GERMANTOWN, N.Y. — Dennis Nesel converts barley to malt the way it was done hundreds of years ago, spreading the water-soaked grain on his malt house floor and turning it with a shovel as it germinates to release the sugar needed for fermentation. “This is old-school heritage malting,” says Nesel, whose “micro malt house” uses barley from a nearby farm and returns some of it as malt to the farm’s craft brewing operation, which turns out small batches of beer sold at farmer’s markets and local pubs. Nesel’s Hudson Valley Malt, 100 miles north of New York City, is one of dozens of small malting businesses that have sprung up around the country over the past few years to serve a growing thirst for locally crafted beer and whiskey that reflect a region’s climate and soils. “Wine people call it terroir,” Nesel said.