In the main grains market of Rosario, soy prices closed up for a second session at 1,780 pesos ($355) per tonne from 1,750 pesos in the previous session, lifted by gains on the US soy futures market in Chicago, traders said.

Soybean futures on the Chicago Board of Trade ended higher Friday as traders covered short positions ahead of a three-day US holiday weekend, traders said. Support stemmed from uncertainty about weather in crop areas of Argentina, where urgently needed rains were expected to fall this weekend.

Rosario soy for delivery in May 2013, which is quoted in US dollars, closed at $320 per tonne compared with between $320 and $325 per tonne on Thursday.

The scant rains and high temperatures worrying Argentine farmers since January have started to hit the development of corn and soy, particularly later-planted crops, the agriculture ministry said on Friday.