During the 20th century, agricultural engineering became a really multidisciplinary "eld of science. Besides traditional mechanical engineering, fundamental developments in microelectronics, systems and control engineering, chemical engineering and physics have opened wide perspectives for agricultural engineering. During the last century, agricultural engineering has e!ected major changes in agriculture with regard to labour productivity and specialization in the di!erent sectors of plant production and livestock production. Public concern for environmental issues, e.g. emissions of volatile compounds, water pollution through plant nutrients and agrochemicals, has resulted in research and technology development in the "eld of environmental engineering. In developing activities for more sustainability in production, agricultural enterprises have to reclaim the trust of society and earn &the licence to produce'! Agricultural engineers have the chances to contribute in this process. They must be also aware that new technologies and techniques require thorough full technology assessment procedure to make clear aspects of acceptability to di!erent groups in the community. To achieve optimal results for agribusiness and the society, the expertise of agricultural engineers must be integrated with expertise from the biological and socio-economic sciences. In agricultural engineering, a dynamic balance between economy, technology and ecology must always be found in order to satisfy the requirements of government and the changing preferences of consumers. Recognition of trends in the society and networking and participation in debates are important activities for agricultural engineers in the 21st century. &Breakthrough' technologies are needed for agricultural enterprises to meet the increasing list of standards and norms, for example in the areas of energy, animal welfare, product quality, water and volatile emissions.
As this was the case in the last century, agricultural engineering has therefore to keep pace with trends in science and technology, e.g. fundamental developments in the information and communication technology, biotechnology, materials technology, microelectronics and mechatronics. Technology watch, networking and cooperation are key words for agricultural engineers.
In line with these challenges, strategic themes for the agricultural engineering science are: the concepts for sustainable bioproduction systems in the greenhouse and livestock sector; the further progress in precision agriculture; the use of biomass and wastes as energy sources: electronic communication with models and databases without human interference (green net); and innovative measurement and biomonitoring systems.