Nutrient loading on free range farms

The stocking density of farm animals is a critical factor in the long term sustainability of farmland. With chickens, the maximum outdoor stocking density of 1500 hens per hectare was established by the industry, academics, politicians and bureaucrats when they prepared the Model Code of Practice for the Welfare of Animals (Domestic Poultry). Nutrients and trace elements in manure accumulate in the soil, making it toxic for vegetation and polluting ground and surface water.

A laying hen produces half a cubic metre of manure a year. So with a stocking density of 10,000 hens per hectare approved by Ministers for Consumer Affairs earlier this year, farmers who follow their advice will see their land covered with 5000 cubic metres of manure per hectare every year. Chicken manure has the highest amount of nitrogen,phosphorus, and potassium of all manures, so will likely render the land useless for farming within a few years. Contamination of groundwater and water courses is also likely.