Farmers in southern New Hampshire say this year’s corn crop is shaping up to be a good one. The first early corn of the season was for sale at farmers’ markets in Derry and Atkinson this week. But there is some concern about dry weather. Gail McWilliam-Jellie, director of the state’s Division of Agriculture Development, told the Eagle-Tribune in Lawrence that there are pockets of the state where crops are starting to show stress from dry conditions. However, it is not as severe as the drought in the Midwest. Weather could make the crop better or worse, said Melissa Dolloff, manager of the farm stand at J&F Farms in Derry. ‘‘So far, it looks really good,’’ Dolloff said. ‘‘But we need some rain. We’re running out of water to water it.’’