Mineralenbelasting van de kippenuitloop : kippenuitloop gezond en groen

A high input of minerals could be a undesired effect of the chickens’ outdoor run. As part of the project ‘Uitloop Gezond en Groen’ (Outdoor run Healthy and Green), realized in 2006 – 2008, the soil of the outdoor run of four organic poultry farms was analysed on phosphorus, nitrogen and heavy metals. Beside this, absorption of minerals by means of straw in the outdoor run was monitored and the phosphorus balances of two farms were calculated. There indeed is a net input of minerals: close to the stables higher concentrations of phosphorus and heavy metals are found, compared to parts at more distance. Within these two years no increase of phosphorus concentration was measured although it could be expected according to calculations. This will be caused by a combination of factors: the input may be overestimated, soil and minerals might return to the stable sticking to the paws or in the intestines of the chickens, and a structural bias in the sampling may have occurred. Straw could be used to reduce mineral accumulation close to the stable, but several disadvantages are connected to this way of working. Removal of soil is effective, but in conflict with permanent ‘green cover’ . The farm phosphorus balances are unreliable due to unreliable phosphorus calculations of the dung. Both sampling and analysis are source of faults