracts from 2,145 in the prior week, establishing their most bullish view since Feb. 28.

They also increased their net long in CBOT soybeans to a two-month high of 76,950 futures and options contracts versus 47,882 a week earlier. Both new-crop corn and soybean futures rose more than 8% in the week ended June 20 amid near-record dryness in top-producing U.S. states.

Money managers increased their net long in CBOT soybean oil futures and options to 29,817 contracts through June 20 from 8,748 in the prior week on near 8% gains in December soyoil futures. Funds’ net soyoil buying in the latest two weeks was the strongest for any two-week period since February 2019.

July and December CBOT wheat futures both rose more than 9% through June 20, and money managers cut their net short position to a 17-week low of 84,134 futures and options contracts from 113,430 a week earlier. Short covering for the week was the strongest since May 2019.

December soybean meal climbed almost 7% in the week ended June 20, but funds’ net reaction was relatively muted as their net long increased by about 3,300 to 63,924 futures and options contracts.

AFTERMATH OF FALLING CROP CONDITIONS

After the market closed on June 20, both U.S. corn and soybean conditions fell below the range of analyst guesses for the week. At the same time, U.S. biofuel blending volumes mandated by the Environmental Protection Agency were immediately seen as disappointing, weighing on the soy complex.

U.S. corn was only 55% good or excellent as of June 18, the week’s worst since 1992 and the lowest for any June or July week since 2012. December corn made a new yearly high of $6.29-3/4 per bushel Wednesday, taking out the prior high of $6.11 set Jan. 3.

November soybeans topped out Wednesday at $13.78 per bushel, their highest since March 8, but below the Jan. 3 high of $14.15-3/4.

Weather forecasts late last week increased rain hopes for parched U.S. crops, easing futures. December corn and November soybeans fell 1.6% and 2.4%, respectively, over the last three sessions.

December soybean oil shed 4.7% between Wednesday and Friday and December meal lost 1.1%, but nearby and deferred CBOT wheat futures added 5% on global supply concerns, especially in the United States and the Black Sea. Karen Braun is a market analyst for Reuters. Views expressed above are her own.

(Editing by Lisa Shumaker)