Preheat oven to 350°F and spray a 9 x 5 x 3 inch loaf pan with nonstick cooking spray.
Whisk together sugar, milk, oil, vanilla, yogurt, egg and lemon zest in a large bowl. Stir together dry ingredients an 3/4 cup walnuts and add to bowl, stirring just until dry ingredients are incorporarted (do not over mix). Carefully fold in blackberries and spead into prepared pan; sprinkle with remaining walnuts.
Bake for 1 hour and 20 minutes or until a toothpick inserted into the center comes out clean.