The close-up range of laying hen houses under the nutrient aspect - better-practice farms and model studies on suitable substrates (2017-2018)

The keeping of laying hens is of great economic importance for organic agriculture in Germany. Compared to other forms of organic livestock farming, it has the highest share of total German production, at around 10%. The free-range management of laying hens is an absolute eye-catcher for marketing with pictures of lush green runs on which fully feathered hens cavort. However, the 4 m² minimum regulation, which has been in place since 2000, is proving increasingly problematic, especially when uneven use of the area by the animals leads to local pollution of the soil and plant growth. In the case of laying hen houses that remain on one site for a longer period of time, there is a conflict of objectives: on the one hand, the animals should be allowed to roam as much as possible, and on the other hand, eutrophication of the run, especially with nitrogen and phosphorus, should be avoided, which subsequently leads to leaching or outgassing - at least in the case of nitrogen - and thus runs counter to the environmental objectives of organic farming. The focus of the investigations is the N-dynamics in the outdoor area of stationary laying hen houses. In four- to six-week intervals, the dynamics of NH4-N and NO3-N are recorded as a function of the different zones. The project also includes a substrate trial in which five substrates and five additives are tested for their ability to bind nutrients or to reduce or prevent their entry into the soil. Over the winter seepage period, the dynamics of NH4-N and NO3-N are determined in eight-week cycles.