LAST PERSON RURAL: Essays by Noel Perrin (David R. Godine: $21.95; 199 pp.). When Noel Perrin, a professor of environmental studies at Dartmouth College, published "Third Person Rural" nine years ago, he thought it would be the last volume in his series of "country essays." Fortunately, it wasn't: Perrin attributes the existence of the current collection to remarriage and his subsequent rededication to family farming, but at bottom, one senses he simply couldn't let good material lie fallow. There's the annual hay baling, which gives Perrin's village a sense of history and common purpose; the abandoned 19th-Century factory in the woods, lost to nature; the pick-up with an electric winch, allowing Perrin not only to pull pine stumps out of pastures but strangers' cars out of ditches. Perrin is something of a gentleman farmer--he puts teaching and writing first in his autobiographical description--but since he raises cows and pigs for meat as well as growing vegetables and tapping syrup maples, it's clear that South Farm is no romantic hobby. That's most evident in the "Country Battles" section, in which Perrin describes farmers' troubles with acid rain, agribusiness and so on, but he's at his best when talking about his personal experiences as a farmer, such as weeding a hayfield organically--with cows. They ate everything but the milkweed, which Perrin eliminated by offering a two-bit bonus to the daughter who first plucked a thousand stems by hand.