The main purpose of agriculture is food production. There are always limited resources available for food production, thus the resource efficiency is always the key issue. The modern agriculture is using resources like external nutrients (fertilizers) and non renewable energy in large scale. The high production intensity results in high production per hectare, on the other hand it results also in serious environmental harms.Organic farming is based on more internal and renewable resources than conventional farming.Very often it results also in lower production intensity and lower production per hectare. There is a common criticism against organic agriculture as inefficient use of land and also inefficient use of nutrients and energy per output unit. Closer scrutiny indicates far too often, that the system boundaries and definition of production system explain the results rather than the fundamentals of different production systems. Someexamples of these types of misleading factors are purchased fodder (e.g. production area and input resources for that are partly or fully ignored) and partial nutrient system, e.g. comparison between artificial nitrogen fertilizers and farm yard manure (FYM), i.e. primary nutrients and secondary nutrients (=FYM) are compared, despite of fact that no secondary nutrients exist without primary nutrients.In this survey the whole production system is introduced and all the main nutrient flows are presented. Integration between the animal husbandry and crop production is supported by diverse crop rotation and nutrient recycling in form of FYM. High recourse efficiency is reached and environmental harms can be highly reduced by ERA-farmin
