Closing nutrient cycles in Dutch organic farming: an explorative scenario study of agronomic consequences

Given the principles of organic agriculture, nutrient cycling in Dutch organic farming can be characterised as imperfect, mainly because of large imports of nutrients from conventional agriculture and from abroad. Recently, research has been initiated into the perspectives for better closing nutrient cycles by intensifying the exchange of (by-)products between organic farming sectors. The linear programming model was developed to quantify under different scenarios the agronomic consequences of further closing nutrient cycles in terms of changes in land use and exchange of (by-)products. Better closing of nutrient cycles requires an increase in the proportion of Dutch feed ingredients in animal diets, an increase in the proportion of feed and leguminous crops in rotations, an increase in the export of manure from the organic dairy sector and an increase of the import of `acceptable¿ nutrients from society. Depending on the sector and the degree in which `undesirable¿ nutrient imports are banned, current sizes of the main farming sectors will have to change to be in equilibrium, i.e. a situation in which total organic manure production determines organic crop areas and crop productivity per ha and vice versa. Closing nutrient cycles will result in an extensification of Dutch organic farming and an increase in cost prices.