Environmental legislation is forcing a rethink about desirable crop production systems. The development of new production systems that meet economic and environmental objectives demands knowledge about which input–output combinations are feasible and optimal in practice. A review of concepts in agronomy and in farm and behavioural economics leads to a conceptual model with a division into production levels and accompanying production restricting factors. The highest production level can be defined by merely agronomic growth factors; the next production level is restricted by a mixture of economic and other agronomic factors. The two lowest levels are further restricted by taking into account the socio-psychological factors. With the production restricting factors of the conceptual model the differences in agronomic efficiency of actual and theoretical input–output combinations will be analysed in order to find out which input–output combinations will be feasible and optimal in practice.