I free range my flock - 50+ poultry, 4.5 acres +/-, 1.75 acres of that as pasture. I've a long growing season and biodiverse polycultural pasture. They get 18% complete commercial feed with free choice oyster shell to provide needed calcium for the layers. Free ranging cuts my feed need 25-30%.
Can NOT join the other posters who suggested corn, or corn and scratch, as adequate feed. Those are filler and treats, respectively. While I have no idea as to your flock management plans in terms of how long you plan to keep your birds before replacement, or the nutritional value of your pasture, even in the moderately short term I'd be concerned about your flock obtaining a balanced, nutritionally complete diet. Corn for instance is missing both Lysine and Tryptophan, two critical amino acids for poultry development, and its niacin is bound in an indigestible form. Scratch is generally low protien (8-9%), high fat, and typically contains a lot of... you guessed it, corn.
Scratch frequently contains BOSS - black oil sunflower seeds - cause they are cheap and high protein, but also high fat, and often other seeds besides. As a class, seeds tend to be low in lysine, just like corn. Your Scratch is probably filled out with some other grains, which as a class tend to be low in lysine and threonine - but at least oats tend to be (relatively) high in tryptophan, helping to balance the corn somewhat. To get that missing lysine from the plant world??? Soy or fenugreek are among the best sources. Doubtful either is in your Scratch. Lysine is not, unlike some, an amino acid the chicken can produce on its own.
They are your birds, you are welcome to roll your dice and take your chances - but the available science and studies do not support a cracked corn only or corn and scratch deit supplimented by whatever is found in your fields, seasonally. At least, not if you want your birds to be in optimal health from a feed standpoint.