"Commercial" urban egg farms?

Old Oregon Agricultural College research, predicated on non-use of artificial inputs or treatments (other than liming the houses and treating chicken parasites). I assume the author of this piece is thinking humane and organic. In the old days of yarded poultry - 1,000 to an acre - liming the soil was a regular occupation and green feed was provided by soiling. (Soiling is where you grow green and other feed for the chickens in a plot and feed it to them where the pasture is poor, or where the concentration of chickens is too high for pasturing them.)

On a thousand square feet you could possibly range maybe two dozen hens because fewer biddies and a smaller plot means you could intensively managed and divide into yards. Two yards, each 12.5' x 50' are considered sufficient for a dozen hens if they are alternated between pasture for the chickens (which will be gone in mere weeks) and intensive cultivation of food for the family and soiling for the chickens. You plant a fall pasture crop on last years garden and move the biddies when it is tall enough to resist them in the spring and then move the biddies and immediately turn their former yard into this year's garden.

Soon about 625 square feet you could pasture maybe a dozen to fifteen hens and not destroy the soil, so you might be able to range two dozen hens on a thousand square feet. Divide it into three yards, with one for garden and two used as pasture at any point, and you might get up to three dozen.

Oh - some modern keepers use more yards and faster rotations, but you need to have about a year before bringing birds back on a yard. They use higher stocking values, but it can be really hard on the ground; a soft soil is a lot better than a clay soil for this purpose, probably moderately sandy soil would be best as it drains faster.

Then there is the question of what the nitrates are doing to the ground water.