Urban Pasture Chickens and Nutrient Management.

Keeping a small flock of layers is becoming increasingly popular and is raising concerns about sustainability of nutrient management with backyard poultry.  A flock of ten laying hens is enough to supply all the eggs needed for an average size family.  If one considers that there are about 35 million acres of lawn in the USA, there is abundant opportunity for keeping small flocks of chickens on grass.  If all 344 million egg layers in the USA were kept on home turf, there would be only about ten chickens grazing on each acre of lawn.  In 2011, I recorded values on feed consumption and egg production from my own flock.  Daily feed intake was 0.3156 lbs feed per hen.  The birds generally lay large eggs with an average weight of 0.165 lbs.  During the summer months when days are long, birds have an average laying rate of 80%.  But in the winter months when day length is short the laying rate is only about 50%.  Typical analysis of feed = 2.66% N, 0.6% P, 0.84%K.  Typical analysis of egg = 1.92% N, 0.21% P, 0.12%K.  Based on calculations, most of the NPK contained in feed is diverted to the manure which in effect is added to the soil over the area that is grazed.  Ten chickens, with a 50% laying rate, pastured on an acre would deposit per acre in one year 24.8 lbs N, 6.3 lbs P, and 9.3 lbs K.  These amounts of NPK applied in the form of chicken manure do not appear to be excessive, at least in the short term.  A backyard poultry flock would likely apply less N per year as manure that a typical lawn fertilizer application.  If necessary, nutrient balance could be maintained by collecting and composting lawn clippings.