Hydroponic systems: Hype or new perspective

Over the past five to ten years internationally a renewed interest can be observed in systems that require little or no substrate, such as deep flow technique and nutrient film technique - here dubbed hydroponic systems. Interestingly these systems have been around for over 40 years, but have only locally developed into main stream growing systems, mainly in Australia and Asia. This paper addresses the questions of what drives this renewed interest, why these systems haven't developed earlier - like for example stone wool-based systems - and whether hydroponic systems are reliable enough for sustainable, large scale introduction. We analysed case material of regional transition processes in horticultural production systems from over the past 50 years. We analysed the processes according to 1) the need for change in horticulture at the time - the main drivers, 2) the knowledge system available, 3) the knowledge available and 4) the windows of opportunity for introduction. Early adoption to hydroponic systems in the '70s led to system failures due to lack of knowledge of nutrient management, the role of oxygen, systematic design approaches, an over-focus on logistical solutions and disease management. By the time most of these issues were understood - in the '80s - the interest in hydroponic systems had made way for substrate-based systems in most areas of the world. Insights in disease management, emission reduction and a deeper understanding of root physiology however, have remained under-developed. Looking at the knowledge system surrounding successful introductions like the stone wool-based systems in the '80s, we find well-funded extension services to help growers adjust to the new systems and open-source innovation. Substrate-less systems largely lacked such support and lacked knowledge exchange due to large distances between first users. Extension activities were funded by governments as well as supplying companies with a vision for return on investment based on patents. For (easy to copy) hydroponic systems such knowledge protection was not available. Over the last 5-10 years a number of suppliers acquired knowledge protection through inventions on logistical aspects of the systems. We conclude that the renewed interest has a number of regional drivers such as depletion of land and societal interest in urban farming. However, to make hydroponic systems a lasting success, research effort should focus on reliable production: disease management, emission reduction and root development. Following, growers will need support to learn to operate these systems successfully. Given the current high needs, the international research interest and new forms of IP protection for suppliers, the time seems ripe for new, hydroponic systems to emerge.