Prairie farmers are feeling nervous and it’s not just about the weather. It’s the news: The soybean crop in Brazil, the drought in Australia and now the endless bulletins about the political turmoil in Ukraine. The last one is the wild card, because Ukraine is a big grain producer and a leading exporter. It is ranked third in global market share in corn and sixth in wheat production. In fact, it is the main supplier of corn, wheat and rapeseed to Europe. On Wednesday, Chicago wheat futures soared to a 10-month high.